8016446: Improve forEach/replaceAll for Map, HashMap, Hashtable, IdentityHashMap, WeakHashMap, TreeMap, ConcurrentMap

Co-authored-by: Remi Forax <forax@univ-mlv.fr>
Reviewed-by: forax, mduigou, psandoz

jdk/src/share/classes/java/util/HashMap.java

@@ -29,6 +29,7 @@ import java.io.*;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.concurrent.ThreadLocalRandom;
+import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 import java.util.function.BiFunction;
 import java.util.function.Function;
@@ -1299,10 +1300,112 @@ public class HashMap<K,V>
      */
     public V remove(Object key) {
         Entry<K,V> e = removeEntryForKey(key);
-        return (e == null ? null : e.value);
+       return (e == null ? null : e.value);
+   }
+
+   // optimized implementations of default methods in Map
+
+    @Override
+    public void forEach(BiConsumer<? super K, ? super V> action) {
+        Objects.requireNonNull(action);
+        final int expectedModCount = modCount;
+        if (nullKeyEntry != null) {
+            forEachNullKey(expectedModCount, action);
+        }
+        Object[] tab = this.table;
+        for (int index = 0; index < tab.length; index++) {
+            Object item = tab[index];
+            if (item == null) {
+                continue;
+            }
+            if (item instanceof HashMap.TreeBin) {
+                eachTreeNode(expectedModCount, ((TreeBin)item).first, action);
+                continue;
+            }
+            @SuppressWarnings("unchecked")
+            Entry<K, V> entry = (Entry<K, V>)item;
+            while (entry != null) {
+                action.accept(entry.key, entry.value);
+                entry = (Entry<K, V>)entry.next;
+
+                if (expectedModCount != modCount) {
+                    throw new ConcurrentModificationException();
+                }
+            }
+        }
     }
 
-    // optimized implementations of default methods in Map
+    private void eachTreeNode(int expectedModCount, TreeNode<K, V> node, BiConsumer<? super K, ? super V> action) {
+        while (node != null) {
+            @SuppressWarnings("unchecked")
+            Entry<K, V> entry = (Entry<K, V>)node.entry;
+            action.accept(entry.key, entry.value);
+            node = (TreeNode<K, V>)entry.next;
+
+            if (expectedModCount != modCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
+    private void forEachNullKey(int expectedModCount, BiConsumer<? super K, ? super V> action) {
+        action.accept(null, nullKeyEntry.value);
+
+        if (expectedModCount != modCount) {
+            throw new ConcurrentModificationException();
+        }
+    }
+
+    @Override
+    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);
+        final int expectedModCount = modCount;
+        if (nullKeyEntry != null) {
+            replaceforNullKey(expectedModCount, function);
+        }
+        Object[] tab = this.table;
+        for (int index = 0; index < tab.length; index++) {
+            Object item = tab[index];
+            if (item == null) {
+                continue;
+            }
+            if (item instanceof HashMap.TreeBin) {
+                replaceEachTreeNode(expectedModCount, ((TreeBin)item).first, function);
+                continue;
+            }
+            @SuppressWarnings("unchecked")
+            Entry<K, V> entry = (Entry<K, V>)item;
+            while (entry != null) {
+                entry.value = function.apply(entry.key, entry.value);
+                entry = (Entry<K, V>)entry.next;
+
+                if (expectedModCount != modCount) {
+                    throw new ConcurrentModificationException();
+                }
+            }
+        }
+    }
+
+    private void replaceEachTreeNode(int expectedModCount, TreeNode<K, V> node, BiFunction<? super K, ? super V, ? extends V> function) {
+        while (node != null) {
+            @SuppressWarnings("unchecked")
+            Entry<K, V> entry = (Entry<K, V>)node.entry;
+            entry.value = function.apply(entry.key, entry.value);
+            node = (TreeNode<K, V>)entry.next;
+
+            if (expectedModCount != modCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
+    private void replaceforNullKey(int expectedModCount, BiFunction<? super K, ? super V, ? extends V> function) {
+        nullKeyEntry.value = function.apply(null, nullKeyEntry.value);
+
+        if (expectedModCount != modCount) {
+            throw new ConcurrentModificationException();
+        }
+    }
 
     @Override
     public V putIfAbsent(K key, V value) {
@@ -2297,12 +2400,12 @@ public class HashMap<K,V>
             if (e == null)
                 throw new NoSuchElementException();
 
-            if (e instanceof Entry) {
+            if (e instanceof TreeNode) { // TreeBin
-                retVal = (Entry<K,V>)e;
-                next = ((Entry<K,V>)e).next;
-            } else { // TreeBin
                 retVal = (Entry<K,V>)((TreeNode)e).entry;
                 next = retVal.next;
+            } else {
+                retVal = (Entry<K,V>)e;
+                next = ((Entry<K,V>)e).next;
             }
 
             if (next == null) { // Move to next bin

jdk/src/share/classes/java/util/Hashtable.java

@@ -932,19 +932,39 @@ public class Hashtable<K,V>
     public synchronized void forEach(BiConsumer<? super K, ? super V> action) {
         Objects.requireNonNull(action);     // explicit check required in case
                                             // table is empty.
-        Entry<?,?>[] tab = table;
+        final int expectedModCount = modCount;
-        for (Entry<?,?> entry : tab) {
+
+        Entry<?, ?>[] tab = table;
+        for (Entry<?, ?> entry : tab) {
             while (entry != null) {
                 action.accept((K)entry.key, (V)entry.value);
                 entry = entry.next;
+
+                if (expectedModCount != modCount) {
+                    throw new ConcurrentModificationException();
+                }
             }
         }
     }
 
     @Override
-    public synchronized void replaceAll(
+    public synchronized void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
-            BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);     // explicit check required in case
-        Map.super.replaceAll(function);
+                                              // table is empty.
+        final int expectedModCount = modCount;
+
+        Entry<K, V>[] tab = (Entry<K, V>[])table;
+        for (Entry<K, V> entry : tab) {
+            while (entry != null) {
+                entry.value = Objects.requireNonNull(
+                    function.apply(entry.key, entry.value));
+                entry = entry.next;
+
+                if (expectedModCount != modCount) {
+                    throw new ConcurrentModificationException();
+                }
+            }
+        }
     }
 
     @Override
@@ -1058,7 +1078,7 @@ public class Hashtable<K,V>
     }
 
     @Override
-    public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+    public synchronized V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
         Objects.requireNonNull(remappingFunction);
 
         Entry<?,?> tab[] = table;
@@ -1087,7 +1107,7 @@ public class Hashtable<K,V>
     }
 
     @Override
-    public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+    public synchronized V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
         Objects.requireNonNull(remappingFunction);
 
         Entry<?,?> tab[] = table;
@@ -1122,7 +1142,7 @@ public class Hashtable<K,V>
     }
 
     @Override
-    public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
+    public synchronized V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
         Objects.requireNonNull(remappingFunction);
 
         Entry<?,?> tab[] = table;

jdk/src/share/classes/java/util/IdentityHashMap.java

@@ -27,6 +27,8 @@ package java.util;
 
 import java.io.*;
 import java.lang.reflect.Array;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
 import java.util.function.Consumer;
 
 /**
@@ -1337,6 +1339,42 @@ public class IdentityHashMap<K,V>
         tab[i + 1] = value;
     }
 
+    @Override
+    public void forEach(BiConsumer<? super K, ? super V> action) {
+        Objects.requireNonNull(action);
+        int expectedModCount = modCount;
+
+        Object[] t = table;
+        for (int index = 0; index < t.length; index += 2) {
+            Object k = t[index];
+            if (k != null) {
+                action.accept((K) unmaskNull(k), (V) t[index + 1]);
+            }
+
+            if (modCount != expectedModCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
+    @Override
+    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);
+        int expectedModCount = modCount;
+
+        Object[] t = table;
+        for (int index = 0; index < t.length; index += 2) {
+            Object k = t[index];
+            if (k != null) {
+                t[index + 1] = function.apply((K) unmaskNull(k), (V) t[index + 1]);
+            }
+
+            if (modCount != expectedModCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
     /**
      * Similar form as array-based Spliterators, but skips blank elements,
      * and guestimates size as decreasing by half per split.

jdk/src/share/classes/java/util/LinkedHashMap.java

@@ -25,6 +25,8 @@
 
 package java.util;
 import java.io.*;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
 
 /**
  * <p>Hash table and linked list implementation of the <tt>Map</tt> interface,
@@ -296,6 +298,32 @@ public class LinkedHashMap<K,V>
         header.before = header.after = header;
     }
 
+    @Override
+    public void forEach(BiConsumer<? super K, ? super V> action) {
+        Objects.requireNonNull(action);
+        int expectedModCount = modCount;
+        for (Entry<K, V> entry = header.after; entry != header; entry = entry.after) {
+            action.accept(entry.key, entry.value);
+
+            if (expectedModCount != modCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
+    @Override
+    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);
+        int expectedModCount = modCount;
+        for (Entry<K, V> entry = header.after; entry != header; entry = entry.after) {
+            entry.value = function.apply(entry.key, entry.value);
+
+            if (expectedModCount != modCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
     /**
      * LinkedHashMap entry.
      */

jdk/src/share/classes/java/util/Map.java

@@ -545,6 +545,7 @@ public interface Map<K,V> {
                 k = entry.getKey();
                 v = entry.getValue();
             } catch(IllegalStateException ise) {
+                // this usually means the entry is no longer in the map.
                 throw new ConcurrentModificationException(ise);
             }
             action.accept(k, v);
@@ -599,9 +600,19 @@ public interface Map<K,V> {
                 k = entry.getKey();
                 v = entry.getValue();
             } catch(IllegalStateException ise) {
+                // this usually means the entry is no longer in the map.
+                throw new ConcurrentModificationException(ise);
+            }
+
+            // ise thrown from function is not a cme.
+            v = function.apply(k, v);
+
+            try {
+                entry.setValue(v);
+            } catch(IllegalStateException ise) {
+                // this usually means the entry is no longer in the map.
                 throw new ConcurrentModificationException(ise);
             }
-            entry.setValue(function.apply(k, v));
         }
     }
 

jdk/src/share/classes/java/util/TreeMap.java

@@ -25,6 +25,8 @@
 
 package java.util;
 
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
 import java.util.function.Consumer;
 
 /**
@@ -945,6 +947,33 @@ public class TreeMap<K,V>
         return tailMap(fromKey, true);
     }
 
+    @Override
+    public void forEach(BiConsumer<? super K, ? super V> action) {
+        Objects.requireNonNull(action);
+        int expectedModCount = modCount;
+        for (Entry<K, V> e = getFirstEntry(); e != null; e = successor(e)) {
+            action.accept(e.key, e.value);
+
+            if (expectedModCount != modCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
+    @Override
+    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);
+        int expectedModCount = modCount;
+
+        for (Entry<K, V> e = getFirstEntry(); e != null; e = successor(e)) {
+            e.value = Objects.requireNonNull(function.apply(e.key, e.value));
+
+            if (expectedModCount != modCount) {
+                throw new ConcurrentModificationException();
+            }
+        }
+    }
+
     // View class support
 
     class Values extends AbstractCollection<V> {

jdk/src/share/classes/java/util/WeakHashMap.java

@@ -28,6 +28,8 @@ package java.util;
 import java.lang.ref.WeakReference;
 import java.lang.ref.ReferenceQueue;
 import java.util.concurrent.ThreadLocalRandom;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
 import java.util.function.Consumer;
 
 
@@ -1036,6 +1038,48 @@ public class WeakHashMap<K,V>
         }
     }
 
+    @Override
+    public void forEach(BiConsumer<? super K, ? super V> action) {
+        Objects.requireNonNull(action);
+        int expectedModCount = modCount;
+
+        Entry<K, V>[] tab = getTable();
+        for (Entry<K, V> entry : tab) {
+            while (entry != null) {
+                Object key = entry.get();
+                if (key != null) {
+                    action.accept((K)WeakHashMap.unmaskNull(key), entry.value);
+                }
+                entry = entry.next;
+
+                if (expectedModCount != modCount) {
+                    throw new ConcurrentModificationException();
+                }
+            }
+        }
+    }
+
+    @Override
+    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);
+        int expectedModCount = modCount;
+
+        Entry<K, V>[] tab = getTable();;
+        for (Entry<K, V> entry : tab) {
+            while (entry != null) {
+                Object key = entry.get();
+                if (key != null) {
+                    entry.value = function.apply((K)WeakHashMap.unmaskNull(key), entry.value);
+                }
+                entry = entry.next;
+
+                if (expectedModCount != modCount) {
+                    throw new ConcurrentModificationException();
+                }
+            }
+        }
+    }
+
     /**
      * Similar form as other hash Spliterators, but skips dead
      * elements.

jdk/src/share/classes/java/util/concurrent/ConcurrentMap.java

@@ -35,6 +35,8 @@
 
 package java.util.concurrent;
 import java.util.Map;
+import java.util.Objects;
+import java.util.function.BiFunction;
 
 /**
  * A {@link java.util.Map} providing additional atomic
@@ -183,4 +185,26 @@ public interface ConcurrentMap<K, V> extends Map<K, V> {
      *         or value prevents it from being stored in this map
      */
     V replace(K key, V value);
+
+    /**
+     * {@inheritDoc}
+     *
+     * @implNote This implementation assumes that the ConcurrentMap cannot
+     * contain null values and get() returning null unambiguously means the key
+     * is absent. Implementations which support null values
+     * <strong>must</strong> override this default implementation.
+     */
+    @Override
+    default void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+        Objects.requireNonNull(function);
+        forEach((k,v) -> {
+            while(!replace(k, v, function.apply(k, v))) {
+                // v changed or k is gone
+                if( (v = get(k)) == null) {
+                    // k is no longer in the map.
+                    break;
+                }
+            }
+        });
+    }
 }

jdk/test/java/util/Map/Defaults.java

@@ -36,6 +36,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.EnumMap;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Hashtable;
 import java.util.IdentityHashMap;
 import java.util.Iterator;
@@ -47,6 +48,7 @@ import java.util.WeakHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentSkipListMap;
+import java.util.function.BiFunction;
 import java.util.function.Supplier;
 
 import org.testng.annotations.Test;
@@ -60,14 +62,14 @@ import static org.testng.Assert.assertSame;
 
 public class Defaults {
 
-    @Test(dataProvider = "Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=all keys=withNull values=withNull")
     public void testGetOrDefaultNulls(String description, Map<IntegerEnum, String> map) {
-        assertTrue(map.containsKey(null), "null key absent");
+        assertTrue(map.containsKey(null), description + ": null key absent");
-        assertNull(map.get(null), "value not null");
+        assertNull(map.get(null), description + ": value not null");
-        assertSame(map.get(null), map.getOrDefault(null, EXTRA_VALUE), "values should match");
+        assertSame(map.get(null), map.getOrDefault(null, EXTRA_VALUE), description + ": values should match");
     }
 
-    @Test(dataProvider = "Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=all keys=all values=all")
     public void testGetOrDefault(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]), "expected key missing");
         assertSame(map.get(KEYS[1]), map.getOrDefault(KEYS[1], EXTRA_VALUE), "values should match");
@@ -76,7 +78,7 @@ public class Defaults {
         assertNull(map.getOrDefault(EXTRA_KEY, null), "null not returned as default");
     }
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public void testPutIfAbsentNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null), "null key absent");
         assertNull(map.get(null), "value not null");
@@ -96,7 +98,7 @@ public class Defaults {
         assertSame(map.get(null), EXTRA_VALUE, "value not expected");
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public void testPutIfAbsent(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object expected = map.get(KEYS[1]);
@@ -109,7 +111,7 @@ public class Defaults {
         assertSame(map.get(EXTRA_KEY), EXTRA_VALUE);
     }
 
-    @Test(dataProvider = "Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=all keys=all values=all")
     public void testForEach(String description, Map<IntegerEnum, String> map) {
         IntegerEnum[] EACH_KEY = new IntegerEnum[map.size()];
 
@@ -120,10 +122,43 @@ public class Defaults {
             assertSame(v, map.get(k));
         });
 
-        assertEquals(KEYS, EACH_KEY);
+        assertEquals(KEYS, EACH_KEY, description);
     }
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
+    public static void testReplaceAll(String description, Map<IntegerEnum, String> map) {
+        IntegerEnum[] EACH_KEY = new IntegerEnum[map.size()];
+        Set<String> EACH_REPLACE = new HashSet<>(map.size());
+
+        map.replaceAll((k,v) -> {
+            int idx = (null == k) ? 0 : k.ordinal(); // substitute for index.
+            assertNull(EACH_KEY[idx]);
+            EACH_KEY[idx] = (idx == 0) ? KEYS[0] : k; // substitute for comparison.
+            assertSame(v, map.get(k));
+            String replacement = v + " replaced";
+            EACH_REPLACE.add(replacement);
+            return replacement;
+        });
+
+        assertEquals(KEYS, EACH_KEY, description);
+        assertEquals(map.values().size(), EACH_REPLACE.size(), description + EACH_REPLACE);
+        assertTrue(EACH_REPLACE.containsAll(map.values()), description + " : " + EACH_REPLACE + " != " + map.values());
+        assertTrue(map.values().containsAll(EACH_REPLACE), description + " : " + EACH_REPLACE + " != " + map.values());
+    }
+
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=nonNull values=nonNull")
+    public static void testReplaceAllNoNullReplacement(String description, Map<IntegerEnum, String> map) {
+        assertThrows(
+            () -> { map.replaceAll(null); },
+            NullPointerException.class,
+            description);
+        assertThrows(
+            () -> { map.replaceAll((k,v) -> null); },
+            NullPointerException.class,
+            description);
+    }
+
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public static void testRemoveNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null), "null key absent");
         assertNull(map.get(null), "value not null");
@@ -136,7 +171,7 @@ public class Defaults {
         assertFalse(map.remove(null, null));
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public static void testRemove(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object expected = map.get(KEYS[1]);
@@ -151,7 +186,7 @@ public class Defaults {
         assertFalse(map.remove(EXTRA_KEY, EXTRA_VALUE));
     }
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public void testReplaceKVNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null), "null key absent");
         assertNull(map.get(null), "value not null");
@@ -159,7 +194,7 @@ public class Defaults {
         assertSame(map.get(null), EXTRA_VALUE);
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public void testReplaceKV(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object expected = map.get(KEYS[1]);
@@ -177,7 +212,7 @@ public class Defaults {
         assertSame(map.get(EXTRA_KEY), expected);
     }
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public void testReplaceKVVNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null), "null key absent");
         assertNull(map.get(null), "value not null");
@@ -189,7 +224,7 @@ public class Defaults {
         assertSame(map.get(null), EXTRA_VALUE);
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public void testReplaceKVV(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object expected = map.get(KEYS[1]);
@@ -212,7 +247,7 @@ public class Defaults {
         assertSame(map.get(EXTRA_KEY), EXTRA_VALUE);
     }
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public void testComputeIfAbsentNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null), "null key absent");
         assertNull(map.get(null), "value not null");
@@ -220,7 +255,7 @@ public class Defaults {
         assertSame(map.get(null), EXTRA_VALUE, description);
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public void testComputeIfAbsent(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object expected = map.get(KEYS[1]);
@@ -234,7 +269,7 @@ public class Defaults {
         assertSame(map.get(EXTRA_KEY), EXTRA_VALUE);
     }
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public void testComputeIfPresentNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null));
         assertNull(map.get(null));
@@ -246,7 +281,7 @@ public class Defaults {
         assertSame(map.get(null), null, description);
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public void testComputeIfPresent(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object value = map.get(KEYS[1]);
@@ -267,7 +302,7 @@ public class Defaults {
         assertSame(map.get(EXTRA_KEY), null);
     }
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public void testComputeNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null), "null key absent");
         assertNull(map.get(null), "value not null");
@@ -287,7 +322,7 @@ public class Defaults {
         }), null, description);
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public void testCompute(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object value = map.get(KEYS[1]);
@@ -314,7 +349,7 @@ public class Defaults {
     }
 
 
-    @Test(dataProvider = "R/W Nulls Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull")
     public void testMergeNulls(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(null), "null key absent");
         assertNull(map.get(null), "value not null");
@@ -327,7 +362,7 @@ public class Defaults {
         assertSame(map.get(null), EXTRA_VALUE, description);
     }
 
-    @Test(dataProvider = "R/W Map<IntegerEnum,String>")
+    @Test(dataProvider = "Map<IntegerEnum,String> rw=true keys=all values=all")
     public void testMerge(String description, Map<IntegerEnum, String> map) {
         assertTrue(map.containsKey(KEYS[1]));
         Object value = map.get(KEYS[1]);
@@ -391,52 +426,58 @@ public class Defaults {
     private static final IntegerEnum EXTRA_KEY = IntegerEnum.EXTRA_KEY;
     private static final String EXTRA_VALUE = String.valueOf(TEST_SIZE);
 
-    @DataProvider(name = "Map<IntegerEnum,String>", parallel = true)
+    @DataProvider(name = "Map<IntegerEnum,String> rw=all keys=all values=all", parallel = true)
-    public static Iterator<Object[]> allNullsMapProvider() {
+    public static Iterator<Object[]> allMapProvider() {
         return makeAllMaps().iterator();
     }
 
-    @DataProvider(name = "Nulls Map<IntegerEnum,String>", parallel = true)
+    @DataProvider(name = "Map<IntegerEnum,String> rw=all keys=withNull values=withNull", parallel = true)
-    public static Iterator<Object[]> allMapProvider() {
+    public static Iterator<Object[]> allMapWithNullsProvider() {
-        return makeRWMaps(true).iterator();
+        return makeAllMapsWithNulls().iterator();
     }
 
-    @DataProvider(name = "R/W Map<IntegerEnum,String>", parallel = true)
+    @DataProvider(name = "Map<IntegerEnum,String> rw=true keys=nonNull values=nonNull", parallel = true)
-    public static Iterator<Object[]> rwMapProvider() {
+    public static Iterator<Object[]> rwNonNullMapProvider() {
+        return makeRWNoNullsMaps().iterator();
+    }
+
+    @DataProvider(name = "Map<IntegerEnum,String> rw=true keys=nonNull values=all", parallel = true)
+    public static Iterator<Object[]> rwNonNullKeysMapProvider() {
         return makeRWMapsNoNulls().iterator();
     }
 
-    @DataProvider(name = "R/W Nulls Map<IntegerEnum,String>", parallel = true)
+    @DataProvider(name = "Map<IntegerEnum,String> rw=true keys=all values=all", parallel = true)
-    public static Iterator<Object[]> rwNullsMapProvider() {
+    public static Iterator<Object[]> rwMapProvider() {
-        return makeRWMaps(true).iterator();
+        return makeAllRWMaps().iterator();
     }
 
-    private static Collection<Object[]> makeAllMapsNoNulls() {
+    @DataProvider(name = "Map<IntegerEnum,String> rw=true keys=withNull values=withNull", parallel = true)
+    public static Iterator<Object[]> rwNullsMapProvider() {
+        return makeAllRWMapsWithNulls().iterator();
+    }
+
+    private static Collection<Object[]> makeAllRWMapsWithNulls() {
         Collection<Object[]> all = new ArrayList<>();
 
-        all.addAll(makeRWMaps(false));
+        all.addAll(makeRWMaps(true, true));
-        all.addAll(makeRWNoNullsMaps());
-        all.addAll(makeROMaps(false));
 
         return all;
     }
 
+
     private static Collection<Object[]> makeRWMapsNoNulls() {
         Collection<Object[]> all = new ArrayList<>();
 
-        all.addAll(makeRWMaps(false));
+        all.addAll(makeRWNoNullKeysMaps(false));
         all.addAll(makeRWNoNullsMaps());
 
         return all;
     }
 
-    private static Collection<Object[]> makeAllMaps() {
+    private static Collection<Object[]> makeAllROMaps() {
         Collection<Object[]> all = new ArrayList<>();
 
         all.addAll(makeROMaps(false));
-        all.addAll(makeRWMaps(false));
-        all.addAll(makeRWNoNullsMaps());
-        all.addAll(makeRWMaps(true));
         all.addAll(makeROMaps(true));
 
         return all;
@@ -445,52 +486,99 @@ public class Defaults {
     private static Collection<Object[]> makeAllRWMaps() {
         Collection<Object[]> all = new ArrayList<>();
 
-        all.addAll(makeRWMaps(false));
         all.addAll(makeRWNoNullsMaps());
-        all.addAll(makeRWMaps(true));
+        all.addAll(makeRWMaps(false,true));
+        all.addAll(makeRWMaps(true,true));
+        all.addAll(makeRWNoNullKeysMaps(true));
+        return all;
+    }
+
+    private static Collection<Object[]> makeAllMaps() {
+        Collection<Object[]> all = new ArrayList<>();
+
+        all.addAll(makeAllROMaps());
+        all.addAll(makeAllRWMaps());
 
         return all;
     }
 
-    private static Collection<Object[]> makeRWMaps(boolean nulls) {
+    private static Collection<Object[]> makeAllMapsWithNulls() {
+        Collection<Object[]> all = new ArrayList<>();
+
+        all.addAll(makeROMaps(true));
+        all.addAll(makeRWMaps(true,true));
+
+        return all;
+    }
+    /**
+     *
+     * @param nullKeys include null keys
+     * @param nullValues include null values
+     * @return
+     */
+    private static Collection<Object[]> makeRWMaps(boolean nullKeys, boolean nullValues) {
         return Arrays.asList(
-            new Object[]{"HashMap", makeMap(HashMap::new, nulls)},
+            new Object[]{"HashMap", makeMap(HashMap::new, nullKeys, nullValues)},
-            new Object[]{"IdentityHashMap", makeMap(IdentityHashMap::new, nulls)},
+            new Object[]{"IdentityHashMap", makeMap(IdentityHashMap::new, nullKeys, nullValues)},
-            new Object[]{"LinkedHashMap", makeMap(LinkedHashMap::new, nulls)},
+            new Object[]{"LinkedHashMap", makeMap(LinkedHashMap::new, nullKeys, nullValues)},
-            new Object[]{"WeakHashMap", makeMap(WeakHashMap::new, nulls)},
+            new Object[]{"WeakHashMap", makeMap(WeakHashMap::new, nullKeys, nullValues)},
-            new Object[]{"Collections.checkedMap(HashMap)", Collections.checkedMap(makeMap(HashMap::new, nulls), IntegerEnum.class, String.class)},
+            new Object[]{"Collections.checkedMap(HashMap)", Collections.checkedMap(makeMap(HashMap::new, nullKeys, nullValues), IntegerEnum.class, String.class)},
-            new Object[]{"Collections.synchronizedMap(HashMap)", Collections.synchronizedMap(makeMap(HashMap::new, nulls))},
+            new Object[]{"Collections.synchronizedMap(HashMap)", Collections.synchronizedMap(makeMap(HashMap::new, nullKeys, nullValues))},
-            new Object[]{"ExtendsAbstractMap", makeMap(ExtendsAbstractMap::new, nulls)});
+            new Object[]{"ExtendsAbstractMap", makeMap(ExtendsAbstractMap::new, nullKeys, nullValues)});
+    }
+
+    /**
+     *
+     * @param nulls include null values
+     * @return
+     */
+    private static Collection<Object[]> makeRWNoNullKeysMaps(boolean nulls) {
+        return Arrays.asList(
+                // null key hostile
+                new Object[]{"EnumMap", makeMap(() -> new EnumMap(IntegerEnum.class), false, nulls)},
+                new Object[]{"Collections.synchronizedMap(EnumMap)", Collections.synchronizedMap(makeMap(() -> new EnumMap(IntegerEnum.class), false, nulls))}
+                );
     }
 
     private static Collection<Object[]> makeRWNoNullsMaps() {
         return Arrays.asList(
-            // null hostile
+            // null key and value hostile
-            new Object[]{"EnumMap", makeMap(() -> new EnumMap(IntegerEnum.class), false)},
+            new Object[]{"Hashtable", makeMap(Hashtable::new, false, false)},
-            new Object[]{"Hashtable", makeMap(Hashtable::new, false)},
+            new Object[]{"TreeMap", makeMap(TreeMap::new, false, false)},
-            new Object[]{"TreeMap", makeMap(TreeMap::new, false)},
+            new Object[]{"ConcurrentHashMap", makeMap(ConcurrentHashMap::new, false, false)},
-            new Object[]{"ConcurrentHashMap", makeMap(ConcurrentHashMap::new, false)},
+            new Object[]{"ConcurrentSkipListMap", makeMap(ConcurrentSkipListMap::new, false, false)},
-            new Object[]{"ConcurrentSkipListMap", makeMap(ConcurrentSkipListMap::new, false)},
+            new Object[]{"Collections.checkedMap(ConcurrentHashMap)", Collections.checkedMap(makeMap(ConcurrentHashMap::new, false, false), IntegerEnum.class, String.class)},
-            new Object[]{"Collections.checkedMap(ConcurrentHashMap)", Collections.checkedMap(makeMap(ConcurrentHashMap::new, false), IntegerEnum.class, String.class)},
+            new Object[]{"ImplementsConcurrentMap", makeMap(ImplementsConcurrentMap::new, false, false)}
-            new Object[]{"Collections.synchronizedMap(EnumMap)", Collections.synchronizedMap(makeMap(() -> new EnumMap(IntegerEnum.class), false))},
+            );
-            new Object[]{"ImplementsConcurrentMap", makeMap(ImplementsConcurrentMap::new, false)});
     }
 
+    /**
+     *
+     * @param nulls include nulls
+     * @return
+     */
     private static Collection<Object[]> makeROMaps(boolean nulls) {
         return Arrays.asList(new Object[][]{
-            new Object[]{"Collections.unmodifiableMap(HashMap)", Collections.unmodifiableMap(makeMap(HashMap::new, nulls))}
+            new Object[]{"Collections.unmodifiableMap(HashMap)", Collections.unmodifiableMap(makeMap(HashMap::new, nulls, nulls))}
         });
     }
 
-    private static Map<IntegerEnum, String> makeMap(Supplier<Map<IntegerEnum, String>> supplier, boolean nulls) {
+     /**
+     *
+     * @param supplier a supplier of mutable map instances.
+     *
+     * @param nullKeys   include null keys
+     * @param nullValues include null values
+     * @return
+     */
+    private static Map<IntegerEnum, String> makeMap(Supplier<Map<IntegerEnum, String>> supplier, boolean nullKeys, boolean nullValues) {
         Map<IntegerEnum, String> result = supplier.get();
 
         for (int each = 0; each < TEST_SIZE; each++) {
-            if (nulls) {
+            IntegerEnum key = nullKeys ? (each == 0) ? null : KEYS[each] : KEYS[each];
-                result.put((each == 0) ? null : KEYS[each], null);
+            String value = nullValues ? (each == 0) ? null : VALUES[each] : VALUES[each];
-            } else {
+
-                result.put(KEYS[each], VALUES[each]);
+            result.put(key, value);
-            }
         }
 
         return result;
@@ -520,6 +608,12 @@ public class Defaults {
             : "Failed to throw " + throwable.getCanonicalName());
     }
 
+    public static <T extends Throwable> void assertThrows(Class<T> throwable, String message, Thrower<T>... throwers) {
+        for(Thrower<T> thrower : throwers) {
+            assertThrows(thrower, throwable, message);
+        }
+    }
+
     public static <T> void assertInstance(T actual, Class<? extends T> expected) {
         assertInstance(expected.isInstance(actual), null);
     }