8267452: Delegate forEachRemaining in Spliterators.iterator()

Reviewed-by: psandoz

src/java.base/share/classes/java/util/Spliterators.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -688,9 +688,23 @@ public final class Spliterators {
                     throw new NoSuchElementException();
                 else {
                     valueReady = false;
-                    return nextElement;
+                    T t = nextElement;
+                    nextElement = null;
+                    return t;
                 }
             }
+
+            @Override
+            public void forEachRemaining(Consumer<? super T> action) {
+                Objects.requireNonNull(action);
+                if (valueReady) {
+                    valueReady = false;
+                    T t = nextElement;
+                    nextElement = null;
+                    action.accept(t);
+                }
+                spliterator.forEachRemaining(action);
+            }
         }
 
         return new Adapter();
@@ -736,6 +750,16 @@ public final class Spliterators {
                     return nextElement;
                 }
             }
+
+            @Override
+            public void forEachRemaining(IntConsumer action) {
+                Objects.requireNonNull(action);
+                if (valueReady) {
+                    valueReady = false;
+                    action.accept(nextElement);
+                }
+                spliterator.forEachRemaining(action);
+            }
         }
 
         return new Adapter();
@@ -781,6 +805,16 @@ public final class Spliterators {
                     return nextElement;
                 }
             }
+
+            @Override
+            public void forEachRemaining(LongConsumer action) {
+                Objects.requireNonNull(action);
+                if (valueReady) {
+                    valueReady = false;
+                    action.accept(nextElement);
+                }
+                spliterator.forEachRemaining(action);
+            }
         }
 
         return new Adapter();
@@ -826,6 +860,16 @@ public final class Spliterators {
                     return nextElement;
                 }
             }
+
+            @Override
+            public void forEachRemaining(DoubleConsumer action) {
+                Objects.requireNonNull(action);
+                if (valueReady) {
+                    valueReady = false;
+                    action.accept(nextElement);
+                }
+                spliterator.forEachRemaining(action);
+            }
         }
 
         return new Adapter();
@@ -1843,7 +1887,7 @@ public final class Spliterators {
     static final class IntIteratorSpliterator implements Spliterator.OfInt {
         static final int BATCH_UNIT = IteratorSpliterator.BATCH_UNIT;
         static final int MAX_BATCH = IteratorSpliterator.MAX_BATCH;
-        private PrimitiveIterator.OfInt it;
+        private final PrimitiveIterator.OfInt it;
         private final int characteristics;
         private long est;             // size estimate
         private int batch;            // batch size for splits
@@ -1937,7 +1981,7 @@ public final class Spliterators {
     static final class LongIteratorSpliterator implements Spliterator.OfLong {
         static final int BATCH_UNIT = IteratorSpliterator.BATCH_UNIT;
         static final int MAX_BATCH = IteratorSpliterator.MAX_BATCH;
-        private PrimitiveIterator.OfLong it;
+        private final PrimitiveIterator.OfLong it;
         private final int characteristics;
         private long est;             // size estimate
         private int batch;            // batch size for splits
@@ -2031,7 +2075,7 @@ public final class Spliterators {
     static final class DoubleIteratorSpliterator implements Spliterator.OfDouble {
         static final int BATCH_UNIT = IteratorSpliterator.BATCH_UNIT;
         static final int MAX_BATCH = IteratorSpliterator.MAX_BATCH;
-        private PrimitiveIterator.OfDouble it;
+        private final PrimitiveIterator.OfDouble it;
         private final int characteristics;
         private long est;             // size estimate
         private int batch;            // batch size for splits

test/jdk/java/util/Spliterator/IteratorFromSpliteratorTest.java

@@ -0,0 +1,149 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import org.testng.annotations.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.PrimitiveIterator;
+import java.util.Spliterators;
+import java.util.function.DoubleConsumer;
+import java.util.function.IntConsumer;
+import java.util.function.LongConsumer;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertFalse;
+import static org.testng.Assert.assertThrows;
+import static org.testng.Assert.fail;
+
+/**
+ * @test
+ * @summary Spliterator.iterator traversing tests
+ * @library /lib/testlibrary/bootlib
+ * @run testng IteratorFromSpliteratorTest
+ * @bug 8267452
+ */
+public class IteratorFromSpliteratorTest {
+    @Test
+    public void testIteratorFromSpliterator() {
+        List<Integer> input = List.of(1, 2, 3, 4, 5);
+        for (int i = 0; i < input.size(); i++) {
+            Iterator<Integer> iterator = Spliterators.iterator(input.spliterator());
+            List<Integer> result = new ArrayList<>();
+            int j = i;
+            while (j++ < input.size() && iterator.hasNext()) {
+                result.add(iterator.next());
+            }
+            // While SpliteratorTraversingAndSplittingTest tests some scenarios with Spliterators.iterator
+            // it always wraps the resulting iterator into spliterator again, and this limits the use patterns.
+            // In particular, calling hasNext() right before forEachRemaining() is not tested.
+            // Here we cover such a scenario.
+            assertEquals(iterator.hasNext(), result.size() < input.size());
+            iterator.forEachRemaining(result::add);
+            iterator.forEachRemaining(x -> fail("Should not be called"));
+            assertFalse(iterator.hasNext());
+            assertThrows(NoSuchElementException.class, iterator::next);
+            iterator.forEachRemaining(x -> fail("Should not be called"));
+            assertEquals(result, input);
+        }
+    }
+
+    @Test
+    public void testIteratorFromSpliteratorInt() {
+        int[] input = {1, 2, 3, 4, 5};
+        for (int i = 0; i < input.length; i++) {
+            PrimitiveIterator.OfInt iterator = Spliterators.iterator(Arrays.spliterator(input));
+            List<Integer> result = new ArrayList<>();
+            int j = i;
+            while (j++ < input.length && iterator.hasNext()) {
+                result.add(iterator.nextInt());
+            }
+            assertEquals(iterator.hasNext(), result.size() < input.length);
+            iterator.forEachRemaining((IntConsumer) result::add);
+            iterator.forEachRemaining((IntConsumer) (x -> fail("Should not be called")));
+            assertFalse(iterator.hasNext());
+            assertThrows(NoSuchElementException.class, iterator::next);
+            iterator.forEachRemaining((IntConsumer) (x -> fail("Should not be called")));
+            assertEquals(result.stream().mapToInt(x -> x).toArray(), input);
+        }
+    }
+
+    @Test
+    public void testIteratorFromSpliteratorLong() {
+        long[] input = {1, 2, 3, 4, 5};
+        for (int i = 0; i < input.length; i++) {
+            PrimitiveIterator.OfLong iterator = Spliterators.iterator(Arrays.spliterator(input));
+            List<Long> result = new ArrayList<>();
+            int j = i;
+            while (j++ < input.length && iterator.hasNext()) {
+                result.add(iterator.nextLong());
+            }
+            assertEquals(iterator.hasNext(), result.size() < input.length);
+            iterator.forEachRemaining((LongConsumer) result::add);
+            iterator.forEachRemaining((LongConsumer) (x -> fail("Should not be called")));
+            assertFalse(iterator.hasNext());
+            assertThrows(NoSuchElementException.class, iterator::next);
+            iterator.forEachRemaining((LongConsumer) (x -> fail("Should not be called")));
+            assertEquals(result.stream().mapToLong(x -> x).toArray(), input);
+        }
+    }
+
+    @Test
+    public void testIteratorFromSpliteratorDouble() {
+        double[] input = {1, 2, 3, 4, 5};
+        for (int i = 0; i < input.length; i++) {
+            PrimitiveIterator.OfDouble iterator = Spliterators.iterator(Arrays.spliterator(input));
+            List<Double> result = new ArrayList<>();
+            int j = i;
+            while (j++ < input.length && iterator.hasNext()) {
+                result.add(iterator.nextDouble());
+            }
+            assertEquals(iterator.hasNext(), result.size() < input.length);
+            iterator.forEachRemaining((DoubleConsumer) result::add);
+            iterator.forEachRemaining((DoubleConsumer) (x -> fail("Should not be called")));
+            assertFalse(iterator.hasNext());
+            assertThrows(NoSuchElementException.class, iterator::next);
+            iterator.forEachRemaining((DoubleConsumer) (x -> fail("Should not be called")));
+            assertEquals(result.stream().mapToDouble(x -> x).toArray(), input);
+        }
+    }
+
+    @Test
+    public void testIteratorFromSpliteratorEmpty() {
+        Iterator<?>[] iterators = {
+            Spliterators.iterator(Spliterators.emptySpliterator()),
+            Spliterators.iterator(Spliterators.emptyIntSpliterator()),
+            Spliterators.iterator(Spliterators.emptyLongSpliterator()),
+            Spliterators.iterator(Spliterators.emptyDoubleSpliterator())
+        };
+        for (Iterator<?> iterator : iterators) {
+            iterator.forEachRemaining(x -> fail("Should not be called"));
+            assertFalse(iterator.hasNext());
+            iterator.forEachRemaining(x -> fail("Should not be called"));
+            assertThrows(NoSuchElementException.class, iterator::next);
+        }
+    }
+}