Merge

2018-12-13 11:51:06 -08:00 · 2018-12-13 11:51:06 -08:00 · def1ac3acc
commit def1ac3acc
parent d77f96b0b2 2880b1bb06
200 changed files with 1089 additions and 616 deletions
--- a/make/autoconf/hotspot.m4
+++ b/make/autoconf/hotspot.m4
@ -327,7 +327,7 @@ AC_DEFUN_ONCE([HOTSPOT_SETUP_JVM_FEATURES],

  # Only enable Shenandoah on supported arches
  AC_MSG_CHECKING([if shenandoah can be built])
-  if test "x$OPENJDK_TARGET_CPU_ARCH" = "xx86" || test "x$OPENJDK_TARGET_CPU" = "xaarch64" ; then
+  if test "x$OPENJDK_TARGET_CPU" = "xx86_64" || test "x$OPENJDK_TARGET_CPU" = "xaarch64" ; then
    AC_MSG_RESULT([yes])
  else
    DISABLED_JVM_FEATURES="$DISABLED_JVM_FEATURES shenandoahgc"
--- a/src/hotspot/cpu/ppc/assembler_ppc.hpp
+++ b/src/hotspot/cpu/ppc/assembler_ppc.hpp
@ -539,6 +539,12 @@ class Assembler : public AbstractAssembler {
    XVSUBDP_OPCODE = (60u << OPCODE_SHIFT |  104u << 3),
    XVMULSP_OPCODE = (60u << OPCODE_SHIFT |   80u << 3),
    XVMULDP_OPCODE = (60u << OPCODE_SHIFT |  112u << 3),
+    XVMADDASP_OPCODE=(60u << OPCODE_SHIFT |   65u << 3),
+    XVMADDADP_OPCODE=(60u << OPCODE_SHIFT |   97u << 3),
+    XVMSUBASP_OPCODE=(60u << OPCODE_SHIFT |   81u << 3),
+    XVMSUBADP_OPCODE=(60u << OPCODE_SHIFT |  113u << 3),
+    XVNMSUBASP_OPCODE=(60u<< OPCODE_SHIFT |  209u << 3),
+    XVNMSUBADP_OPCODE=(60u<< OPCODE_SHIFT |  241u << 3),

    // Deliver A Random Number (introduced with POWER9)
    DARN_OPCODE    = (31u << OPCODE_SHIFT |  755u << 1),
@ -2227,6 +2233,12 @@ class Assembler : public AbstractAssembler {
  inline void xvsubdp(  VectorSRegister d, VectorSRegister a, VectorSRegister b);
  inline void xvmulsp(  VectorSRegister d, VectorSRegister a, VectorSRegister b);
  inline void xvmuldp(  VectorSRegister d, VectorSRegister a, VectorSRegister b);
+  inline void xvmaddasp(VectorSRegister d, VectorSRegister a, VectorSRegister b);
+  inline void xvmaddadp(VectorSRegister d, VectorSRegister a, VectorSRegister b);
+  inline void xvmsubasp(VectorSRegister d, VectorSRegister a, VectorSRegister b);
+  inline void xvmsubadp(VectorSRegister d, VectorSRegister a, VectorSRegister b);
+  inline void xvnmsubasp(VectorSRegister d, VectorSRegister a, VectorSRegister b);
+  inline void xvnmsubadp(VectorSRegister d, VectorSRegister a, VectorSRegister b);

  // VSX Extended Mnemonics
  inline void xxspltd(  VectorSRegister d, VectorSRegister a, int x);
--- a/src/hotspot/cpu/ppc/assembler_ppc.inline.hpp
+++ b/src/hotspot/cpu/ppc/assembler_ppc.inline.hpp
@ -790,6 +790,12 @@ inline void Assembler::xvadddp( VectorSRegister d, VectorSRegister a, VectorSReg
 inline void Assembler::xvsubdp( VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVSUBDP_OPCODE | vsrt(d) | vsra(a) | vsrb(b)); }
 inline void Assembler::xvmulsp( VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVMULSP_OPCODE | vsrt(d) | vsra(a) | vsrb(b)); }
 inline void Assembler::xvmuldp( VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVMULDP_OPCODE | vsrt(d) | vsra(a) | vsrb(b)); }
+inline void Assembler::xvmaddasp( VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVMADDASP_OPCODE  | vsrt(d) | vsra(a) | vsrb(b)); }
+inline void Assembler::xvmaddadp( VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVMADDADP_OPCODE  | vsrt(d) | vsra(a) | vsrb(b)); }
+inline void Assembler::xvmsubasp( VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVMSUBASP_OPCODE  | vsrt(d) | vsra(a) | vsrb(b)); }
+inline void Assembler::xvmsubadp( VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVMSUBADP_OPCODE  | vsrt(d) | vsra(a) | vsrb(b)); }
+inline void Assembler::xvnmsubasp(VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVNMSUBASP_OPCODE | vsrt(d) | vsra(a) | vsrb(b)); }
+inline void Assembler::xvnmsubadp(VectorSRegister d, VectorSRegister a, VectorSRegister b) { emit_int32( XVNMSUBADP_OPCODE | vsrt(d) | vsra(a) | vsrb(b)); }
 inline void Assembler::mtvrd(   VectorRegister d, Register a)               { emit_int32( MTVSRD_OPCODE  | vsrt(d->to_vsr()) | ra(a)); }
 inline void Assembler::mfvrd(   Register        a, VectorRegister d)         { emit_int32( MFVSRD_OPCODE  | vsrt(d->to_vsr()) | ra(a)); }
 inline void Assembler::mtvrwz(  VectorRegister  d, Register a)               { emit_int32( MTVSRWZ_OPCODE | vsrt(d->to_vsr()) | ra(a)); }
--- a/src/hotspot/cpu/ppc/ppc.ad
+++ b/src/hotspot/cpu/ppc/ppc.ad
@ -2257,6 +2257,9 @@ const bool Matcher::match_rule_supported(int opcode) {
    return SuperwordUseVSX;
  case Op_PopCountVI:
    return (SuperwordUseVSX && UsePopCountInstruction);
+  case Op_FmaVF:
+  case Op_FmaVD:
+    return (SuperwordUseVSX && UseFMA);
  case Op_Digit:
  case Op_LowerCase:
  case Op_UpperCase:
@ -14475,6 +14478,92 @@ instruct vpopcnt4I_reg(vecX dst, vecX src) %{
  ins_pipe(pipe_class_default);
 %}

+// --------------------------------- FMA --------------------------------------
+// dst + src1 * src2
+instruct vfma4F(vecX dst, vecX src1, vecX src2) %{
+  match(Set dst (FmaVF dst (Binary src1 src2)));
+  predicate(n->as_Vector()->length() == 4);
+
+  format %{ "XVMADDASP   $dst, $src1, $src2" %}
+
+  size(4);
+  ins_encode %{
+    __ xvmaddasp($dst$$VectorSRegister, $src1$$VectorSRegister, $src2$$VectorSRegister);
+  %}
+  ins_pipe(pipe_class_default);
+%}
+
+// dst - src1 * src2
+instruct vfma4F_neg1(vecX dst, vecX src1, vecX src2) %{
+  match(Set dst (FmaVF dst (Binary (NegVF src1) src2)));
+  match(Set dst (FmaVF dst (Binary src1 (NegVF src2))));
+  predicate(n->as_Vector()->length() == 4);
+
+  format %{ "XVNMSUBASP   $dst, $src1, $src2" %}
+
+  size(4);
+  ins_encode %{
+    __ xvnmsubasp($dst$$VectorSRegister, $src1$$VectorSRegister, $src2$$VectorSRegister);
+  %}
+  ins_pipe(pipe_class_default);
+%}
+
+// - dst + src1 * src2
+instruct vfma4F_neg2(vecX dst, vecX src1, vecX src2) %{
+  match(Set dst (FmaVF (NegVF dst) (Binary src1 src2)));
+  predicate(n->as_Vector()->length() == 4);
+
+  format %{ "XVMSUBASP   $dst, $src1, $src2" %}
+
+  size(4);
+  ins_encode %{
+    __ xvmsubasp($dst$$VectorSRegister, $src1$$VectorSRegister, $src2$$VectorSRegister);
+  %}
+  ins_pipe(pipe_class_default);
+%}
+
+// dst + src1 * src2
+instruct vfma2D(vecX dst, vecX src1, vecX src2) %{
+  match(Set dst (FmaVD  dst (Binary src1 src2)));
+  predicate(n->as_Vector()->length() == 2);
+
+  format %{ "XVMADDADP   $dst, $src1, $src2" %}
+
+  size(4);
+  ins_encode %{
+    __ xvmaddadp($dst$$VectorSRegister, $src1$$VectorSRegister, $src2$$VectorSRegister);
+  %}
+  ins_pipe(pipe_class_default);
+%}
+
+// dst - src1 * src2
+instruct vfma2D_neg1(vecX dst, vecX src1, vecX src2) %{
+  match(Set dst (FmaVD  dst (Binary (NegVD src1) src2)));
+  match(Set dst (FmaVD  dst (Binary src1 (NegVD src2))));
+  predicate(n->as_Vector()->length() == 2);
+
+  format %{ "XVNMSUBADP   $dst, $src1, $src2" %}
+
+  size(4);
+  ins_encode %{
+    __ xvnmsubadp($dst$$VectorSRegister, $src1$$VectorSRegister, $src2$$VectorSRegister);
+  %}
+  ins_pipe(pipe_class_default);
+%}
+
+// - dst + src1 * src2
+instruct vfma2D_neg2(vecX dst, vecX src1, vecX src2) %{
+  match(Set dst (FmaVD (NegVD dst) (Binary src1 src2)));
+  predicate(n->as_Vector()->length() == 2);
+
+  format %{ "XVMSUBADP   $dst, $src1, $src2" %}
+
+  size(4);
+  ins_encode %{
+    __ xvmsubadp($dst$$VectorSRegister, $src1$$VectorSRegister, $src2$$VectorSRegister);
+  %}
+  ins_pipe(pipe_class_default);
+%}

 //----------Overflow Math Instructions-----------------------------------------

--- a/src/hotspot/cpu/x86/macroAssembler_x86_aes.cpp
+++ b/src/hotspot/cpu/x86/macroAssembler_x86_aes.cpp
@ -29,6 +29,7 @@
 #include "runtime/stubRoutines.hpp"
 #include "macroAssembler_x86.hpp"

+#ifdef _LP64
 // Multiply 128 x 128 bits, using 4 pclmulqdq operations
 void MacroAssembler::schoolbookAAD(int i, Register htbl, XMMRegister data,
    XMMRegister tmp0, XMMRegister tmp1, XMMRegister tmp2, XMMRegister tmp3) {
@ -319,4 +320,5 @@ void MacroAssembler::avx_ghash(Register input_state, Register htbl,
    vpxor(xmm1, xmm1, xmm1, Assembler::AVX_128bit);
    vpxor(xmm3, xmm3, xmm3, Assembler::AVX_128bit);
    vpxor(xmm15, xmm15, xmm15, Assembler::AVX_128bit);
-}
+}
+#endif // _LP64
--- a/src/hotspot/os/linux/os_linux.cpp
+++ b/src/hotspot/os/linux/os_linux.cpp
@ -1354,9 +1354,11 @@ void os::shutdown() {
 void os::abort(bool dump_core, void* siginfo, const void* context) {
  os::shutdown();
  if (dump_core) {
+#if INCLUDE_CDS
    if (UseSharedSpaces && DumpPrivateMappingsInCore) {
      ClassLoader::close_jrt_image();
    }
+#endif
 #ifndef PRODUCT
    fdStream out(defaultStream::output_fd());
    out.print_raw("Current thread is ");
@ -5075,9 +5077,11 @@ jint os::init_2(void) {
    set_coredump_filter(DAX_SHARED_BIT);
  }

+#if INCLUDE_CDS
  if (UseSharedSpaces && DumpPrivateMappingsInCore) {
    set_coredump_filter(FILE_BACKED_PVT_BIT);
  }
+#endif

  return JNI_OK;
 }
--- a/src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp
@ -939,9 +939,6 @@ void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint wo
  q = queues->claim_next();
  while (q != NULL) {
    if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
-      ShenandoahCancelledTerminatorTerminator tt;
-      ShenandoahSuspendibleThreadSetLeaver stsl(ShenandoahSuspendibleWorkers);
-      while (!terminator->offer_termination(&tt));
      return;
    }

@ -965,9 +962,6 @@ void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint wo
   */
  while (true) {
    if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
-      ShenandoahCancelledTerminatorTerminator tt;
-      ShenandoahSuspendibleThreadSetLeaver stsl(ShenandoahSuspendibleWorkers);
-      while (!terminator->offer_termination(&tt));
      return;
    }

@ -991,7 +985,8 @@ void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint wo
      // Need to leave the STS here otherwise it might block safepoints.
      ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
      ShenandoahTerminationTimingsTracker term_tracker(worker_id);
-      if (terminator->offer_termination()) return;
+      ShenandoahTerminatorTerminator tt(heap);
+      if (terminator->offer_termination(&tt)) return;
    }
  }
 }
--- a/src/hotspot/share/gc/shenandoah/shenandoahTaskqueue.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahTaskqueue.cpp
@ -49,28 +49,8 @@ bool ShenandoahObjToScanQueueSet::is_empty() {
  return true;
 }

-class ShenandoahOWSTTerminator: public OWSTTaskTerminator {
-public:
-  ShenandoahOWSTTerminator(uint n_threads, TaskQueueSetSuper* queue_set) :
-    OWSTTaskTerminator(n_threads, queue_set){ }
-
-protected:
-  bool exit_termination(size_t tasks, TerminatorTerminator* terminator);
-};
-
-bool ShenandoahOWSTTerminator::exit_termination(size_t tasks, TerminatorTerminator* terminator) {
-  ShenandoahTerminatorTerminator* t = (ShenandoahTerminatorTerminator*)terminator;
-  bool force = (t != NULL) && t->should_force_termination();
-  if (force) {
-    // Force termination : continue termination, even there are remaining tasks.
-    return false;
-  } else {
-    return OWSTTaskTerminator::exit_termination(tasks, terminator);
-  }
-}
-
 ShenandoahTaskTerminator::ShenandoahTaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set) :
-  _terminator(new ShenandoahOWSTTerminator(n_threads, queue_set)) { }
+  _terminator(new OWSTTaskTerminator(n_threads, queue_set)) { }

 ShenandoahTaskTerminator::~ShenandoahTaskTerminator() {
  assert(_terminator != NULL, "Invariant");
--- a/src/hotspot/share/gc/shenandoah/shenandoahTaskqueue.hpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahTaskqueue.hpp
@ -306,18 +306,12 @@ public:
 };

 class ShenandoahTerminatorTerminator : public TerminatorTerminator {
+private:
+  ShenandoahHeap* _heap;
 public:
+  ShenandoahTerminatorTerminator(ShenandoahHeap* const heap) : _heap(heap) { }
  // return true, terminates immediately, even if there's remaining work left
-  virtual bool should_force_termination() { return false; }
-};
-
-class ShenandoahCancelledTerminatorTerminator : public ShenandoahTerminatorTerminator {
-  virtual bool should_exit_termination() {
-    return false;
-  }
-  virtual bool should_force_termination() {
-    return true;
-  }
+  virtual bool should_exit_termination() { return _heap->cancelled_gc(); }
 };

 class ShenandoahTaskTerminator : public StackObj {
--- a/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
@ -498,10 +498,6 @@ void ShenandoahTraversalGC::main_loop_work(T* cl, jushort* live_data, uint worke
  q = queues->claim_next();
  while (q != NULL) {
    if (_heap->check_cancelled_gc_and_yield(sts_yield)) {
-      ShenandoahCancelledTerminatorTerminator tt;
-      ShenandoahEvacOOMScopeLeaver oom_scope_leaver;
-      ShenandoahSuspendibleThreadSetLeaver stsl(sts_yield && ShenandoahSuspendibleWorkers);
-      while (!terminator->offer_termination(&tt));
      return;
    }

@ -547,17 +543,15 @@ void ShenandoahTraversalGC::main_loop_work(T* cl, jushort* live_data, uint worke
      ShenandoahEvacOOMScopeLeaver oom_scope_leaver;
      ShenandoahSuspendibleThreadSetLeaver stsl(sts_yield && ShenandoahSuspendibleWorkers);
      ShenandoahTerminationTimingsTracker term_tracker(worker_id);
-      if (terminator->offer_termination()) return;
+      ShenandoahTerminatorTerminator tt(_heap);
+
+      if (terminator->offer_termination(&tt)) return;
    }
  }
 }

 bool ShenandoahTraversalGC::check_and_handle_cancelled_gc(ShenandoahTaskTerminator* terminator, bool sts_yield) {
  if (_heap->cancelled_gc()) {
-    ShenandoahCancelledTerminatorTerminator tt;
-    ShenandoahEvacOOMScopeLeaver oom_scope_leaver;
-    ShenandoahSuspendibleThreadSetLeaver stsl(sts_yield && ShenandoahSuspendibleWorkers);
-    while (! terminator->offer_termination(&tt));
    return true;
  }
  return false;
--- a/src/hotspot/share/jfr/jni/jfrJniMethod.cpp
+++ b/src/hotspot/share/jfr/jni/jfrJniMethod.cpp
@ -33,7 +33,7 @@
 #include "jfr/recorder/checkpoint/jfrMetadataEvent.hpp"
 #include "jfr/recorder/checkpoint/types/traceid/jfrTraceId.inline.hpp"
 #include "jfr/recorder/repository/jfrRepository.hpp"
-#include "jfr/recorder/repository/jfrChunkSizeNotifier.hpp"
+#include "jfr/recorder/repository/jfrChunkRotation.hpp"
 #include "jfr/recorder/repository/jfrChunkWriter.hpp"
 #include "jfr/recorder/service/jfrOptionSet.hpp"
 #include "jfr/recorder/stacktrace/jfrStackTraceRepository.hpp"
@ -114,7 +114,7 @@ NO_TRANSITION(void, jfr_set_enabled(JNIEnv* env, jobject jvm, jlong event_type_i
 NO_TRANSITION_END

 NO_TRANSITION(void, jfr_set_file_notification(JNIEnv* env, jobject jvm, jlong threshold))
-  JfrChunkSizeNotifier::set_chunk_size_threshold((size_t)threshold);
+  JfrChunkRotation::set_threshold((intptr_t)threshold);
 NO_TRANSITION_END

 NO_TRANSITION(void, jfr_set_sample_threads(JNIEnv* env, jobject jvm, jboolean sampleThreads))
@ -173,6 +173,9 @@ NO_TRANSITION(jboolean, jfr_set_cutoff(JNIEnv* env, jobject jvm, jlong event_typ
  return JfrEventSetting::set_cutoff(event_type_id, cutoff_ticks) ? JNI_TRUE : JNI_FALSE;
 NO_TRANSITION_END

+NO_TRANSITION(jboolean, jfr_should_rotate_disk(JNIEnv* env, jobject jvm))
+  return JfrChunkRotation::should_rotate() ? JNI_TRUE : JNI_FALSE;
+NO_TRANSITION_END

 /*
 * JVM_ENTRY_NO_ENV entries
--- a/src/hotspot/share/jfr/jni/jfrJniMethod.hpp
+++ b/src/hotspot/share/jfr/jni/jfrJniMethod.hpp
@ -129,6 +129,9 @@ jboolean JNICALL jfr_set_cutoff(JNIEnv* env, jobject jvm, jlong event_type_id, j

 void JNICALL jfr_emit_old_object_samples(JNIEnv* env, jobject jvm, jlong cutoff_ticks, jboolean);

+jboolean JNICALL jfr_should_rotate_disk(JNIEnv* env, jobject jvm);
+
+
 #ifdef __cplusplus
 }
 #endif
--- a/src/hotspot/share/jfr/jni/jfrJniMethodRegistration.cpp
+++ b/src/hotspot/share/jfr/jni/jfrJniMethodRegistration.cpp
@ -78,7 +78,8 @@ JfrJniMethodRegistration::JfrJniMethodRegistration(JNIEnv* env) {
      (char*)"setForceInstrumentation", (char*)"(Z)V", (void*)jfr_set_force_instrumentation,
      (char*)"getUnloadedEventClassCount", (char*)"()J", (void*)jfr_get_unloaded_event_classes_count,
      (char*)"setCutoff", (char*)"(JJ)Z", (void*)jfr_set_cutoff,
-      (char*)"emitOldObjectSamples", (char*)"(JZ)V", (void*)jfr_emit_old_object_samples
+      (char*)"emitOldObjectSamples", (char*)"(JZ)V", (void*)jfr_emit_old_object_samples,
+      (char*)"shouldRotateDisk", (char*)"()Z", (void*)jfr_should_rotate_disk
    };

    const size_t method_array_length = sizeof(method) / sizeof(JNINativeMethod);
--- a/src/hotspot/share/jfr/leakprofiler/emitEventOperation.cpp
+++ b/src/hotspot/share/jfr/leakprofiler/emitEventOperation.cpp
@ -185,7 +185,7 @@ static int array_size(const oop object) {
  if (object->is_array()) {
    return arrayOop(object)->length();
  }
-  return -1;
+  return min_jint;
 }

 void EmitEventOperation::write_event(const ObjectSample* sample, EdgeStore* edge_store) {
--- a/src/hotspot/share/jfr/metadata/metadata.xml
+++ b/src/hotspot/share/jfr/metadata/metadata.xml
@ -65,19 +65,19 @@
    <Field type="InflateCause" name="cause" label="Monitor Inflation Cause" description="Cause of inflation" />
  </Event>

-  <Event name="BiasedLockRevocation" category="Java Application" label="Biased Lock Revocation" description="Revoked bias of object" thread="true"
+  <Event name="BiasedLockRevocation" category="Java Virtual Machine, Runtime" label="Biased Lock Revocation" description="Revoked bias of object" thread="true"
    stackTrace="true">
    <Field type="Class" name="lockClass" label="Lock Class" description="Class of object whose biased lock was revoked" />
    <Field type="ulong" name="safepointId" label="Safepoint Identifier" relation="SafepointId" />
    <Field type="Thread" name="previousOwner" label="Previous Owner" description="Thread owning the bias before revocation" />
  </Event>

-  <Event name="BiasedLockSelfRevocation" category="Java Application" label="Biased Lock Self Revocation" description="Revoked bias of object biased towards own thread"
+  <Event name="BiasedLockSelfRevocation" category="Java Virtual Machine, Runtime" label="Biased Lock Self Revocation" description="Revoked bias of object biased towards own thread"
    thread="true" stackTrace="true">
    <Field type="Class" name="lockClass" label="Lock Class" description="Class of object whose biased lock was revoked" />
  </Event>

-  <Event name="BiasedLockClassRevocation" category="Java Application" label="Biased Lock Class Revocation" description="Revoked biases for all instances of a class"
+  <Event name="BiasedLockClassRevocation" category="Java Virtual Machine, Runtime" label="Biased Lock Class Revocation" description="Revoked biases for all instances of a class"
    thread="true" stackTrace="true">
    <Field type="Class" name="revokedClass" label="Revoked Class" description="Class whose biased locks were revoked" />
    <Field type="boolean" name="disableBiasing" label="Disable Further Biasing" description="Whether further biasing for instances of this class will be allowed" />
@ -350,7 +350,7 @@
    <Field type="ulong" contentType="bytes" name="recentMutatorAllocationSize" label="Recent Mutator Allocation Size"
      description="Mutator allocation during mutator operation in the most recent interval" />
    <Field type="long" contentType="millis" name="recentMutatorDuration" label="Recent Mutator Duration" description="Time the mutator ran in the most recent interval" />
-    <Field type="double" name="recentAllocationRate" label="Recent Allocation Rate" description="Allocation rate of the mutator in the most recent interval in bytes/second" />
+    <Field type="double" contentType="bytes-per-second" name="recentAllocationRate" label="Recent Allocation Rate" description="Allocation rate of the mutator in the most recent interval in bytes/second" />
    <Field type="long" contentType="millis" name="lastMarkingDuration" label="Last Marking Duration" description="Last time from the end of the last initial mark to the first mixed GC" />
  </Event>

@ -362,7 +362,7 @@
    <Field type="ulong" contentType="bytes" name="ihopTargetOccupancy" label="IHOP Target Occupancy" description="Internal target old generation occupancy to reach at the start of mixed GC" />
    <Field type="ulong" contentType="bytes" name="currentOccupancy" label="Current Occupancy" description="Current old generation occupancy" />
    <Field type="ulong" contentType="bytes" name="additionalBufferSize" label="Additional Buffer" description="Additional buffer size" experimental="true" />
-    <Field type="double" name="predictedAllocationRate" label="Predicted Allocation Rate" description="Current predicted allocation rate for the mutator in bytes/second" />
+    <Field type="double" contentType="bytes-per-second" name="predictedAllocationRate" label="Predicted Allocation Rate" description="Current predicted allocation rate for the mutator in bytes/second" />
    <Field type="long" contentType="millis" name="predictedMarkingDuration" label="Predicted Marking Duration"
      description="Current predicted time from the end of the last initial mark to the first mixed GC" />
    <Field type="boolean" name="predictionActive" label="Prediction Active" description="Indicates whether the adaptive IHOP prediction is active" />
@ -564,9 +564,9 @@
      relation="SafepointId" />
  </Event>

-  <Event name="Shutdown" category="Java Virtual Machine, Runtime" label="VM Shutdown" description="VM shutting down" thread="true" stackTrace="true"
+  <Event name="Shutdown" category="Java Virtual Machine, Runtime" label="JVM Shutdown" description="JVM shutting down" thread="true" stackTrace="true"
    startTime="false">
-    <Field type="string" name="reason" label="Reason" description="Reason for VM shutdown" />
+    <Field type="string" name="reason" label="Reason" description="Reason for JVM shutdown" />
  </Event>

  <Event name="ObjectAllocationInNewTLAB" category="Java Application" label="Allocation in new TLAB" description="Allocation in new Thread Local Allocation Buffer"
@ -582,7 +582,7 @@
    <Field type="ulong" contentType="bytes" name="allocationSize" label="Allocation Size" />
  </Event>

-  <Event name="OldObjectSample" category="Java Application" label="Old Object Sample" description="A potential memory leak" stackTrace="true" thread="true"
+  <Event name="OldObjectSample" category="Java Virtual Machine, Profiling" label="Old Object Sample" description="A potential memory leak" stackTrace="true" thread="true"
    startTime="false" cutoff="true">
    <Field type="Ticks" name="allocationTime" label="Allocation Time" />
    <Field type="ulong" contentType="bytes" name="lastKnownHeapUsage" label="Last Known Heap Usage" />
@ -647,8 +647,8 @@
  <Event name="CPUTimeStampCounter" category="Operating System, Processor" label="CPU Time Stamp Counter" period="endChunk">
    <Field type="boolean" name="fastTimeEnabled" label="Fast Time" />
    <Field type="boolean" name="fastTimeAutoEnabled" label="Trusted Platform" />
-    <Field type="long" name="osFrequency" label="OS Frequency Per Second" />
-    <Field type="long" name="fastTimeFrequency" label="Fast Time Frequency per Second" />
+    <Field type="long" contentType="hertz" name="osFrequency" label="OS Frequency" />
+    <Field type="long" contentType="hertz" name="fastTimeFrequency" label="Fast Time Frequency" />
  </Event>

  <Event name="CPULoad" category="Operating System, Processor" label="CPU Load" description="OS CPU Load" period="everyChunk">
@ -663,13 +663,13 @@
  </Event>

  <Event name="ThreadContextSwitchRate" category="Operating System, Processor" label="Thread Context Switch Rate" period="everyChunk">
-    <Field type="float" name="switchRate" label="Switch Rate" description="Number of context switches per second" />
+    <Field type="float" contentType="hertz" name="switchRate" label="Switch Rate" description="Number of context switches per second" />
  </Event>

  <Event name="NetworkUtilization" category="Operating System, Network" label="Network Utilization" period="everyChunk">
    <Field type="NetworkInterfaceName" name="networkInterface" label="Network Interface" description="Network Interface Name"/>
-    <Field type="long" contentType="bytes" name="readRate" label="Read Rate" description="Number of incoming bytes per second"/>
-    <Field type="long" contentType="bytes" name="writeRate" label="Write Rate" description="Number of outgoing bytes per second"/>
+    <Field type="long" contentType="bits-per-second" name="readRate" label="Read Rate" description="Number of incoming bits per second"/>
+    <Field type="long" contentType="bits-per-second" name="writeRate" label="Write Rate" description="Number of outgoing bits per second"/>
  </Event>

  <Event name="JavaThreadStatistics" category="Java Application, Statistics" label="Java Thread Statistics" period="everyChunk">
@ -687,7 +687,7 @@
  <Event name="ClassLoaderStatistics" category="Java Application, Statistics" label="Class Loader Statistics" period="everyChunk">
    <Field type="ClassLoader" name="classLoader" label="Class Loader" />
    <Field type="ClassLoader" name="parentClassLoader" label="Parent Class Loader" />
-    <Field type="ulong" contentType="address" name="classLoaderData" label="ClassLoaderData pointer" description="Pointer to the ClassLoaderData structure in the JVM" />
+    <Field type="ulong" contentType="address" name="classLoaderData" label="ClassLoaderData Pointer" description="Pointer to the ClassLoaderData structure in the JVM" />
    <Field type="long" name="classCount" label="Classes" description="Number of loaded classes" />
    <Field type="ulong" contentType="bytes" name="chunkSize" label="Total Chunk Size" description="Total size of all allocated metaspace chunks (each chunk has several blocks)" />
    <Field type="ulong" contentType="bytes" name="blockSize" label="Total Block Size" description="Total size of all allocated metaspace blocks (each chunk has several blocks)" />
@ -741,8 +741,7 @@
  <Event name="ModuleExport" category="Java Virtual Machine, Runtime, Modules" label="Module Export" thread="false" period="everyChunk">
    <Field type="Package" name="exportedPackage" label="Exported Package" />
    <Field type="Module" name="targetModule" label="Target Module"
-      description="Module to which the package is qualifiedly exported.
-             If null, the package is unqualifiedly exported" />
+      description="Module to which the package is qualifiedly exported. If null or N/A, the package is unqualifiedly exported" />
  </Event>

  <Event name="CompilerStatistics" category="Java Virtual Machine, Compiler" label="Compiler Statistics" thread="false" period="everyChunk" startTime="false">
@ -1096,7 +1095,7 @@
    <Field type="OldObjectArray" name="array" label="Array Information" description="Array or null if it is not an array" />
    <Field type="OldObjectField" name="field" label="Field Information" description="Field or null if it is an array" />
    <Field type="OldObject" name="object" label="Object" description="Object holder for this reference" />
-    <Field type="int" name="skip" label="Skip value" description="The object is this many hops away" />
+    <Field type="int" name="skip" label="Skip Value" description="The object is this many hops away" />
  </Type>

  <Type name="StackFrame">
@ -1134,13 +1133,16 @@
  <XmlType name="char" javaType="char" parameterType="char" fieldType="char"/> 
  <XmlType name="string" javaType="java.lang.String" parameterType="const char*" fieldType="const char*"/> 
 
-  <XmlContentType name="bytes" annotationType="jdk.jfr.DataAmount" annotationValue="BYTES" />
-  <XmlContentType name="tickstamp" annotationType="jdk.jfr.Timestamp" annotationValue="TICKS" />
-  <XmlContentType name="epochmillis" annotationType="jdk.jfr.Timestamp" annotationValue="MILLISECONDS_SINCE_EPOCH" />
-  <XmlContentType name="tickspan" annotationType="jdk.jfr.Timespan" annotationValue="TICKS" />
-  <XmlContentType name="address" annotationType="jdk.jfr.MemoryAddress" />
-  <XmlContentType name="percentage" annotationType="jdk.jfr.Percentage" />
-  <XmlContentType name="millis" annotationType="jdk.jfr.Timespan" annotationValue="MILLISECONDS" />
-  <XmlContentType name="nanos" annotationType="jdk.jfr.Timespan" annotationValue="NANOSECONDS" />
-  
+  <XmlContentType name="bytes" annotation="jdk.jfr.DataAmount(BYTES)" />
+  <XmlContentType name="tickstamp" annotation="jdk.jfr.Timestamp(TICKS)" />
+  <XmlContentType name="epochmillis" annotation="jdk.jfr.Timestamp(MILLISECONDS_SINCE_EPOCH)" />
+  <XmlContentType name="tickspan" annotation="jdk.jfr.Timespan(TICKS)" />
+  <XmlContentType name="address" annotation="jdk.jfr.MemoryAddress" />
+  <XmlContentType name="percentage" annotation="jdk.jfr.Percentage" />
+  <XmlContentType name="millis" annotation="jdk.jfr.Timespan(MILLISECONDS)" />
+  <XmlContentType name="nanos" annotation="jdk.jfr.Timespan(NANOSECONDS)" />
+  <XmlContentType name="hertz" annotation="jdk.jfr.Frequency" />
+  <XmlContentType name="bytes-per-second" annotation="jdk.jfr.DataAmount(BYTES), jdk.jfr.Frequency" />
+  <XmlContentType name="bits-per-second" annotation="jdk.jfr.DataAmount(BITS), jdk.jfr.Frequency" />
+ 
 </Metadata>
--- a/src/hotspot/share/jfr/metadata/metadata.xsd
+++ b/src/hotspot/share/jfr/metadata/metadata.xsd
@ -107,8 +107,7 @@
          <xs:element name="XmlContentType">
            <xs:complexType>
              <xs:attribute name="name" type="xs:NMTOKEN" use="required" />
-              <xs:attribute name="annotationType" type="xs:NMTOKEN" use="required" />
-              <xs:attribute name="annotationValue" type="xs:string" use="optional" />
+              <xs:attribute name="annotation" type="xs:string" use="required" />
            </xs:complexType>
          </xs:element>
          <xs:element name="Relation">
--- a/src/hotspot/share/jfr/periodic/jfrNetworkUtilization.cpp
+++ b/src/hotspot/share/jfr/periodic/jfrNetworkUtilization.cpp
@ -174,8 +174,8 @@ void JfrNetworkUtilization::send_events() {
        event.set_starttime(cur_time);
        event.set_endtime(cur_time);
        event.set_networkInterface(entry.id);
-        event.set_readRate(read_rate);
-        event.set_writeRate(write_rate);
+        event.set_readRate(8 * read_rate);
+        event.set_writeRate(8 * write_rate);
        event.commit();
      }
      // update existing entry with new values
--- a/src/hotspot/share/jfr/recorder/repository/jfrChunkSizeNotifier.cpp
+++ b/src/hotspot/share/jfr/recorder/repository/jfrChunkSizeNotifier.cpp
@ -24,29 +24,15 @@

 #include "precompiled.hpp"
 #include "jfr/jni/jfrJavaSupport.hpp"
+#include "jfr/recorder/repository/jfrChunkRotation.hpp"
 #include "jfr/recorder/repository/jfrChunkWriter.hpp"
-#include "jfr/recorder/repository/jfrChunkSizeNotifier.hpp"

-size_t JfrChunkSizeNotifier::_chunk_size_threshold = 0;
+static jobject chunk_monitor = NULL;
+static intptr_t threshold = 0;
+static bool rotate = false;

-void JfrChunkSizeNotifier::set_chunk_size_threshold(size_t bytes) {
-  _chunk_size_threshold = bytes;
-}
-
-size_t JfrChunkSizeNotifier::chunk_size_threshold() {
-  return _chunk_size_threshold;
-}
-
-static jobject new_chunk_monitor = NULL;
-
-// lazy install
-static jobject get_new_chunk_monitor(Thread* thread) {
-  static bool initialized = false;
-  if (initialized) {
-    assert(new_chunk_monitor != NULL, "invariant");
-    return new_chunk_monitor;
-  }
-  assert(new_chunk_monitor == NULL, "invariant");
+static jobject install_chunk_monitor(Thread* thread) {
+  assert(chunk_monitor == NULL, "invariant");
  // read static field
  HandleMark hm(thread);
  static const char klass[] = "jdk/jfr/internal/JVM";
@ -55,19 +41,41 @@ static jobject get_new_chunk_monitor(Thread* thread) {
  JavaValue result(T_OBJECT);
  JfrJavaArguments field_args(&result, klass, field, signature, thread);
  JfrJavaSupport::get_field_global_ref(&field_args, thread);
-  new_chunk_monitor = result.get_jobject();
-  initialized = new_chunk_monitor != NULL;
-  return new_chunk_monitor;
+  chunk_monitor = result.get_jobject();
+  return chunk_monitor;
 }

-void JfrChunkSizeNotifier::notify() {
+// lazy install
+static jobject get_chunk_monitor(Thread* thread) {
+  return chunk_monitor != NULL ? chunk_monitor : install_chunk_monitor(thread);
+}
+
+static void notify() {
  Thread* const thread = Thread::current();
-  JfrJavaSupport::notify_all(get_new_chunk_monitor(thread), thread);
+  JfrJavaSupport::notify_all(get_chunk_monitor(thread), thread);
 }

-void JfrChunkSizeNotifier::release_monitor() {
-  if (new_chunk_monitor != NULL) {
-    JfrJavaSupport::destroy_global_jni_handle(new_chunk_monitor);
-    new_chunk_monitor = NULL;
+void JfrChunkRotation::evaluate(const JfrChunkWriter& writer) {
+  assert(threshold > 0, "invariant");
+  if (rotate) {
+    // already in progress
+    return;
+  }
+  assert(!rotate, "invariant");
+  if (writer.size_written() > threshold) {
+    rotate = true;
+    notify();
  }
 }
+
+bool JfrChunkRotation::should_rotate() {
+  return rotate;
+}
+
+void JfrChunkRotation::on_rotation() {
+  rotate = false;
+}
+
+void JfrChunkRotation::set_threshold(intptr_t bytes) {
+  threshold = bytes;
+}
--- a/src/hotspot/share/jfr/recorder/repository/jfrChunkSizeNotifier.hpp
+++ b/src/hotspot/share/jfr/recorder/repository/jfrChunkSizeNotifier.hpp
@ -22,24 +22,23 @@
 *
 */

-#ifndef SHARE_VM_JFR_RECORDER_REPOSITORY_JFRRCHUNKSIZENOTIFIER_HPP
-#define SHARE_VM_JFR_RECORDER_REPOSITORY_JFRRCHUNKSIZENOTIFIER_HPP
+#ifndef SHARE_VM_JFR_RECORDER_REPOSITORY_JFRCHUNKROTATION_HPP
+#define SHARE_VM_JFR_RECORDER_REPOSITORY_JFRCHUNKROTATION_HPP

 #include "memory/allocation.hpp"

+class JfrChunkWriter;
+
 //
 // Responsible for notifications about current chunk size now exceeding threshold.
-// This is a means to initiate a chunk rotation on the basis of size written.
+// This is a means to initiate a chunk rotation on the basis of the size written.
 //
-class JfrChunkSizeNotifier : AllStatic {
-  friend class JfrRecorder;
- private:
-  static size_t _chunk_size_threshold;
-  static void release_monitor();
+class JfrChunkRotation : AllStatic {
 public:
-  static void set_chunk_size_threshold(size_t bytes);
-  static size_t chunk_size_threshold();
-  static void notify();
+  static void evaluate(const JfrChunkWriter& writer);
+  static void set_threshold(intptr_t bytes);
+  static bool should_rotate();
+  static void on_rotation();
 };

-#endif // SHARE_VM_JFR_RECORDER_REPOSITORY_JFRRCHUNKSIZENOTIFIER_HPP
+#endif // SHARE_VM_JFR_RECORDER_REPOSITORY_JFRCHUNKROTATION_HPP
--- a/src/hotspot/share/jfr/recorder/service/jfrRecorderService.cpp
+++ b/src/hotspot/share/jfr/recorder/service/jfrRecorderService.cpp
@ -28,7 +28,7 @@
 #include "jfr/recorder/jfrRecorder.hpp"
 #include "jfr/recorder/checkpoint/jfrCheckpointManager.hpp"
 #include "jfr/recorder/checkpoint/jfrMetadataEvent.hpp"
-#include "jfr/recorder/repository/jfrChunkSizeNotifier.hpp"
+#include "jfr/recorder/repository/jfrChunkRotation.hpp"
 #include "jfr/recorder/repository/jfrChunkWriter.hpp"
 #include "jfr/recorder/repository/jfrRepository.hpp"
 #include "jfr/recorder/service/jfrPostBox.hpp"
@ -340,6 +340,7 @@ void JfrRecorderService::prepare_for_vm_error_rotation() {
 void JfrRecorderService::open_new_chunk(bool vm_error) {
  assert(!_chunkwriter.is_valid(), "invariant");
  assert(!JfrStream_lock->owned_by_self(), "invariant");
+  JfrChunkRotation::on_rotation();
  MutexLockerEx stream_lock(JfrStream_lock, Mutex::_no_safepoint_check_flag);
  if (!_repository.open_chunk(vm_error)) {
    assert(!_chunkwriter.is_valid(), "invariant");
@ -535,8 +536,5 @@ void JfrRecorderService::scavenge() {
 }

 void JfrRecorderService::evaluate_chunk_size_for_rotation() {
-  const size_t size_written = _chunkwriter.size_written();
-  if (size_written > JfrChunkSizeNotifier::chunk_size_threshold()) {
-    JfrChunkSizeNotifier::notify();
-  }
+  JfrChunkRotation::evaluate(_chunkwriter);
 }
--- a/src/hotspot/share/runtime/globals.hpp
+++ b/src/hotspot/share/runtime/globals.hpp
@ -501,6 +501,13 @@ define_pd_global(uint64_t,MaxRAM,                    1ULL*G);
  diagnostic(bool, AbortVMOnSafepointTimeout, false,                        \
          "Abort upon failure to reach safepoint (see SafepointTimeout)")   \
                                                                            \
+  diagnostic(bool, AbortVMOnVMOperationTimeout, false,                      \
+          "Abort upon failure to complete VM operation promptly")           \
+                                                                            \
+  diagnostic(intx, AbortVMOnVMOperationTimeoutDelay, 1000,                  \
+          "Delay in milliseconds for option AbortVMOnVMOperationTimeout")   \
+          range(0, max_intx)                                                \
+                                                                            \
  /* 50 retries * (5 * current_retry_count) millis = ~6.375 seconds */      \
  /* typically, at most a few retries are needed                    */      \
  product(intx, SuspendRetryCount, 50,                                      \
--- a/src/hotspot/share/runtime/vmThread.cpp
+++ b/src/hotspot/share/runtime/vmThread.cpp
@ -28,6 +28,7 @@
 #include "jfr/jfrEvents.hpp"
 #include "jfr/support/jfrThreadId.hpp"
 #include "logging/log.hpp"
+#include "logging/logStream.hpp"
 #include "logging/logConfiguration.hpp"
 #include "memory/resourceArea.hpp"
 #include "oops/method.hpp"
@ -197,6 +198,32 @@ void VMOperationQueue::oops_do(OopClosure* f) {
  drain_list_oops_do(f);
 }

+//------------------------------------------------------------------------------------------------------------------
+// Timeout machinery
+
+void VMOperationTimeoutTask::task() {
+  assert(AbortVMOnVMOperationTimeout, "only if enabled");
+  if (is_armed()) {
+    jlong delay = (os::javaTimeMillis() - _arm_time);
+    if (delay > AbortVMOnVMOperationTimeoutDelay) {
+      fatal("VM operation took too long: " SIZE_FORMAT " ms (timeout: " SIZE_FORMAT " ms)",
+            delay, AbortVMOnVMOperationTimeoutDelay);
+    }
+  }
+}
+
+bool VMOperationTimeoutTask::is_armed() {
+  return OrderAccess::load_acquire(&_armed) != 0;
+}
+
+void VMOperationTimeoutTask::arm() {
+  _arm_time = os::javaTimeMillis();
+  OrderAccess::release_store_fence(&_armed, 1);
+}
+
+void VMOperationTimeoutTask::disarm() {
+  OrderAccess::release_store_fence(&_armed, 0);
+}

 //------------------------------------------------------------------------------------------------------------------
 // Implementation of VMThread stuff
@ -209,12 +236,28 @@ VM_Operation*     VMThread::_cur_vm_operation   = NULL;
 VMOperationQueue* VMThread::_vm_queue           = NULL;
 PerfCounter*      VMThread::_perf_accumulated_vm_operation_time = NULL;
 const char*       VMThread::_no_op_reason       = NULL;
+VMOperationTimeoutTask* VMThread::_timeout_task = NULL;


 void VMThread::create() {
  assert(vm_thread() == NULL, "we can only allocate one VMThread");
  _vm_thread = new VMThread();

+  if (AbortVMOnVMOperationTimeout) {
+    // Make sure we call the timeout task frequently enough, but not too frequent.
+    // Try to make the interval 10% of the timeout delay, so that we miss the timeout
+    // by those 10% at max. Periodic task also expects it to fit min/max intervals.
+    size_t interval = (size_t)AbortVMOnVMOperationTimeoutDelay / 10;
+    interval = interval / PeriodicTask::interval_gran * PeriodicTask::interval_gran;
+    interval = MAX2<size_t>(interval, PeriodicTask::min_interval);
+    interval = MIN2<size_t>(interval, PeriodicTask::max_interval);
+
+    _timeout_task = new VMOperationTimeoutTask(interval);
+    _timeout_task->enroll();
+  } else {
+    assert(_timeout_task == NULL, "sanity");
+  }
+
  // Create VM operation queue
  _vm_queue = new VMOperationQueue();
  guarantee(_vm_queue != NULL, "just checking");
@ -492,6 +535,11 @@ void VMThread::loop() {
        _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned

        SafepointSynchronize::begin();
+
+        if (_timeout_task != NULL) {
+          _timeout_task->arm();
+        }
+
        evaluate_operation(_cur_vm_operation);
        // now process all queued safepoint ops, iteratively draining
        // the queue until there are none left
@ -533,6 +581,10 @@ void VMThread::loop() {

        _vm_queue->set_drain_list(NULL);

+        if (_timeout_task != NULL) {
+          _timeout_task->disarm();
+        }
+
        // Complete safepoint synchronization
        SafepointSynchronize::end();

--- a/src/hotspot/share/runtime/vmThread.hpp
+++ b/src/hotspot/share/runtime/vmThread.hpp
@ -27,6 +27,7 @@

 #include "runtime/perfData.hpp"
 #include "runtime/thread.hpp"
+#include "runtime/task.hpp"
 #include "runtime/vmOperations.hpp"

 //
@ -84,6 +85,26 @@ class VMOperationQueue : public CHeapObj<mtInternal> {
 };


+// VM operation timeout handling: warn or abort the VM when VM operation takes
+// too long. Periodic tasks do not participate in safepoint protocol, and therefore
+// can fire when application threads are stopped.
+
+class VMOperationTimeoutTask : public PeriodicTask {
+private:
+  volatile int _armed;
+  jlong _arm_time;
+
+public:
+  VMOperationTimeoutTask(size_t interval_time) :
+          PeriodicTask(interval_time), _armed(0), _arm_time(0) {}
+
+  virtual void task();
+
+  bool is_armed();
+  void arm();
+  void disarm();
+};
+
 //
 // A single VMThread (the primordial thread) spawns all other threads
 // and is itself used by other threads to offload heavy vm operations
@ -101,6 +122,8 @@ class VMThread: public NamedThread {

  static const char* _no_op_reason;

+  static VMOperationTimeoutTask* _timeout_task;
+
  static bool no_op_safepoint_needed(bool check_time);

  void evaluate_operation(VM_Operation* op);
--- a/src/java.base/share/classes/com/sun/java/util/jar/pack/Attribute.java
+++ b/src/java.base/share/classes/com/sun/java/util/jar/pack/Attribute.java
@ -996,7 +996,7 @@ class Attribute implements Comparable<Attribute> {
                            endp = cstr.indexOf(',', cp);
                            if (endp < 0)  endp = cstrlen;
                            String cstr1 = cstr.substring(cp, endp);
-                            if (cstr1.length() == 0)
+                            if (cstr1.isEmpty())
                                cstr1 = "empty";  // will fail parse
                            int value0, value1;
                            // Check for a case range (new in 1.6).
--- a/src/java.base/share/classes/com/sun/java/util/jar/pack/Driver.java
+++ b/src/java.base/share/classes/com/sun/java/util/jar/pack/Driver.java
@ -279,7 +279,7 @@ class Driver {
        junpack.properties().putAll(engProps);
        if (doRepack && newfile.equals(jarfile)) {
            String zipc = getZipComment(jarfile);
-            if (verbose && zipc.length() > 0)
+            if (verbose && !zipc.isEmpty())
                System.out.println(MessageFormat.format(RESOURCE.getString(DriverResource.DETECTED_ZIP_COMMENT), zipc));
            if (zipc.indexOf(Utils.PACK_ZIP_ARCHIVE_MARKER_COMMENT) >= 0) {
                    System.out.println(MessageFormat.format(RESOURCE.getString(DriverResource.SKIP_FOR_REPACKED), jarfile));
@ -552,7 +552,7 @@ class Driver {
            if (words.length == 0)    continue loadOptmap;
            String opt = words[0];
            words[0] = "";  // initial word is not a spec
-            if (opt.length() == 0 && words.length >= 1) {
+            if (opt.isEmpty() && words.length >= 1) {
                opt = words[1];  // initial "word" is empty due to leading ' '
                words[1] = "";
            }
@ -622,7 +622,7 @@ class Driver {
                    switch (specop) {
                    case '+':
                        // + means we want an non-empty val suffix.
-                        ok = (val.length() != 0);
+                        ok = !val.isEmpty();
                        specop = spec.charAt(sidx++);
                        break;
                    case '*':
@ -641,10 +641,10 @@ class Driver {
                    String specarg = spec.substring(sidx);
                    switch (specop) {
                    case '.':  // terminate the option sequence
-                        resultString = (specarg.length() != 0)? specarg.intern(): opt;
+                        resultString = specarg.isEmpty() ? opt : specarg.intern();
                        break doArgs;
                    case '?':  // abort the option sequence
-                        resultString = (specarg.length() != 0)? specarg.intern(): arg;
+                        resultString = specarg.isEmpty() ? arg : specarg.intern();
                        isError = true;
                        break eachSpec;
                    case '@':  // change the effective opt name
@ -655,14 +655,14 @@ class Driver {
                        val = "";
                        break;
                    case '!':  // negation option
-                        String negopt = (specarg.length() != 0)? specarg.intern(): opt;
+                        String negopt = specarg.isEmpty() ? opt : specarg.intern();
                        properties.remove(negopt);
                        properties.put(negopt, null);  // leave placeholder
                        didAction = true;
                        break;
                    case '$':  // normal "boolean" option
                        String boolval;
-                        if (specarg.length() != 0) {
+                        if (!specarg.isEmpty()) {
                            // If there is a given spec token, store it.
                            boolval = specarg;
                        } else {
--- a/src/java.base/share/classes/com/sun/net/ssl/KeyManagerFactory.java
+++ b/src/java.base/share/classes/com/sun/net/ssl/KeyManagerFactory.java
@ -153,7 +153,7 @@ public class KeyManagerFactory {
                                                 String provider)
        throws NoSuchAlgorithmException, NoSuchProviderException
    {
-        if (provider == null || provider.length() == 0)
+        if (provider == null || provider.isEmpty())
            throw new IllegalArgumentException("missing provider");
        Object[] objs = SSLSecurity.getImpl(algorithm, "KeyManagerFactory",
                                            provider);
--- a/src/java.base/share/classes/com/sun/net/ssl/SSLContext.java
+++ b/src/java.base/share/classes/com/sun/net/ssl/SSLContext.java
@ -109,7 +109,7 @@ public class SSLContext {
    public static SSLContext getInstance(String protocol, String provider)
        throws NoSuchAlgorithmException, NoSuchProviderException
    {
-        if (provider == null || provider.length() == 0)
+        if (provider == null || provider.isEmpty())
            throw new IllegalArgumentException("missing provider");
        Object[] objs = SSLSecurity.getImpl(protocol, "SSLContext",
                                            provider);
--- a/src/java.base/share/classes/com/sun/net/ssl/TrustManagerFactory.java
+++ b/src/java.base/share/classes/com/sun/net/ssl/TrustManagerFactory.java
@ -155,7 +155,7 @@ public class TrustManagerFactory {
                                                 String provider)
        throws NoSuchAlgorithmException, NoSuchProviderException
    {
-        if (provider == null || provider.length() == 0)
+        if (provider == null || provider.isEmpty())
            throw new IllegalArgumentException("missing provider");
        Object[] objs = SSLSecurity.getImpl(algorithm, "TrustManagerFactory",
                                            provider);
--- a/src/java.base/share/classes/java/io/Console.java
+++ b/src/java.base/share/classes/java/io/Console.java
@ -247,7 +247,7 @@ public final class Console implements Flushable
        String line = null;
        synchronized (writeLock) {
            synchronized(readLock) {
-                if (fmt.length() != 0)
+                if (!fmt.isEmpty())
                    pw.format(fmt, args);
                try {
                    char[] ca = readline(false);
@ -319,7 +319,7 @@ public final class Console implements Flushable
                }
                IOError ioe = null;
                try {
-                    if (fmt.length() != 0)
+                    if (!fmt.isEmpty())
                        pw.format(fmt, args);
                    passwd = readline(true);
                } catch (IOException x) {
--- a/src/java.base/share/classes/java/lang/ClassLoader.java
+++ b/src/java.base/share/classes/java/lang/ClassLoader.java
@ -1119,7 +1119,7 @@ public abstract class ClassLoader {

    // true if the name is null or has the potential to be a valid binary name
    private boolean checkName(String name) {
-        if ((name == null) || (name.length() == 0))
+        if ((name == null) || (name.isEmpty()))
            return true;
        if ((name.indexOf('/') != -1) || (name.charAt(0) == '['))
            return false;
--- a/src/java.base/share/classes/java/lang/Double.java
+++ b/src/java.base/share/classes/java/lang/Double.java
@ -1077,8 +1077,8 @@ public final class Double extends Number
    }

    /**
-     * Returns a nominal descriptor for this instance, which is the instance
-     * itself.
+     * Returns an {@link Optional} containing the nominal descriptor for this
+     * instance, which is the instance itself.
     *
     * @return an {@link Optional} describing the {@linkplain Double} instance
     * @since 12
--- a/src/java.base/share/classes/java/lang/Float.java
+++ b/src/java.base/share/classes/java/lang/Float.java
@ -989,8 +989,8 @@ public final class Float extends Number
    }

    /**
-     * Returns a nominal descriptor for this instance, which is the instance
-     * itself.
+     * Returns an {@link Optional} containing the nominal descriptor for this
+     * instance, which is the instance itself.
     *
     * @return an {@link Optional} describing the {@linkplain Float} instance
     * @since 12
--- a/src/java.base/share/classes/java/lang/Integer.java
+++ b/src/java.base/share/classes/java/lang/Integer.java
@ -1409,7 +1409,7 @@ public final class Integer extends Number
        boolean negative = false;
        Integer result;

-        if (nm.length() == 0)
+        if (nm.isEmpty())
            throw new NumberFormatException("Zero length string");
        char firstChar = nm.charAt(0);
        // Handle sign, if present
@ -1838,8 +1838,8 @@ public final class Integer extends Number
    }

    /**
-     * Returns a nominal descriptor for this instance, which is the instance
-     * itself.
+     * Returns an {@link Optional} containing the nominal descriptor for this
+     * instance, which is the instance itself.
     *
     * @return an {@link Optional} describing the {@linkplain Integer} instance
     * @since 12
--- a/src/java.base/share/classes/java/lang/Long.java
+++ b/src/java.base/share/classes/java/lang/Long.java
@ -1248,7 +1248,7 @@ public final class Long extends Number
        boolean negative = false;
        Long result;

-        if (nm.length() == 0)
+        if (nm.isEmpty())
            throw new NumberFormatException("Zero length string");
        char firstChar = nm.charAt(0);
        // Handle sign, if present
@ -1967,8 +1967,8 @@ public final class Long extends Number
    }

    /**
-     * Returns a nominal descriptor for this instance, which is the instance
-     * itself.
+     * Returns an {@link Optional} containing the nominal descriptor for this
+     * instance, which is the instance itself.
     *
     * @return an {@link Optional} describing the {@linkplain Long} instance
     * @since 12
--- a/src/java.base/share/classes/java/lang/Package.java
+++ b/src/java.base/share/classes/java/lang/Package.java
@ -397,11 +397,11 @@ public class Package extends NamedPackage implements java.lang.reflect.Annotated
    public String toString() {
        String spec = versionInfo.specTitle;
        String ver =  versionInfo.specVersion;
-        if (spec != null && spec.length() > 0)
+        if (spec != null && !spec.isEmpty())
            spec = ", " + spec;
        else
            spec = "";
-        if (ver != null && ver.length() > 0)
+        if (ver != null && !ver.isEmpty())
            ver = ", version " + ver;
        else
            ver = "";
--- a/src/java.base/share/classes/java/lang/Runtime.java
+++ b/src/java.base/share/classes/java/lang/Runtime.java
@ -403,7 +403,7 @@ public class Runtime {
     */
    public Process exec(String command, String[] envp, File dir)
        throws IOException {
-        if (command.length() == 0)
+        if (command.isEmpty())
            throw new IllegalArgumentException("Empty command");

        StringTokenizer st = new StringTokenizer(command);
--- a/src/java.base/share/classes/java/lang/String.java
+++ b/src/java.base/share/classes/java/lang/String.java
@ -664,7 +664,7 @@ public final class String
     *          object.
     */
    public int length() {
-        return value.length >> coder();
+        return isLatin1() ? value.length : value.length >> UTF16;
    }

    /**
@ -1943,8 +1943,7 @@ public final class String
     *          characters followed by the string argument's characters.
     */
    public String concat(String str) {
-        int olen = str.length();
-        if (olen == 0) {
+        if (str.isEmpty()) {
            return this;
        }
        if (coder() == str.coder()) {
@ -1956,6 +1955,7 @@ public final class String
            return new String(buf, coder);
        }
        int len = length();
+        int olen = str.length();
        byte[] buf = StringUTF16.newBytesFor(len + olen);
        getBytes(buf, 0, UTF16);
        str.getBytes(buf, len, UTF16);
@ -2316,7 +2316,7 @@ public final class String
            // Construct result
            int resultSize = list.size();
            if (limit == 0) {
-                while (resultSize > 0 && list.get(resultSize - 1).length() == 0) {
+                while (resultSize > 0 && list.get(resultSize - 1).isEmpty()) {
                    resultSize--;
                }
            }
@ -3545,8 +3545,8 @@ public final class String
    }

    /**
-     * Returns a nominal descriptor for this instance, which is the instance
-     * itself.
+     * Returns an {@link Optional} containing the nominal descriptor for this
+     * instance, which is the instance itself.
     *
     * @return an {@link Optional} describing the {@linkplain String} instance
     * @since 12
--- a/src/java.base/share/classes/java/lang/VersionProps.java.template
+++ b/src/java.base/share/classes/java/lang/VersionProps.java.template
@ -73,7 +73,7 @@ class VersionProps {
        "@@VENDOR_VERSION_STRING@@";

    private static final String vendor_version =
-        (VENDOR_VERSION_STRING.length() > 0
+        (!VENDOR_VERSION_STRING.isEmpty()
         ? " " + VENDOR_VERSION_STRING : "");

    private static final String VENDOR =
@ -95,7 +95,7 @@ class VersionProps {
        props.put("java.version.date", java_version_date);
        props.put("java.runtime.version", java_runtime_version);
        props.put("java.runtime.name", java_runtime_name);
-        if (VENDOR_VERSION_STRING.length() > 0)
+        if (!VENDOR_VERSION_STRING.isEmpty())
            props.put("java.vendor.version", VENDOR_VERSION_STRING);

        props.put("java.class.version", CLASSFILE_MAJOR_MINOR);
--- a/src/java.base/share/classes/java/lang/constant/ClassDesc.java
+++ b/src/java.base/share/classes/java/lang/constant/ClassDesc.java
@ -112,13 +112,13 @@ public interface ClassDesc
     *
     * A field type descriptor string for a non-array type is either
     * a one-letter code corresponding to a primitive type
-     * ({@code J,I,C,S,B,D,F,Z,V}), or the letter {@code L}, followed
-     * by the fully qualified binary name of a class, followed by {@code ;}.
-     * A field type descriptor for an array type is the character {@code [}
+     * ({@code "J", "I", "C", "S", "B", "D", "F", "Z", "V"}), or the letter {@code "L"}, followed
+     * by the fully qualified binary name of a class, followed by {@code ";"}.
+     * A field type descriptor for an array type is the character {@code "["}
     * followed by the field descriptor for the component type.  Examples of
-     * valid type descriptor strings include {@code Ljava/lang/String;}, {@code I},
-     * {@code [I}, {@code V}, {@code [Ljava/lang/String;}, etc.
-     * for more detail.
+     * valid type descriptor strings include {@code "Ljava/lang/String;"}, {@code "I"},
+     * {@code "[I"}, {@code "V"}, {@code "[Ljava/lang/String;"}, etc.
+     * See JVMS 4.3.2 ("Field Descriptors") for more detail.
     *
     * @param descriptor a field descriptor string
     * @return a {@linkplain ClassDesc} describing the desired class
@ -126,9 +126,15 @@ public interface ClassDesc
     * @throws IllegalArgumentException if the name string is not in the
     * correct format
     * @jvms 4.3.2 Field Descriptors
+     * @jvms 4.4.1 The CONSTANT_Class_info Structure
     */
    static ClassDesc ofDescriptor(String descriptor) {
        requireNonNull(descriptor);
+        int depth = ConstantUtils.arrayDepth(descriptor);
+        if (depth > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {
+            throw new IllegalArgumentException(String.format("Cannot create an array type descriptor with more than %d dimensions",
+                    ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS));
+        }
        return (descriptor.length() == 1)
               ? new PrimitiveClassDescImpl(descriptor)
               : new ReferenceClassDescImpl(descriptor);
@ -139,8 +145,15 @@ public interface ClassDesc
     * is described by this {@linkplain ClassDesc}.
     *
     * @return a {@linkplain ClassDesc} describing the array type
+     * @throws IllegalStateException if the resulting {@linkplain ClassDesc} would have an array rank of greater than 255
+     * @jvms 4.4.1 The CONSTANT_Class_info Structure
     */
    default ClassDesc arrayType() {
+        int depth = ConstantUtils.arrayDepth(descriptorString());
+        if (depth >= ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {
+            throw new IllegalStateException(String.format("Cannot create an array type descriptor with more than %d dimensions",
+                    ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS));
+        }
        return arrayType(1);
    }

@ -150,11 +163,14 @@ public interface ClassDesc
     *
     * @param rank the rank of the array
     * @return a {@linkplain ClassDesc} describing the array type
-     * @throws IllegalArgumentException if the rank is zero or negative
+     * @throws IllegalArgumentException if the rank is less than zero or if the rank of the resulting array type is
+     * greater than 255
+     * @jvms 4.4.1 The CONSTANT_Class_info Structure
     */
    default ClassDesc arrayType(int rank) {
-        if (rank <= 0)
-            throw new IllegalArgumentException("rank: " + rank);
+        int currentDepth = ConstantUtils.arrayDepth(descriptorString());
+        if (rank <= 0 || currentDepth + rank > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS)
+            throw new IllegalArgumentException("rank: " + currentDepth + rank);
        return ClassDesc.ofDescriptor("[".repeat(rank) + descriptorString());
    }

@ -162,6 +178,12 @@ public interface ClassDesc
     * Returns a {@linkplain ClassDesc} for a nested class of the class or
     * interface type described by this {@linkplain ClassDesc}.
     *
+     * @apiNote
+     *
+     * Example: If descriptor {@code d} describes the class {@code java.util.Map}, a
+     * descriptor for the class {@code java.util.Map.Entry} could be obtained
+     * by {@code d.nested("Entry")}.
+     *
     * @param nestedName the unqualified name of the nested class
     * @return a {@linkplain ClassDesc} describing the nested class
     * @throws NullPointerException if any argument is {@code null}
--- a/src/java.base/share/classes/java/lang/constant/Constable.java
+++ b/src/java.base/share/classes/java/lang/constant/Constable.java
@ -65,8 +65,9 @@ import java.util.Optional;
 */
 public interface Constable {
    /**
-     * Returns a nominal descriptor for this instance, if one can be
-     * constructed, or an empty {@link Optional} if one cannot be constructed.
+     * Returns an {@link Optional} containing the nominal descriptor for this
+     * instance, if one can be constructed, or an empty {@link Optional}
+     * if one cannot be constructed.
     *
     * @return An {@link Optional} containing the resulting nominal descriptor,
     * or an empty {@link Optional} if one cannot be constructed.
--- a/src/java.base/share/classes/java/lang/constant/ConstantUtils.java
+++ b/src/java.base/share/classes/java/lang/constant/ConstantUtils.java
@ -37,6 +37,7 @@ class ConstantUtils {
    /** an empty constant descriptor */
    public static final ConstantDesc[] EMPTY_CONSTANTDESC = new ConstantDesc[0];
    static final Constable[] EMPTY_CONSTABLE = new Constable[0];
+    static final int MAX_ARRAY_TYPE_DESC_DIMENSIONS = 255;

    private static final Set<String> pointyNames = Set.of("<init>", "<clinit>");

--- a/src/java.base/share/classes/java/lang/constant/package-info.java
+++ b/src/java.base/share/classes/java/lang/constant/package-info.java
@ -49,7 +49,7 @@
 * storing the value in a constant pool entry, or reconstituting the value given
 * a class loading context.  Every {@link java.lang.constant.ConstantDesc}
 * knows how to <em>resolve</em> itself -- compute the value that it describes --
- * via {@link java.lang.constant.ConstantDesc#resolveConstantDesc(java.lang.invoke.MethodHandles.Lookup)}.
+ * via {@link java.lang.constant.ConstantDesc#resolveConstantDesc(java.lang.invoke.MethodHandles.Lookup) ConstantDesc.resolveConstantDesc}.
 * This allows an API which accepts {@link java.lang.constant.ConstantDesc}
 * objects to evaluate them reflectively, provided that the classes and methods
 * referenced in their nominal description are present and accessible.
@ -68,7 +68,7 @@
 * When a bytecode-reading API encounters a constant pool entry, it can
 * convert it to the appropriate type of nominal descriptor.  For dynamic
 * constants, bytecode-reading APIs may wish to use the factory
- * {@link java.lang.constant.DynamicConstantDesc#ofCanonical(DirectMethodHandleDesc, java.lang.String, ClassDesc, ConstantDesc[])},
+ * {@link java.lang.constant.DynamicConstantDesc#ofCanonical(DirectMethodHandleDesc, java.lang.String, ClassDesc, ConstantDesc[]) DynamicConstantDesc.ofCanonical},
 * which will inspect the bootstrap and, for well-known bootstraps, return
 * a more specific subtype of {@link java.lang.constant.DynamicConstantDesc}, such as
 * {@link java.lang.Enum.EnumDesc}.
--- a/src/java.base/share/classes/java/lang/invoke/ConstantBootstraps.java
+++ b/src/java.base/share/classes/java/lang/invoke/ConstantBootstraps.java
@ -103,7 +103,7 @@ public final class ConstantBootstraps {
        if (type != Class.class) {
            throw new IllegalArgumentException();
        }
-        if (name.length() == 0 || name.length() > 1) {
+        if (name.length() != 1) {
            throw new IllegalArgumentException(String.format("not primitive: %s", name));
        }

--- a/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
+++ b/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
@ -201,7 +201,7 @@ public class MethodHandles {
            throw new IllegalAccessException(callerModule + " does not read " + targetModule);
        if (targetModule.isNamed()) {
            String pn = targetClass.getPackageName();
-            assert pn.length() > 0 : "unnamed package cannot be in named module";
+            assert !pn.isEmpty() : "unnamed package cannot be in named module";
            if (!targetModule.isOpen(pn, callerModule))
                throw new IllegalAccessException(targetModule + " does not open " + pn + " to " + callerModule);
        }
--- a/src/java.base/share/classes/java/lang/invoke/ProxyClassesDumper.java
+++ b/src/java.base/share/classes/java/lang/invoke/ProxyClassesDumper.java
@ -62,7 +62,7 @@ final class ProxyClassesDumper {
        }
        try {
            path = path.trim();
-            final Path dir = Path.of(path.length() == 0 ? "." : path);
+            final Path dir = Path.of(path.isEmpty() ? "." : path);
            AccessController.doPrivileged(new PrivilegedAction<>() {
                    @Override
                    public Void run() {
--- a/src/java.base/share/classes/java/lang/invoke/TypeDescriptor.java
+++ b/src/java.base/share/classes/java/lang/invoke/TypeDescriptor.java
@ -61,7 +61,8 @@ public interface TypeDescriptor {
        boolean isArray();

        /**
-         * Does this field descriptor describe a primitive type?
+         * Does this field descriptor describe a primitive type (including void.)
+         *
         * @return whether this field descriptor describes a primitive type
         */
        boolean isPrimitive();
--- a/src/java.base/share/classes/java/lang/invoke/VarHandle.java
+++ b/src/java.base/share/classes/java/lang/invoke/VarHandle.java
@ -1864,6 +1864,16 @@ public abstract class VarHandle implements Constable {
        }
    }

+    /**
+     * Compare this {@linkplain VarHandle} with another object for equality.
+     * Two {@linkplain VarHandle}s are considered equal if they both describe the
+     * same instance field, both describe the same static field, both describe
+     * array elements for arrays with the same component type, or both describe
+     * the same component of an off-heap structure.
+     *
+     * @param o the other object
+     * @return Whether this {@linkplain VarHandle} is equal to the other object
+     */
    @Override
    public final boolean equals(Object o) {
        if (this == o) return true;
@ -1883,6 +1893,12 @@ public abstract class VarHandle implements Constable {

    abstract int internalHashCode();

+    /**
+     * Returns a compact textual description of this {@linkplain VarHandle},
+     * including the type of variable described, and a description of its coordinates.
+     *
+     * @return A compact textual description of this {@linkplain VarHandle}
+     */
    @Override
    public final String toString() {
        return String.format("VarHandle[varType=%s, coord=%s]",
@ -2272,6 +2288,14 @@ public abstract class VarHandle implements Constable {
            }
        }

+        /**
+         * Returns a compact textual description of this constant description.
+         * For a field {@linkplain VarHandle}, includes the owner, name, and type
+         * of the field, and whether it is static; for an array {@linkplain VarHandle},
+         * the name of the component type.
+         *
+         * @return A compact textual description of this descriptor
+         */
        @Override
        public String toString() {
            switch (kind) {
--- a/src/java.base/share/classes/java/net/HttpCookie.java
+++ b/src/java.base/share/classes/java/net/HttpCookie.java
@ -149,7 +149,7 @@ public final class HttpCookie implements Cloneable {
     */
    HttpCookie(String name, String value, String header, long creationTime) {
        name = name.trim();
-        if (name.length() == 0 || !isToken(name) || name.charAt(0) == '$') {
+        if (name.isEmpty() || !isToken(name) || name.charAt(0) == '$') {
            throw new IllegalArgumentException("Illegal cookie name");
        }

--- a/src/java.base/share/classes/java/net/Inet6Address.java
+++ b/src/java.base/share/classes/java/net/Inet6Address.java
@ -433,7 +433,7 @@ class Inet6Address extends InetAddress {
                                            NetworkInterface nif)
        throws UnknownHostException
    {
-        if (host != null && host.length() > 0 && host.charAt(0) == '[') {
+        if (host != null && !host.isEmpty() && host.charAt(0) == '[') {
            if (host.charAt(host.length()-1) == ']') {
                host = host.substring(1, host.length() -1);
            }
@ -466,7 +466,7 @@ class Inet6Address extends InetAddress {
                                            int scope_id)
        throws UnknownHostException
    {
-        if (host != null && host.length() > 0 && host.charAt(0) == '[') {
+        if (host != null && !host.isEmpty() && host.charAt(0) == '[') {
            if (host.charAt(host.length()-1) == ']') {
                host = host.substring(1, host.length() -1);
            }
@ -601,7 +601,7 @@ class Inet6Address extends InetAddress {
        boolean scope_ifname_set = gf.get("scope_ifname_set", false);
        String ifname = (String)gf.get("ifname", null);

-        if (ifname != null && !"".equals (ifname)) {
+        if (ifname != null && !ifname.isEmpty()) {
            try {
                scope_ifname = NetworkInterface.getByName(ifname);
                if (scope_ifname == null) {
--- a/src/java.base/share/classes/java/net/InetAddress.java
+++ b/src/java.base/share/classes/java/net/InetAddress.java
@ -1187,7 +1187,7 @@ class InetAddress implements java.io.Serializable {
     */
    public static InetAddress getByAddress(String host, byte[] addr)
        throws UnknownHostException {
-        if (host != null && host.length() > 0 && host.charAt(0) == '[') {
+        if (host != null && !host.isEmpty() && host.charAt(0) == '[') {
            if (host.charAt(host.length()-1) == ']') {
                host = host.substring(1, host.length() -1);
            }
@ -1301,7 +1301,7 @@ class InetAddress implements java.io.Serializable {
    private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
        throws UnknownHostException {

-        if (host == null || host.length() == 0) {
+        if (host == null || host.isEmpty()) {
            InetAddress[] ret = new InetAddress[1];
            ret[0] = impl.loopbackAddress();
            return ret;
--- a/src/java.base/share/classes/java/net/SocketPermission.java
+++ b/src/java.base/share/classes/java/net/SocketPermission.java
@ -460,7 +460,7 @@ public final class SocketPermission extends Permission
            }
            return;
        } else {
-            if (host.length() > 0) {
+            if (!host.isEmpty()) {
                // see if we are being initialized with an IP address.
                char ch = host.charAt(0);
                if (ch == ':' || Character.digit(ch, 16) != -1) {
@ -705,8 +705,7 @@ public final class SocketPermission extends Permission
                                      .orElse(b);
        }

-        return cdomain.length() != 0 && hdomain.length() != 0
-                        && cdomain.equals(hdomain);
+        return !cdomain.isEmpty() && !hdomain.isEmpty() && cdomain.equals(hdomain);
    }

    private boolean authorized(String cname, byte[] addr) {
--- a/src/java.base/share/classes/java/net/URI.java
+++ b/src/java.base/share/classes/java/net/URI.java
@ -1959,10 +1959,8 @@ public final class URI
        throws URISyntaxException
    {
        if (scheme != null) {
-            if ((path != null)
-                && ((path.length() > 0) && (path.charAt(0) != '/')))
-                throw new URISyntaxException(s,
-                                             "Relative path in absolute URI");
+            if (path != null && !path.isEmpty() && path.charAt(0) != '/')
+                throw new URISyntaxException(s, "Relative path in absolute URI");
        }
    }

@ -2163,7 +2161,7 @@ public final class URI
            ru.port = base.port;

            String cp = (child.path == null) ? "" : child.path;
-            if ((cp.length() > 0) && (cp.charAt(0) == '/')) {
+            if (!cp.isEmpty() && cp.charAt(0) == '/') {
                // 5.2 (5): Child path is absolute
                ru.path = child.path;
            } else {
@ -2187,7 +2185,7 @@ public final class URI
    // o.w., return a new URI containing the normalized path.
    //
    private static URI normalize(URI u) {
-        if (u.isOpaque() || (u.path == null) || (u.path.length() == 0))
+        if (u.isOpaque() || u.path == null || u.path.isEmpty())
            return u;

        String np = normalize(u.path);
--- a/src/java.base/share/classes/java/net/URL.java
+++ b/src/java.base/share/classes/java/net/URL.java
@ -1513,7 +1513,7 @@ public final class URL implements java.io.Serializable {
        String ref = (String)gf.get("ref", null);
        int hashCode = gf.get("hashCode", -1);
        if (authority == null
-                && ((host != null && host.length() > 0) || port != -1)) {
+                && ((host != null && !host.isEmpty()) || port != -1)) {
            if (host == null)
                host = "";
            authority = (port == -1) ? host : host + ":" + port;
@ -1560,7 +1560,7 @@ public final class URL implements java.io.Serializable {

        // Construct authority part
        if (authority == null
-            && ((host != null && host.length() > 0) || port != -1)) {
+            && ((host != null && !host.isEmpty()) || port != -1)) {
            if (host == null)
                host = "";
            authority = (port == -1) ? host : host + ":" + port;
@ -1716,7 +1716,7 @@ final class UrlDeserializedState {

        // pre-compute length of StringBuffer
        int len = protocol.length() + 1;
-        if (authority != null && authority.length() > 0)
+        if (authority != null && !authority.isEmpty())
            len += 2 + authority.length();
        if (file != null) {
            len += file.length();
@ -1726,7 +1726,7 @@ final class UrlDeserializedState {
        StringBuilder result = new StringBuilder(len);
        result.append(protocol);
        result.append(":");
-        if (authority != null && authority.length() > 0) {
+        if (authority != null && !authority.isEmpty()) {
            result.append("//");
            result.append(authority);
        }
--- a/src/java.base/share/classes/java/net/URLClassLoader.java
+++ b/src/java.base/share/classes/java/net/URLClassLoader.java
@ -743,7 +743,7 @@ public class URLClassLoader extends SecureClassLoader implements Closeable {
                locUrl = ((JarURLConnection)urlConnection).getJarFileURL();
            }
            String host = locUrl.getHost();
-            if (host != null && (host.length() > 0))
+            if (host != null && !host.isEmpty())
                p = new SocketPermission(host,
                                         SecurityConstants.SOCKET_CONNECT_ACCEPT_ACTION);
        }
--- a/src/java.base/share/classes/java/net/URLDecoder.java
+++ b/src/java.base/share/classes/java/net/URLDecoder.java
@ -133,7 +133,7 @@ public class URLDecoder {
     * @since 1.4
     */
    public static String decode(String s, String enc) throws UnsupportedEncodingException {
-        if (enc.length() == 0) {
+        if (enc.isEmpty()) {
            throw new UnsupportedEncodingException ("URLDecoder: empty string enc parameter");
        }

--- a/src/java.base/share/classes/java/net/URLPermission.java
+++ b/src/java.base/share/classes/java/net/URLPermission.java
@ -409,7 +409,7 @@ public final class URLPermission extends Permission {
            char c = methods.charAt(i);
            if (c == ',') {
                String s = b.toString();
-                if (s.length() > 0)
+                if (!s.isEmpty())
                    l.add(s);
                b = new StringBuilder();
            } else if (c == ' ' || c == '\t') {
@ -423,7 +423,7 @@ public final class URLPermission extends Permission {
            }
        }
        String s = b.toString();
-        if (s.length() > 0)
+        if (!s.isEmpty())
            l.add(s);
        return l;
    }
@ -448,7 +448,7 @@ public final class URLPermission extends Permission {
                b.append(c);
            } else if (c == ',') {
                String s = b.toString();
-                if (s.length() > 0)
+                if (!s.isEmpty())
                    l.add(s);
                b = new StringBuilder();
                capitalizeNext = true;
@ -458,7 +458,7 @@ public final class URLPermission extends Permission {
            }
        }
        String s = b.toString();
-        if (s.length() > 0)
+        if (!s.isEmpty())
            l.add(s);
        return l;
    }
--- a/src/java.base/share/classes/java/net/URLStreamHandler.java
+++ b/src/java.base/share/classes/java/net/URLStreamHandler.java
@ -235,7 +235,7 @@ public abstract class URLStreamHandler {
            start = i;
            // If the authority is defined then the path is defined by the
            // spec only; See RFC 2396 Section 5.2.4.
-            if (authority != null && authority.length() > 0)
+            if (authority != null && !authority.isEmpty())
                path = "";
        }

@ -247,7 +247,7 @@ public abstract class URLStreamHandler {
        if (start < limit) {
            if (spec.charAt(start) == '/') {
                path = spec.substring(start, limit);
-            } else if (path != null && path.length() > 0) {
+            } else if (path != null && !path.isEmpty()) {
                isRelPath = true;
                int ind = path.lastIndexOf('/');
                String separator = "";
@ -483,11 +483,11 @@ public abstract class URLStreamHandler {
        String s;
        return u.getProtocol()
            + ':'
-            + (((s = u.getAuthority()) != null && s.length() > 0)
+            + ((s = u.getAuthority()) != null && !s.isEmpty()
               ? "//" + s : "")
-            + (((s = u.getPath()) != null) ? s : "")
-            + (((s = u.getQuery()) != null) ? '?' + s : "")
-            + (((s = u.getRef()) != null) ? '#' + s : "");
+            + ((s = u.getPath()) != null ? s : "")
+            + ((s = u.getQuery()) != null ? '?' + s : "")
+            + ((s = u.getRef()) != null ? '#' + s : "");
    }

    /**
@ -544,7 +544,7 @@ public abstract class URLStreamHandler {
         */
        String authority = null;
        String userInfo = null;
-        if (host != null && host.length() != 0) {
+        if (host != null && !host.isEmpty()) {
            authority = (port == -1) ? host : host + ":" + port;
            int at = host.lastIndexOf('@');
            if (at != -1) {
--- a/src/java.base/share/classes/java/nio/file/LinkPermission.java
+++ b/src/java.base/share/classes/java/nio/file/LinkPermission.java
@ -104,7 +104,7 @@ public final class LinkPermission extends BasicPermission {
    public LinkPermission(String name, String actions) {
        super(name);
        checkName(name);
-        if (actions != null && actions.length() > 0) {
+        if (actions != null && !actions.isEmpty()) {
            throw new IllegalArgumentException("actions: " + actions);
        }
    }
--- a/src/java.base/share/classes/java/security/AlgorithmParameterGenerator.java
+++ b/src/java.base/share/classes/java/security/AlgorithmParameterGenerator.java
@ -228,7 +228,7 @@ public class AlgorithmParameterGenerator {
        throws NoSuchAlgorithmException, NoSuchProviderException
    {
        Objects.requireNonNull(algorithm, "null algorithm name");
-        if (provider == null || provider.length() == 0)
+        if (provider == null || provider.isEmpty())
            throw new IllegalArgumentException("missing provider");
        Object[] objs = Security.getImpl(algorithm,
                                         "AlgorithmParameterGenerator",
--- a/src/java.base/share/classes/java/security/AlgorithmParameters.java
+++ b/src/java.base/share/classes/java/security/AlgorithmParameters.java
@ -209,7 +209,7 @@ public class AlgorithmParameters {
        throws NoSuchAlgorithmException, NoSuchProviderException
    {
        Objects.requireNonNull(algorithm, "null algorithm name");
-        if (provider == null || provider.length() == 0)
+        if (provider == null || provider.isEmpty())
            throw new IllegalArgumentException("missing provider");
        Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",
                                         provider);
--- a/src/java.base/share/classes/java/security/KeyStore.java
+++ b/src/java.base/share/classes/java/security/KeyStore.java
@ -913,7 +913,7 @@ public class KeyStore {
        throws KeyStoreException, NoSuchProviderException
    {
        Objects.requireNonNull(type, "null type name");
-        if (provider == null || provider.length() == 0)
+        if (provider == null || provider.isEmpty())
            throw new IllegalArgumentException("missing provider");
        try {
            Object[] objs = Security.getImpl(type, "KeyStore", provider);
--- a/src/java.base/share/classes/java/security/MessageDigest.java
+++ b/src/java.base/share/classes/java/security/MessageDigest.java
@ -237,7 +237,7 @@ public abstract class MessageDigest extends MessageDigestSpi {
        throws NoSuchAlgorithmException, NoSuchProviderException
    {
        Objects.requireNonNull(algorithm, "null algorithm name");
-        if (provider == null || provider.length() == 0)
+        if (provider == null || provider.isEmpty())
            throw new IllegalArgumentException("missing provider");
        Object[] objs = Security.getImpl(algorithm, "MessageDigest", provider);
        if (objs[0] instanceof MessageDigest) {
--- a/src/java.base/share/classes/java/security/Permission.java
+++ b/src/java.base/share/classes/java/security/Permission.java
@ -222,7 +222,7 @@ public abstract class Permission implements Guard, java.io.Serializable {
     */
    public String toString() {
        String actions = getActions();
-        if ((actions == null) || (actions.length() == 0)) { // OPTIONAL
+        if (actions == null || actions.isEmpty()) { // OPTIONAL
            return "(\"" + getClass().getName() + "\" \"" + name + "\")";
        } else {
            return "(\"" + getClass().getName() + "\" \"" + name +
--- a/src/java.base/share/classes/java/security/Policy.java
+++ b/src/java.base/share/classes/java/security/Policy.java
@ -456,7 +456,7 @@ public abstract class Policy {
                throws NoSuchProviderException, NoSuchAlgorithmException {

        Objects.requireNonNull(type, "null type name");
-        if (provider == null || provider.length() == 0) {
+        if (provider == null || provider.isEmpty()) {
            throw new IllegalArgumentException("missing provider");
        }

--- a/src/java.base/share/classes/java/security/SecureRandom.java
+++ b/src/java.base/share/classes/java/security/SecureRandom.java
@ -942,7 +942,7 @@ public class SecureRandom extends java.util.Random {
                }
            });

-        if ((property == null) || (property.length() == 0)) {
+        if (property == null || property.isEmpty()) {
            throw new NoSuchAlgorithmException(
                "Null/empty securerandom.strongAlgorithms Security Property");
        }
--- a/src/java.base/share/classes/java/security/Security.java
+++ b/src/java.base/share/classes/java/security/Security.java
@ -649,7 +649,7 @@ public final class Security {
            }
        }

-        if ((candidates == null) || (candidates.isEmpty()))
+        if (candidates == null || candidates.isEmpty())
            return null;

        Object[] candidatesArray = candidates.toArray();
@ -1005,11 +1005,11 @@ public final class Security {
        String algName = null;
        String attrName = null;

-        if (filterValue.length() == 0) {
+        if (filterValue.isEmpty()) {
            // The filterValue is an empty string. So the filterKey
            // should be in the format of <crypto_service>.<algorithm_or_type>.
            algName = filterKey.substring(algIndex + 1).trim();
-            if (algName.length() == 0) {
+            if (algName.isEmpty()) {
                // There must be a algorithm or type name.
                throw new InvalidParameterException("Invalid filter");
            }
@ -1024,7 +1024,7 @@ public final class Security {
                throw new InvalidParameterException("Invalid filter");
            } else {
                attrName = filterKey.substring(attrIndex + 1).trim();
-                if (attrName.length() == 0) {
+                if (attrName.isEmpty()) {
                    // There is no attribute name in the filter.
                    throw new InvalidParameterException("Invalid filter");
                }
@ -1070,7 +1070,7 @@ public final class Security {
     **/
    public static Set<String> getAlgorithms(String serviceName) {

-        if ((serviceName == null) || (serviceName.length() == 0) ||
+        if ((serviceName == null) || (serviceName.isEmpty()) ||
            (serviceName.endsWith("."))) {
            return Collections.emptySet();
        }
--- a/src/java.base/share/classes/java/security/Signature.java
+++ b/src/java.base/share/classes/java/security/Signature.java
@ -360,7 +360,7 @@ public abstract class Signature extends SignatureSpi {
        Objects.requireNonNull(algorithm, "null algorithm name");
        if (algorithm.equalsIgnoreCase(RSA_SIGNATURE)) {
            // exception compatibility with existing code
-            if ((provider == null) || (provider.length() == 0)) {
+            if (provider == null || provider.isEmpty()) {
                throw new IllegalArgumentException("missing provider");
            }
            Provider p = Security.getProvider(provider);
--- a/src/java.base/share/classes/java/security/cert/TrustAnchor.java
+++ b/src/java.base/share/classes/java/security/cert/TrustAnchor.java
@ -210,7 +210,7 @@ public class TrustAnchor {
        if (caName == null)
            throw new NullPointerException("the caName parameter must be " +
                "non-null");
-        if (caName.length() == 0)
+        if (caName.isEmpty())
            throw new IllegalArgumentException("the caName " +
                "parameter must be a non-empty String");
        // check if caName is formatted correctly
--- a/src/java.base/share/classes/java/text/AttributedString.java
+++ b/src/java.base/share/classes/java/text/AttributedString.java
@ -85,7 +85,7 @@ public class AttributedString {

            text = buffer.toString();

-            if (text.length() > 0) {
+            if (!text.isEmpty()) {
                // Determine the runs, creating a new run when the attributes
                // differ.
                int offset = 0;
@ -144,7 +144,7 @@ public class AttributedString {
        }
        this.text = text;

-        if (text.length() == 0) {
+        if (text.isEmpty()) {
            if (attributes.isEmpty())
                return;
            throw new IllegalArgumentException("Can't add attribute to 0-length text");
--- a/src/java.base/share/classes/java/text/CollationElementIterator.java
+++ b/src/java.base/share/classes/java/text/CollationElementIterator.java
@ -125,7 +125,7 @@ public final class CollationElementIterator
    CollationElementIterator(String sourceText, RuleBasedCollator owner) {
        this.owner = owner;
        ordering = owner.getTables();
-        if ( sourceText.length() != 0 ) {
+        if (!sourceText.isEmpty()) {
            NormalizerBase.Mode mode =
                CollatorUtilities.toNormalizerMode(owner.getDecomposition());
            text = new NormalizerBase(sourceText, mode);
--- a/src/java.base/share/classes/java/text/CompactNumberFormat.java
+++ b/src/java.base/share/classes/java/text/CompactNumberFormat.java
@ -799,7 +799,7 @@ public final class CompactNumberFormat extends NumberFormat {
     */
    private void append(StringBuffer result, String string,
            FieldDelegate delegate, List<FieldPosition> positions) {
-        if (string.length() > 0) {
+        if (!string.isEmpty()) {
            int start = result.length();
            result.append(string);
            for (int counter = 0; counter < positions.size(); counter++) {
@ -1213,7 +1213,7 @@ public final class CompactNumberFormat extends NumberFormat {
        }

        // If no 0s are specified in a non empty pattern, it is invalid
-        if (pattern.length() != 0 && zeros.isEmpty()) {
+        if (!pattern.isEmpty() && zeros.isEmpty()) {
            throw new IllegalArgumentException("Invalid pattern"
                    + " [" + pattern + "]: all patterns must include digit"
                    + " placement 0s");
--- a/src/java.base/share/classes/java/text/DecimalFormat.java
+++ b/src/java.base/share/classes/java/text/DecimalFormat.java
@ -1113,11 +1113,9 @@ public class DecimalFormat extends NumberFormat {

            // Records the need for adding prefix or suffix
            fastPathData.positiveAffixesRequired
-                    = (positivePrefix.length() != 0)
-                        || (positiveSuffix.length() != 0);
+                    = !positivePrefix.isEmpty() || !positiveSuffix.isEmpty();
            fastPathData.negativeAffixesRequired
-                    = (negativePrefix.length() != 0)
-                        || (negativeSuffix.length() != 0);
+                    = !negativePrefix.isEmpty() || !negativeSuffix.isEmpty();

            // Creates a cached char container for result, with max possible size.
            int maxNbIntegralDigits = 10;
@ -2062,7 +2060,7 @@ public class DecimalFormat extends NumberFormat {
                        Format.Field signAttribute) {
        int start = result.length();

-        if (string.length() > 0) {
+        if (!string.isEmpty()) {
            result.append(string);
            for (int counter = 0, max = positions.length; counter < max;
                 counter++) {
@ -3042,7 +3040,7 @@ public class DecimalFormat extends NumberFormat {
                    } else {
                        string = symbols.getCurrencySymbol();
                    }
-                    if (string.length() > 0) {
+                    if (!string.isEmpty()) {
                        if (positions == null) {
                            positions = new ArrayList<>(2);
                        }
@ -3613,7 +3611,7 @@ public class DecimalFormat extends NumberFormat {
            }
        }

-        if (pattern.length() == 0) {
+        if (pattern.isEmpty()) {
            posPrefixPattern = posSuffixPattern = "";
            setMinimumIntegerDigits(0);
            setMaximumIntegerDigits(MAXIMUM_INTEGER_DIGITS);
--- a/src/java.base/share/classes/java/text/DecimalFormatSymbols.java
+++ b/src/java.base/share/classes/java/text/DecimalFormatSymbols.java
@ -663,7 +663,7 @@ public class DecimalFormatSymbols implements Cloneable, Serializable {
        // Check for empty country string separately because it's a valid
        // country ID for Locale (and used for the C locale), but not a valid
        // ISO 3166 country code, and exceptions are expensive.
-        if (locale.getCountry().length() > 0) {
+        if (!locale.getCountry().isEmpty()) {
            try {
                currency = Currency.getInstance(locale);
            } catch (IllegalArgumentException e) {
--- a/src/java.base/share/classes/java/text/MergeCollation.java
+++ b/src/java.base/share/classes/java/text/MergeCollation.java
@ -92,7 +92,7 @@ final class MergeCollation {
        int i;
        for (i = 0; i < patterns.size(); ++i) {
            PatternEntry entry = patterns.get(i);
-            if (entry.extension.length() != 0) {
+            if (!entry.extension.isEmpty()) {
                if (extList == null)
                    extList = new ArrayList<>();
                extList.add(entry);
@ -122,7 +122,7 @@ final class MergeCollation {
    private final PatternEntry findLastWithNoExtension(int i) {
        for (--i;i >= 0; --i) {
            PatternEntry entry = patterns.get(i);
-            if (entry.extension.length() == 0) {
+            if (entry.extension.isEmpty()) {
                return entry;
            }
        }
--- a/src/java.base/share/classes/java/text/MessageFormat.java
+++ b/src/java.base/share/classes/java/text/MessageFormat.java
@ -1330,7 +1330,7 @@ public class MessageFormat extends Format {
                        }
                        arg = null;
                    }
-                    if (arg != null && arg.length() > 0) {
+                    if (arg != null && !arg.isEmpty()) {
                        result.append(arg);
                        characterIterators.add(
                                 createAttributedCharacterIterator(
@ -1476,7 +1476,7 @@ public class MessageFormat extends Format {

        // now get the format
        Format newFormat = null;
-        if (segments[SEG_TYPE].length() != 0) {
+        if (!segments[SEG_TYPE].isEmpty()) {
            int type = findKeyword(segments[SEG_TYPE], TYPE_KEYWORDS);
            switch (type) {
            case TYPE_NULL:
--- a/src/java.base/share/classes/java/text/PatternEntry.java
+++ b/src/java.base/share/classes/java/text/PatternEntry.java
@ -141,7 +141,7 @@ class PatternEntry {
        if (showWhiteSpace)
            toAddTo.append(' ');
        appendQuoted(chars,toAddTo);
-        if (showExtension && extension.length() != 0) {
+        if (showExtension && !extension.isEmpty()) {
            toAddTo.append('/');
            appendQuoted(extension,toAddTo);
        }
--- a/src/java.base/share/classes/java/text/RBTableBuilder.java
+++ b/src/java.base/share/classes/java/text/RBTableBuilder.java
@ -75,13 +75,10 @@ final class RBTableBuilder {
     * @exception ParseException If the rules format is incorrect.
     */

-    public void build(String pattern, int decmp) throws ParseException
-    {
-        boolean isSource = true;
-        int i = 0;
+    public void build(String pattern, int decmp) throws ParseException {
        String expChars;
        String groupChars;
-        if (pattern.length() == 0)
+        if (pattern.isEmpty())
            throw new ParseException("Build rules empty.", 0);

        // This array maps Unicode characters to their collation ordering
@ -119,8 +116,7 @@ final class RBTableBuilder {
        int order = 0;

        // Now walk though each entry and add it to my own tables
-        for (i = 0; i < mPattern.getCount(); ++i)
-        {
+        for (int i = 0; i < mPattern.getCount(); ++i) {
            PatternEntry entry = mPattern.getItemAt(i);
            if (entry != null) {
                groupChars = entry.getChars();
@ -140,7 +136,7 @@ final class RBTableBuilder {
                order = increment(entry.getStrength(), order);
                expChars = entry.getExtension();

-                if (expChars.length() != 0) {
+                if (!expChars.isEmpty()) {
                    addExpandOrder(groupChars, expChars, order);
                } else if (groupChars.length() > 1) {
                    char ch = groupChars.charAt(0);
--- a/src/java.base/share/classes/java/time/ZoneId.java
+++ b/src/java.base/share/classes/java/time/ZoneId.java
@ -372,7 +372,7 @@ public abstract class ZoneId implements Serializable {
    public static ZoneId ofOffset(String prefix, ZoneOffset offset) {
        Objects.requireNonNull(prefix, "prefix");
        Objects.requireNonNull(offset, "offset");
-        if (prefix.length() == 0) {
+        if (prefix.isEmpty()) {
            return offset;
        }

--- a/src/java.base/share/classes/java/time/format/DateTimeFormatterBuilder.java
+++ b/src/java.base/share/classes/java/time/format/DateTimeFormatterBuilder.java
@ -1439,7 +1439,7 @@ public final class DateTimeFormatterBuilder {
     */
    public DateTimeFormatterBuilder appendLiteral(String literal) {
        Objects.requireNonNull(literal, "literal");
-        if (literal.length() > 0) {
+        if (!literal.isEmpty()) {
            if (literal.length() == 1) {
                appendInternal(new CharLiteralPrinterParser(literal.charAt(0)));
            } else {
@ -1832,7 +1832,7 @@ public final class DateTimeFormatterBuilder {
                    throw new IllegalArgumentException("Pattern ends with an incomplete string literal: " + pattern);
                }
                String str = pattern.substring(start + 1, pos);
-                if (str.length() == 0) {
+                if (str.isEmpty()) {
                    appendLiteral('\'');
                } else {
                    appendLiteral(str.replace("''", "'"));
@ -4332,7 +4332,7 @@ public final class DateTimeFormatterBuilder {
            this.key = k;
            this.value = v;
            this.child = child;
-            if (k.length() == 0){
+            if (k.isEmpty()) {
                c0 = 0xffff;
            } else {
                c0 = key.charAt(0);
--- a/src/java.base/share/classes/java/util/Calendar.java
+++ b/src/java.base/share/classes/java/util/Calendar.java
@ -2232,7 +2232,7 @@ public abstract class Calendar implements Serializable, Cloneable, Comparable<Ca
        if (strings != null) {
            Map<String,Integer> names = new HashMap<>();
            for (int i = 0; i < strings.length; i++) {
-                if (strings[i].length() == 0) {
+                if (strings[i].isEmpty()) {
                    continue;
                }
                names.put(strings[i], i);
--- a/src/java.base/share/classes/java/util/Locale.java
+++ b/src/java.base/share/classes/java/util/Locale.java
@ -1396,11 +1396,11 @@ public final class Locale implements Cloneable, Serializable {
     */
    @Override
    public final String toString() {
-        boolean l = (baseLocale.getLanguage().length() != 0);
-        boolean s = (baseLocale.getScript().length() != 0);
-        boolean r = (baseLocale.getRegion().length() != 0);
-        boolean v = (baseLocale.getVariant().length() != 0);
-        boolean e = (localeExtensions != null && localeExtensions.getID().length() != 0);
+        boolean l = !baseLocale.getLanguage().isEmpty();
+        boolean s = !baseLocale.getScript().isEmpty();
+        boolean r = !baseLocale.getRegion().isEmpty();
+        boolean v = !baseLocale.getVariant().isEmpty();
+        boolean e = localeExtensions != null && !localeExtensions.getID().isEmpty();

        StringBuilder result = new StringBuilder(baseLocale.getLanguage());
        if (r || (l && (v || s || e))) {
@ -1504,18 +1504,18 @@ public final class Locale implements Cloneable, Serializable {
        StringBuilder buf = new StringBuilder();

        String subtag = tag.getLanguage();
-        if (subtag.length() > 0) {
+        if (!subtag.isEmpty()) {
            buf.append(LanguageTag.canonicalizeLanguage(subtag));
        }

        subtag = tag.getScript();
-        if (subtag.length() > 0) {
+        if (!subtag.isEmpty()) {
            buf.append(LanguageTag.SEP);
            buf.append(LanguageTag.canonicalizeScript(subtag));
        }

        subtag = tag.getRegion();
-        if (subtag.length() > 0) {
+        if (!subtag.isEmpty()) {
            buf.append(LanguageTag.SEP);
            buf.append(LanguageTag.canonicalizeRegion(subtag));
        }
@ -1534,7 +1534,7 @@ public final class Locale implements Cloneable, Serializable {
        }

        subtag = tag.getPrivateuse();
-        if (subtag.length() > 0) {
+        if (!subtag.isEmpty()) {
            if (buf.length() > 0) {
                buf.append(LanguageTag.SEP);
            }
@ -1684,7 +1684,7 @@ public final class Locale implements Cloneable, Serializable {
        bldr.setLanguageTag(tag);
        BaseLocale base = bldr.getBaseLocale();
        LocaleExtensions exts = bldr.getLocaleExtensions();
-        if (exts == null && base.getVariant().length() > 0) {
+        if (exts == null && !base.getVariant().isEmpty()) {
            exts = getCompatibilityExtensions(base.getLanguage(), base.getScript(),
                                              base.getRegion(), base.getVariant());
        }
@ -1917,7 +1917,7 @@ public final class Locale implements Cloneable, Serializable {
     * @exception NullPointerException if <code>inLocale</code> is <code>null</code>
     */
    public String getDisplayVariant(Locale inLocale) {
-        if (baseLocale.getVariant().length() == 0)
+        if (baseLocale.getVariant().isEmpty())
            return "";

        LocaleResources lr = LocaleProviderAdapter
@ -1998,14 +1998,14 @@ public final class Locale implements Cloneable, Serializable {
        // The display name consists of a main name, followed by qualifiers.
        // Typically, the format is "MainName (Qualifier, Qualifier)" but this
        // depends on what pattern is stored in the display locale.
-        String   mainName       = null;
-        String[] qualifierNames = null;
+        String   mainName;
+        String[] qualifierNames;

        // The main name is the language, or if there is no language, the script,
        // then if no script, the country. If there is no language/script/country
        // (an anomalous situation) then the display name is simply the variant's
        // display name.
-        if (languageName.length() == 0 && scriptName.length() == 0 && countryName.length() == 0) {
+        if (languageName.isEmpty() && scriptName.isEmpty() && countryName.isEmpty()) {
            if (variantNames.length == 0) {
                return "";
            } else {
@ -2013,13 +2013,13 @@ public final class Locale implements Cloneable, Serializable {
            }
        }
        ArrayList<String> names = new ArrayList<>(4);
-        if (languageName.length() != 0) {
+        if (!languageName.isEmpty()) {
            names.add(languageName);
        }
-        if (scriptName.length() != 0) {
+        if (!scriptName.isEmpty()) {
            names.add(scriptName);
        }
-        if (countryName.length() != 0) {
+        if (!countryName.isEmpty()) {
            names.add(countryName);
        }
        if (variantNames.length != 0) {
@ -2309,7 +2309,7 @@ public final class Locale implements Cloneable, Serializable {
        String variant = (String)fields.get("variant", "");
        String extStr = (String)fields.get("extensions", "");
        baseLocale = BaseLocale.getInstance(convertOldISOCodes(language), script, country, variant);
-        if (extStr.length() > 0) {
+        if (!extStr.isEmpty()) {
            try {
                InternalLocaleBuilder bldr = new InternalLocaleBuilder();
                bldr.setExtensions(extStr);
@ -2367,13 +2367,13 @@ public final class Locale implements Cloneable, Serializable {
        LocaleExtensions extensions = null;
        // Special cases for backward compatibility support
        if (LocaleUtils.caseIgnoreMatch(language, "ja")
-                && script.length() == 0
+                && script.isEmpty()
                && LocaleUtils.caseIgnoreMatch(country, "jp")
                && "JP".equals(variant)) {
            // ja_JP_JP -> u-ca-japanese (calendar = japanese)
            extensions = LocaleExtensions.CALENDAR_JAPANESE;
        } else if (LocaleUtils.caseIgnoreMatch(language, "th")
-                && script.length() == 0
+                && script.isEmpty()
                && LocaleUtils.caseIgnoreMatch(country, "th")
                && "TH".equals(variant)) {
            // th_TH_TH -> u-nu-thai (numbersystem = thai)
@ -2806,7 +2806,7 @@ public final class Locale implements Cloneable, Serializable {
        public Locale build() {
            BaseLocale baseloc = localeBuilder.getBaseLocale();
            LocaleExtensions extensions = localeBuilder.getLocaleExtensions();
-            if (extensions == null && baseloc.getVariant().length() > 0) {
+            if (extensions == null && !baseloc.getVariant().isEmpty()) {
                extensions = getCompatibilityExtensions(baseloc.getLanguage(), baseloc.getScript(),
                        baseloc.getRegion(), baseloc.getVariant());
            }
--- a/src/java.base/share/classes/java/util/ResourceBundle.java
+++ b/src/java.base/share/classes/java/util/ResourceBundle.java
@ -771,8 +771,8 @@ public abstract class ResourceBundle {
        @Override
        public String toString() {
            String l = locale.toString();
-            if (l.length() == 0) {
-                if (locale.getVariant().length() != 0) {
+            if (l.isEmpty()) {
+                if (!locale.getVariant().isEmpty()) {
                    l = "__" + locale.getVariant();
                } else {
                    l = "\"\"";
@ -2903,7 +2903,7 @@ public abstract class ResourceBundle {
                    List<Locale> bokmalList = new LinkedList<>();
                    for (Locale l : tmpList) {
                        bokmalList.add(l);
-                        if (l.getLanguage().length() == 0) {
+                        if (l.getLanguage().isEmpty()) {
                            break;
                        }
                        bokmalList.add(Locale.getInstance("no", l.getScript(), l.getCountry(),
@ -2921,7 +2921,7 @@ public abstract class ResourceBundle {
                }
                // Special handling for Chinese
                else if (language.equals("zh")) {
-                    if (script.length() == 0 && region.length() > 0) {
+                    if (script.isEmpty() && !region.isEmpty()) {
                        // Supply script for users who want to use zh_Hans/zh_Hant
                        // as bundle names (recommended for Java7+)
                        switch (region) {
@ -2944,7 +2944,7 @@ public abstract class ResourceBundle {
            private static List<Locale> getDefaultList(String language, String script, String region, String variant) {
                List<String> variants = null;

-                if (variant.length() > 0) {
+                if (!variant.isEmpty()) {
                    variants = new LinkedList<>();
                    int idx = variant.length();
                    while (idx != -1) {
@ -2960,14 +2960,14 @@ public abstract class ResourceBundle {
                        list.add(Locale.getInstance(language, script, region, v, null));
                    }
                }
-                if (region.length() > 0) {
+                if (!region.isEmpty()) {
                    list.add(Locale.getInstance(language, script, region, "", null));
                }
-                if (script.length() > 0) {
+                if (!script.isEmpty()) {
                    list.add(Locale.getInstance(language, script, "", "", null));
                    // Special handling for Chinese
                    if (language.equals("zh")) {
-                        if (region.length() == 0) {
+                        if (region.isEmpty()) {
                            // Supply region(country) for users who still package Chinese
                            // bundles using old convension.
                            switch (script) {
@ -2988,11 +2988,11 @@ public abstract class ResourceBundle {
                            list.add(Locale.getInstance(language, "", region, v, null));
                        }
                    }
-                    if (region.length() > 0) {
+                    if (!region.isEmpty()) {
                        list.add(Locale.getInstance(language, "", region, "", null));
                    }
                }
-                if (language.length() > 0) {
+                if (!language.isEmpty()) {
                    list.add(Locale.getInstance(language, "", "", "", null));
                }
                // Add root locale at the end
--- a/src/java.base/share/classes/java/util/Scanner.java
+++ b/src/java.base/share/classes/java/util/Scanner.java
@ -1297,16 +1297,16 @@ public final class Scanner implements Iterator<String>, Closeable {
        nanString = "\\Q" + dfs.getNaN() + "\\E";
        infinityString = "\\Q" + dfs.getInfinity() + "\\E";
        positivePrefix = df.getPositivePrefix();
-        if (positivePrefix.length() > 0)
+        if (!positivePrefix.isEmpty())
            positivePrefix = "\\Q" + positivePrefix + "\\E";
        negativePrefix = df.getNegativePrefix();
-        if (negativePrefix.length() > 0)
+        if (!negativePrefix.isEmpty())
            negativePrefix = "\\Q" + negativePrefix + "\\E";
        positiveSuffix = df.getPositiveSuffix();
-        if (positiveSuffix.length() > 0)
+        if (!positiveSuffix.isEmpty())
            positiveSuffix = "\\Q" + positiveSuffix + "\\E";
        negativeSuffix = df.getNegativeSuffix();
-        if (negativeSuffix.length() > 0)
+        if (!negativeSuffix.isEmpty())
            negativeSuffix = "\\Q" + negativeSuffix + "\\E";

        // Force rebuilding and recompilation of locale dependent
--- a/src/java.base/share/classes/java/util/regex/Pattern.java
+++ b/src/java.base/share/classes/java/util/regex/Pattern.java
@ -1390,7 +1390,7 @@ public final class Pattern
        localTCNCount = 0;

        // if length > 0, the Pattern is lazily compiled
-        if (pattern.length() == 0) {
+        if (pattern.isEmpty()) {
            root = new Start(lastAccept);
            matchRoot = lastAccept;
            compiled = true;
@ -1423,7 +1423,7 @@ public final class Pattern
        localCount = 0;
        localTCNCount = 0;

-        if (pattern.length() > 0) {
+        if (!pattern.isEmpty()) {
            compile();
        } else {
            root = new Start(lastAccept);
--- a/src/java.base/share/classes/javax/crypto/Cipher.java
+++ b/src/java.base/share/classes/javax/crypto/Cipher.java
@ -341,7 +341,7 @@ public class Cipher {
            throw new NoSuchAlgorithmException("Invalid transformation " +
                                           "format:" + transformation);
        }
-        if ((parts[0] == null) || (parts[0].length() == 0)) {
+        if ((parts[0] == null) || (parts[0].isEmpty())) {
            throw new NoSuchAlgorithmException("Invalid transformation:" +
                                   "algorithm not specified-"
                                   + transformation);
@ -445,10 +445,10 @@ public class Cipher {
        String alg = parts[0];
        String mode = parts[1];
        String pad = parts[2];
-        if ((mode != null) && (mode.length() == 0)) {
+        if ((mode != null) && (mode.isEmpty())) {
            mode = null;
        }
-        if ((pad != null) && (pad.length() == 0)) {
+        if ((pad != null) && (pad.isEmpty())) {
            pad = null;
        }

@ -634,7 +634,7 @@ public class Cipher {
        if ((transformation == null) || transformation.isEmpty()) {
            throw new NoSuchAlgorithmException("Null or empty transformation");
        }
-        if ((provider == null) || (provider.length() == 0)) {
+        if ((provider == null) || (provider.isEmpty())) {
            throw new IllegalArgumentException("Missing provider");
        }
        Provider p = Security.getProvider(provider);
--- a/src/java.base/share/classes/javax/crypto/SealedObject.java
+++ b/src/java.base/share/classes/javax/crypto/SealedObject.java
@ -337,7 +337,7 @@ public class SealedObject implements Serializable {
        if (key == null) {
            throw new NullPointerException("key is null");
        }
-        if (provider == null || provider.length() == 0) {
+        if (provider == null || provider.isEmpty()) {
            throw new IllegalArgumentException("missing provider");
        }

--- a/src/java.base/share/classes/javax/net/ssl/SSLSocketFactory.java
+++ b/src/java.base/share/classes/javax/net/ssl/SSLSocketFactory.java
@ -133,7 +133,7 @@ public abstract class SSLSocketFactory extends SocketFactory
                String s = java.security.Security.getProperty(name);
                if (s != null) {
                    s = s.trim();
-                    if (s.length() == 0) {
+                    if (s.isEmpty()) {
                        s = null;
                    }
                }
--- a/src/java.base/share/classes/javax/security/auth/PrivateCredentialPermission.java
+++ b/src/java.base/share/classes/javax/security/auth/PrivateCredentialPermission.java
@ -312,7 +312,7 @@ public final class PrivateCredentialPermission extends Permission {

    private void init(String name) {

-        if (name == null || name.trim().length() == 0) {
+        if (name == null || name.trim().isEmpty()) {
            throw new IllegalArgumentException("invalid empty name");
        }

--- a/src/java.base/share/classes/javax/security/auth/callback/ChoiceCallback.java
+++ b/src/java.base/share/classes/javax/security/auth/callback/ChoiceCallback.java
@ -98,13 +98,13 @@ public class ChoiceCallback implements Callback, java.io.Serializable {
    public ChoiceCallback(String prompt, String[] choices,
                int defaultChoice, boolean multipleSelectionsAllowed) {

-        if (prompt == null || prompt.length() == 0 ||
+        if (prompt == null || prompt.isEmpty() ||
            choices == null || choices.length == 0 ||
            defaultChoice < 0 || defaultChoice >= choices.length)
            throw new IllegalArgumentException();

        for (int i = 0; i < choices.length; i++) {
-            if (choices[i] == null || choices[i].length() == 0)
+            if (choices[i] == null || choices[i].isEmpty())
                throw new IllegalArgumentException();
        }

--- a/src/java.base/share/classes/javax/security/auth/callback/ConfirmationCallback.java
+++ b/src/java.base/share/classes/javax/security/auth/callback/ConfirmationCallback.java
@ -248,7 +248,7 @@ public class ConfirmationCallback implements Callback, java.io.Serializable {
            throw new IllegalArgumentException();

        for (int i = 0; i < options.length; i++) {
-            if (options[i] == null || options[i].length() == 0)
+            if (options[i] == null || options[i].isEmpty())
                throw new IllegalArgumentException();
        }

@ -294,7 +294,7 @@ public class ConfirmationCallback implements Callback, java.io.Serializable {
    public ConfirmationCallback(String prompt, int messageType,
                int optionType, int defaultOption) {

-        if (prompt == null || prompt.length() == 0 ||
+        if (prompt == null || prompt.isEmpty() ||
            messageType < INFORMATION || messageType > ERROR ||
            optionType < YES_NO_OPTION || optionType > OK_CANCEL_OPTION)
            throw new IllegalArgumentException();
@ -357,14 +357,14 @@ public class ConfirmationCallback implements Callback, java.io.Serializable {
    public ConfirmationCallback(String prompt, int messageType,
                String[] options, int defaultOption) {

-        if (prompt == null || prompt.length() == 0 ||
+        if (prompt == null || prompt.isEmpty() ||
            messageType < INFORMATION || messageType > ERROR ||
            options == null || options.length == 0 ||
            defaultOption < 0 || defaultOption >= options.length)
            throw new IllegalArgumentException();

        for (int i = 0; i < options.length; i++) {
-            if (options[i] == null || options[i].length() == 0)
+            if (options[i] == null || options[i].isEmpty())
                throw new IllegalArgumentException();
        }

--- a/src/java.base/share/classes/javax/security/auth/callback/NameCallback.java
+++ b/src/java.base/share/classes/javax/security/auth/callback/NameCallback.java
@ -62,7 +62,7 @@ public class NameCallback implements Callback, java.io.Serializable {
     *                  or if {@code prompt} has a length of 0.
     */
    public NameCallback(String prompt) {
-        if (prompt == null || prompt.length() == 0)
+        if (prompt == null || prompt.isEmpty())
            throw new IllegalArgumentException();
        this.prompt = prompt;
    }
@ -82,8 +82,8 @@ public class NameCallback implements Callback, java.io.Serializable {
     *                  or if {@code defaultName} has a length of 0.
     */
    public NameCallback(String prompt, String defaultName) {
-        if (prompt == null || prompt.length() == 0 ||
-            defaultName == null || defaultName.length() == 0)
+        if (prompt == null || prompt.isEmpty() ||
+            defaultName == null || defaultName.isEmpty())
            throw new IllegalArgumentException();

        this.prompt = prompt;
--- a/src/java.base/share/classes/javax/security/auth/callback/PasswordCallback.java
+++ b/src/java.base/share/classes/javax/security/auth/callback/PasswordCallback.java
@ -67,7 +67,7 @@ public class PasswordCallback implements Callback, java.io.Serializable {
     *                  if {@code prompt} has a length of 0.
     */
    public PasswordCallback(String prompt, boolean echoOn) {
-        if (prompt == null || prompt.length() == 0)
+        if (prompt == null || prompt.isEmpty())
            throw new IllegalArgumentException();

        this.prompt = prompt;
--- a/src/java.base/share/classes/javax/security/auth/callback/TextInputCallback.java
+++ b/src/java.base/share/classes/javax/security/auth/callback/TextInputCallback.java
@ -63,7 +63,7 @@ public class TextInputCallback implements Callback, java.io.Serializable {
     *                  or if {@code prompt} has a length of 0.
     */
    public TextInputCallback(String prompt) {
-        if (prompt == null || prompt.length() == 0)
+        if (prompt == null || prompt.isEmpty())
            throw new IllegalArgumentException();
        this.prompt = prompt;
    }
@ -83,8 +83,8 @@ public class TextInputCallback implements Callback, java.io.Serializable {
     *                  or if {@code defaultText} has a length of 0.
     */
    public TextInputCallback(String prompt, String defaultText) {
-        if (prompt == null || prompt.length() == 0 ||
-            defaultText == null || defaultText.length() == 0)
+        if (prompt == null || prompt.isEmpty() ||
+            defaultText == null || defaultText.isEmpty())
            throw new IllegalArgumentException();

        this.prompt = prompt;
--- a/src/java.base/share/classes/javax/security/auth/callback/TextOutputCallback.java
+++ b/src/java.base/share/classes/javax/security/auth/callback/TextOutputCallback.java
@ -74,7 +74,7 @@ public class TextOutputCallback implements Callback, java.io.Serializable {
    public TextOutputCallback(int messageType, String message) {
        if ((messageType != INFORMATION &&
                messageType != WARNING && messageType != ERROR) ||
-            message == null || message.length() == 0)
+            message == null || message.isEmpty())
            throw new IllegalArgumentException();

        this.messageType = messageType;
--- a/src/java.base/share/classes/javax/security/auth/login/AppConfigurationEntry.java
+++ b/src/java.base/share/classes/javax/security/auth/login/AppConfigurationEntry.java
@ -75,7 +75,7 @@ public class AppConfigurationEntry {
                                LoginModuleControlFlag controlFlag,
                                Map<String,?> options)
    {
-        if (loginModuleName == null || loginModuleName.length() == 0 ||
+        if (loginModuleName == null || loginModuleName.isEmpty() ||
            (controlFlag != LoginModuleControlFlag.REQUIRED &&
                controlFlag != LoginModuleControlFlag.REQUISITE &&
                controlFlag != LoginModuleControlFlag.SUFFICIENT &&
--- a/src/java.base/share/classes/javax/security/auth/login/Configuration.java
+++ b/src/java.base/share/classes/javax/security/auth/login/Configuration.java
@ -418,7 +418,7 @@ public abstract class Configuration {
                throws NoSuchProviderException, NoSuchAlgorithmException {

        Objects.requireNonNull(type, "null type name");
-        if (provider == null || provider.length() == 0) {
+        if (provider == null || provider.isEmpty()) {
            throw new IllegalArgumentException("missing provider");
        }

--- a/src/java.base/share/classes/javax/security/auth/login/LoginContext.java
+++ b/src/java.base/share/classes/javax/security/auth/login/LoginContext.java
@ -300,7 +300,7 @@ public class LoginContext {
                public CallbackHandler run() throws Exception {
                    String defaultHandler = java.security.Security.getProperty
                        (DEFAULT_HANDLER);
-                    if (defaultHandler == null || defaultHandler.length() == 0)
+                    if (defaultHandler == null || defaultHandler.isEmpty())
                        return null;
                    Class<? extends CallbackHandler> c = Class.forName(
                            defaultHandler, true,
--- a/src/java.base/share/classes/javax/security/cert/X509Certificate.java
+++ b/src/java.base/share/classes/javax/security/cert/X509Certificate.java
@ -210,7 +210,7 @@ public abstract class X509Certificate extends Certificate {
         * under JDK1.1.
         */
        String className = X509Provider;
-        if (className == null || className.length() == 0) {
+        if (className == null || className.isEmpty()) {
            // shouldn't happen, but assume corrupted properties file
            // provide access to sun implementation
            className = "com.sun.security.cert.internal.x509.X509V1CertImpl";
--- a/src/java.base/share/classes/jdk/internal/jimage/decompressor/SignatureParser.java
+++ b/src/java.base/share/classes/jdk/internal/jimage/decompressor/SignatureParser.java
@ -60,7 +60,7 @@ public class SignatureParser {
            switch (c) {
                case 'L': {
                    String pkg = arguments.get(arg_index);
-                    if(pkg.length() > 0) {
+                    if(!pkg.isEmpty()) {
                        out.append(pkg).append("/");
                    }
                    arg_index+=1;
--- a/src/java.base/share/classes/jdk/internal/jimage/decompressor/StringSharingDecompressor.java
+++ b/src/java.base/share/classes/jdk/internal/jimage/decompressor/StringSharingDecompressor.java
@ -168,7 +168,7 @@ public class StringSharingDecompressor implements ResourceDecompressor {
                int index = indices.get(argIndex);
                argIndex += 1;
                String pkg = reader.getString(index);
-                if (pkg.length() > 0) {
+                if (!pkg.isEmpty()) {
                    pkg = pkg + "/";
                    byte[] encoded = getEncoded(pkg);
                    buffer = safeAdd(buffer, encoded);
--- a/Show More
+++ b/Show More