--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/java/util/WeakHashMap.java Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,1340 @@
+/*
+ * Copyright (c) 1998, 2013, 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. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+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;
+
+
+/**
+ * Hash table based implementation of the {@code Map} interface, with
+ * <em>weak keys</em>.
+ * An entry in a {@code WeakHashMap} will automatically be removed when
+ * its key is no longer in ordinary use. More precisely, the presence of a
+ * mapping for a given key will not prevent the key from being discarded by the
+ * garbage collector, that is, made finalizable, finalized, and then reclaimed.
+ * When a key has been discarded its entry is effectively removed from the map,
+ * so this class behaves somewhat differently from other {@code Map}
+ * implementations.
+ *
+ * <p> Both null values and the null key are supported. This class has
+ * performance characteristics similar to those of the {@code HashMap}
+ * class, and has the same efficiency parameters of <em>initial capacity</em>
+ * and <em>load factor</em>.
+ *
+ * <p> Like most collection classes, this class is not synchronized.
+ * A synchronized {@code WeakHashMap} may be constructed using the
+ * {@link Collections#synchronizedMap Collections.synchronizedMap}
+ * method.
+ *
+ * <p> This class is intended primarily for use with key objects whose
+ * {@code equals} methods test for object identity using the
+ * {@code ==} operator. Once such a key is discarded it can never be
+ * recreated, so it is impossible to do a lookup of that key in a
+ * {@code WeakHashMap} at some later time and be surprised that its entry
+ * has been removed. This class will work perfectly well with key objects
+ * whose {@code equals} methods are not based upon object identity, such
+ * as {@code String} instances. With such recreatable key objects,
+ * however, the automatic removal of {@code WeakHashMap} entries whose
+ * keys have been discarded may prove to be confusing.
+ *
+ * <p> The behavior of the {@code WeakHashMap} class depends in part upon
+ * the actions of the garbage collector, so several familiar (though not
+ * required) {@code Map} invariants do not hold for this class. Because
+ * the garbage collector may discard keys at any time, a
+ * {@code WeakHashMap} may behave as though an unknown thread is silently
+ * removing entries. In particular, even if you synchronize on a
+ * {@code WeakHashMap} instance and invoke none of its mutator methods, it
+ * is possible for the {@code size} method to return smaller values over
+ * time, for the {@code isEmpty} method to return {@code false} and
+ * then {@code true}, for the {@code containsKey} method to return
+ * {@code true} and later {@code false} for a given key, for the
+ * {@code get} method to return a value for a given key but later return
+ * {@code null}, for the {@code put} method to return
+ * {@code null} and the {@code remove} method to return
+ * {@code false} for a key that previously appeared to be in the map, and
+ * for successive examinations of the key set, the value collection, and
+ * the entry set to yield successively smaller numbers of elements.
+ *
+ * <p> Each key object in a {@code WeakHashMap} is stored indirectly as
+ * the referent of a weak reference. Therefore a key will automatically be
+ * removed only after the weak references to it, both inside and outside of the
+ * map, have been cleared by the garbage collector.
+ *
+ * <p> <strong>Implementation note:</strong> The value objects in a
+ * {@code WeakHashMap} are held by ordinary strong references. Thus care
+ * should be taken to ensure that value objects do not strongly refer to their
+ * own keys, either directly or indirectly, since that will prevent the keys
+ * from being discarded. Note that a value object may refer indirectly to its
+ * key via the {@code WeakHashMap} itself; that is, a value object may
+ * strongly refer to some other key object whose associated value object, in
+ * turn, strongly refers to the key of the first value object. If the values
+ * in the map do not rely on the map holding strong references to them, one way
+ * to deal with this is to wrap values themselves within
+ * {@code WeakReferences} before
+ * inserting, as in: {@code m.put(key, new WeakReference(value))},
+ * and then unwrapping upon each {@code get}.
+ *
+ * <p>The iterators returned by the {@code iterator} method of the collections
+ * returned by all of this class's "collection view methods" are
+ * <i>fail-fast</i>: if the map is structurally modified at any time after the
+ * iterator is created, in any way except through the iterator's own
+ * {@code remove} method, the iterator will throw a {@link
+ * ConcurrentModificationException}. Thus, in the face of concurrent
+ * modification, the iterator fails quickly and cleanly, rather than risking
+ * arbitrary, non-deterministic behavior at an undetermined time in the future.
+ *
+ * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
+ * as it is, generally speaking, impossible to make any hard guarantees in the
+ * presence of unsynchronized concurrent modification. Fail-fast iterators
+ * throw {@code ConcurrentModificationException} on a best-effort basis.
+ * Therefore, it would be wrong to write a program that depended on this
+ * exception for its correctness: <i>the fail-fast behavior of iterators
+ * should be used only to detect bugs.</i>
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @param <K> the type of keys maintained by this map
+ * @param <V> the type of mapped values
+ *
+ * @author Doug Lea
+ * @author Josh Bloch
+ * @author Mark Reinhold
+ * @since 1.2
+ * @see java.util.HashMap
+ * @see java.lang.ref.WeakReference
+ */
+public class WeakHashMap<K,V>
+ extends AbstractMap<K,V>
+ implements Map<K,V> {
+
+ /**
+ * The default initial capacity -- MUST be a power of two.
+ */
+ private static final int DEFAULT_INITIAL_CAPACITY = 16;
+
+ /**
+ * The maximum capacity, used if a higher value is implicitly specified
+ * by either of the constructors with arguments.
+ * MUST be a power of two <= 1<<30.
+ */
+ private static final int MAXIMUM_CAPACITY = 1 << 30;
+
+ /**
+ * The load factor used when none specified in constructor.
+ */
+ private static final float DEFAULT_LOAD_FACTOR = 0.75f;
+
+ /**
+ * The table, resized as necessary. Length MUST Always be a power of two.
+ */
+ Entry<K,V>[] table;
+
+ /**
+ * The number of key-value mappings contained in this weak hash map.
+ */
+ private int size;
+
+ /**
+ * The next size value at which to resize (capacity * load factor).
+ */
+ private int threshold;
+
+ /**
+ * The load factor for the hash table.
+ */
+ private final float loadFactor;
+
+ /**
+ * Reference queue for cleared WeakEntries
+ */
+ private final ReferenceQueue<Object> queue = new ReferenceQueue<>();
+
+ /**
+ * The number of times this WeakHashMap has been structurally modified.
+ * Structural modifications are those that change the number of
+ * mappings in the map or otherwise modify its internal structure
+ * (e.g., rehash). This field is used to make iterators on
+ * Collection-views of the map fail-fast.
+ *
+ * @see ConcurrentModificationException
+ */
+ int modCount;
+
+ @SuppressWarnings("unchecked")
+ private Entry<K,V>[] newTable(int n) {
+ return (Entry<K,V>[]) new Entry<?,?>[n];
+ }
+
+ /**
+ * Constructs a new, empty {@code WeakHashMap} with the given initial
+ * capacity and the given load factor.
+ *
+ * @param initialCapacity The initial capacity of the {@code WeakHashMap}
+ * @param loadFactor The load factor of the {@code WeakHashMap}
+ * @throws IllegalArgumentException if the initial capacity is negative,
+ * or if the load factor is nonpositive.
+ */
+ public WeakHashMap(int initialCapacity, float loadFactor) {
+ if (initialCapacity < 0)
+ throw new IllegalArgumentException("Illegal Initial Capacity: "+
+ initialCapacity);
+ if (initialCapacity > MAXIMUM_CAPACITY)
+ initialCapacity = MAXIMUM_CAPACITY;
+
+ if (loadFactor <= 0 || Float.isNaN(loadFactor))
+ throw new IllegalArgumentException("Illegal Load factor: "+
+ loadFactor);
+ int capacity = 1;
+ while (capacity < initialCapacity)
+ capacity <<= 1;
+ table = newTable(capacity);
+ this.loadFactor = loadFactor;
+ threshold = (int)(capacity * loadFactor);
+ }
+
+ /**
+ * Constructs a new, empty {@code WeakHashMap} with the given initial
+ * capacity and the default load factor (0.75).
+ *
+ * @param initialCapacity The initial capacity of the {@code WeakHashMap}
+ * @throws IllegalArgumentException if the initial capacity is negative
+ */
+ public WeakHashMap(int initialCapacity) {
+ this(initialCapacity, DEFAULT_LOAD_FACTOR);
+ }
+
+ /**
+ * Constructs a new, empty {@code WeakHashMap} with the default initial
+ * capacity (16) and load factor (0.75).
+ */
+ public WeakHashMap() {
+ this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
+ }
+
+ /**
+ * Constructs a new {@code WeakHashMap} with the same mappings as the
+ * specified map. The {@code WeakHashMap} is created with the default
+ * load factor (0.75) and an initial capacity sufficient to hold the
+ * mappings in the specified map.
+ *
+ * @param m the map whose mappings are to be placed in this map
+ * @throws NullPointerException if the specified map is null
+ * @since 1.3
+ */
+ public WeakHashMap(Map<? extends K, ? extends V> m) {
+ this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
+ DEFAULT_INITIAL_CAPACITY),
+ DEFAULT_LOAD_FACTOR);
+ putAll(m);
+ }
+
+ // internal utilities
+
+ /**
+ * Value representing null keys inside tables.
+ */
+ private static final Object NULL_KEY = new Object();
+
+ /**
+ * Use NULL_KEY for key if it is null.
+ */
+ private static Object maskNull(Object key) {
+ return (key == null) ? NULL_KEY : key;
+ }
+
+ /**
+ * Returns internal representation of null key back to caller as null.
+ */
+ static Object unmaskNull(Object key) {
+ return (key == NULL_KEY) ? null : key;
+ }
+
+ /**
+ * Checks for equality of non-null reference x and possibly-null y. By
+ * default uses Object.equals.
+ */
+ private static boolean eq(Object x, Object y) {
+ return x == y || x.equals(y);
+ }
+
+ /**
+ * Retrieve object hash code and applies a supplemental hash function to the
+ * result hash, which defends against poor quality hash functions. This is
+ * critical because HashMap uses power-of-two length hash tables, that
+ * otherwise encounter collisions for hashCodes that do not differ
+ * in lower bits.
+ */
+ final int hash(Object k) {
+ int h = k.hashCode();
+
+ // This function ensures that hashCodes that differ only by
+ // constant multiples at each bit position have a bounded
+ // number of collisions (approximately 8 at default load factor).
+ h ^= (h >>> 20) ^ (h >>> 12);
+ return h ^ (h >>> 7) ^ (h >>> 4);
+ }
+
+ /**
+ * Returns index for hash code h.
+ */
+ private static int indexFor(int h, int length) {
+ return h & (length-1);
+ }
+
+ /**
+ * Expunges stale entries from the table.
+ */
+ private void expungeStaleEntries() {
+ for (Object x; (x = queue.poll()) != null; ) {
+ synchronized (queue) {
+ @SuppressWarnings("unchecked")
+ Entry<K,V> e = (Entry<K,V>) x;
+ int i = indexFor(e.hash, table.length);
+
+ Entry<K,V> prev = table[i];
+ Entry<K,V> p = prev;
+ while (p != null) {
+ Entry<K,V> next = p.next;
+ if (p == e) {
+ if (prev == e)
+ table[i] = next;
+ else
+ prev.next = next;
+ // Must not null out e.next;
+ // stale entries may be in use by a HashIterator
+ e.value = null; // Help GC
+ size--;
+ break;
+ }
+ prev = p;
+ p = next;
+ }
+ }
+ }
+ }
+
+ /**
+ * Returns the table after first expunging stale entries.
+ */
+ private Entry<K,V>[] getTable() {
+ expungeStaleEntries();
+ return table;
+ }
+
+ /**
+ * Returns the number of key-value mappings in this map.
+ * This result is a snapshot, and may not reflect unprocessed
+ * entries that will be removed before next attempted access
+ * because they are no longer referenced.
+ */
+ public int size() {
+ if (size == 0)
+ return 0;
+ expungeStaleEntries();
+ return size;
+ }
+
+ /**
+ * Returns {@code true} if this map contains no key-value mappings.
+ * This result is a snapshot, and may not reflect unprocessed
+ * entries that will be removed before next attempted access
+ * because they are no longer referenced.
+ */
+ public boolean isEmpty() {
+ return size() == 0;
+ }
+
+ /**
+ * Returns the value to which the specified key is mapped,
+ * or {@code null} if this map contains no mapping for the key.
+ *
+ * <p>More formally, if this map contains a mapping from a key
+ * {@code k} to a value {@code v} such that
+ * {@code Objects.equals(key, k)},
+ * then this method returns {@code v}; otherwise
+ * it returns {@code null}. (There can be at most one such mapping.)
+ *
+ * <p>A return value of {@code null} does not <i>necessarily</i>
+ * indicate that the map contains no mapping for the key; it's also
+ * possible that the map explicitly maps the key to {@code null}.
+ * The {@link #containsKey containsKey} operation may be used to
+ * distinguish these two cases.
+ *
+ * @see #put(Object, Object)
+ */
+ public V get(Object key) {
+ Object k = maskNull(key);
+ int h = hash(k);
+ Entry<K,V>[] tab = getTable();
+ int index = indexFor(h, tab.length);
+ Entry<K,V> e = tab[index];
+ while (e != null) {
+ if (e.hash == h && eq(k, e.get()))
+ return e.value;
+ e = e.next;
+ }
+ return null;
+ }
+
+ /**
+ * Returns {@code true} if this map contains a mapping for the
+ * specified key.
+ *
+ * @param key The key whose presence in this map is to be tested
+ * @return {@code true} if there is a mapping for {@code key};
+ * {@code false} otherwise
+ */
+ public boolean containsKey(Object key) {
+ return getEntry(key) != null;
+ }
+
+ /**
+ * Returns the entry associated with the specified key in this map.
+ * Returns null if the map contains no mapping for this key.
+ */
+ Entry<K,V> getEntry(Object key) {
+ Object k = maskNull(key);
+ int h = hash(k);
+ Entry<K,V>[] tab = getTable();
+ int index = indexFor(h, tab.length);
+ Entry<K,V> e = tab[index];
+ while (e != null && !(e.hash == h && eq(k, e.get())))
+ e = e.next;
+ return e;
+ }
+
+ /**
+ * Associates the specified value with the specified key in this map.
+ * If the map previously contained a mapping for this key, the old
+ * value is replaced.
+ *
+ * @param key key with which the specified value is to be associated.
+ * @param value value to be associated with the specified key.
+ * @return the previous value associated with {@code key}, or
+ * {@code null} if there was no mapping for {@code key}.
+ * (A {@code null} return can also indicate that the map
+ * previously associated {@code null} with {@code key}.)
+ */
+ public V put(K key, V value) {
+ Object k = maskNull(key);
+ int h = hash(k);
+ Entry<K,V>[] tab = getTable();
+ int i = indexFor(h, tab.length);
+
+ for (Entry<K,V> e = tab[i]; e != null; e = e.next) {
+ if (h == e.hash && eq(k, e.get())) {
+ V oldValue = e.value;
+ if (value != oldValue)
+ e.value = value;
+ return oldValue;
+ }
+ }
+
+ modCount++;
+ Entry<K,V> e = tab[i];
+ tab[i] = new Entry<>(k, value, queue, h, e);
+ if (++size >= threshold)
+ resize(tab.length * 2);
+ return null;
+ }
+
+ /**
+ * Rehashes the contents of this map into a new array with a
+ * larger capacity. This method is called automatically when the
+ * number of keys in this map reaches its threshold.
+ *
+ * If current capacity is MAXIMUM_CAPACITY, this method does not
+ * resize the map, but sets threshold to Integer.MAX_VALUE.
+ * This has the effect of preventing future calls.
+ *
+ * @param newCapacity the new capacity, MUST be a power of two;
+ * must be greater than current capacity unless current
+ * capacity is MAXIMUM_CAPACITY (in which case value
+ * is irrelevant).
+ */
+ void resize(int newCapacity) {
+ Entry<K,V>[] oldTable = getTable();
+ int oldCapacity = oldTable.length;
+ if (oldCapacity == MAXIMUM_CAPACITY) {
+ threshold = Integer.MAX_VALUE;
+ return;
+ }
+
+ Entry<K,V>[] newTable = newTable(newCapacity);
+ transfer(oldTable, newTable);
+ table = newTable;
+
+ /*
+ * If ignoring null elements and processing ref queue caused massive
+ * shrinkage, then restore old table. This should be rare, but avoids
+ * unbounded expansion of garbage-filled tables.
+ */
+ if (size >= threshold / 2) {
+ threshold = (int)(newCapacity * loadFactor);
+ } else {
+ expungeStaleEntries();
+ transfer(newTable, oldTable);
+ table = oldTable;
+ }
+ }
+
+ /** Transfers all entries from src to dest tables */
+ private void transfer(Entry<K,V>[] src, Entry<K,V>[] dest) {
+ for (int j = 0; j < src.length; ++j) {
+ Entry<K,V> e = src[j];
+ src[j] = null;
+ while (e != null) {
+ Entry<K,V> next = e.next;
+ Object key = e.get();
+ if (key == null) {
+ e.next = null; // Help GC
+ e.value = null; // " "
+ size--;
+ } else {
+ int i = indexFor(e.hash, dest.length);
+ e.next = dest[i];
+ dest[i] = e;
+ }
+ e = next;
+ }
+ }
+ }
+
+ /**
+ * Copies all of the mappings from the specified map to this map.
+ * These mappings will replace any mappings that this map had for any
+ * of the keys currently in the specified map.
+ *
+ * @param m mappings to be stored in this map.
+ * @throws NullPointerException if the specified map is null.
+ */
+ public void putAll(Map<? extends K, ? extends V> m) {
+ int numKeysToBeAdded = m.size();
+ if (numKeysToBeAdded == 0)
+ return;
+
+ /*
+ * Expand the map if the map if the number of mappings to be added
+ * is greater than or equal to threshold. This is conservative; the
+ * obvious condition is (m.size() + size) >= threshold, but this
+ * condition could result in a map with twice the appropriate capacity,
+ * if the keys to be added overlap with the keys already in this map.
+ * By using the conservative calculation, we subject ourself
+ * to at most one extra resize.
+ */
+ if (numKeysToBeAdded > threshold) {
+ int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
+ if (targetCapacity > MAXIMUM_CAPACITY)
+ targetCapacity = MAXIMUM_CAPACITY;
+ int newCapacity = table.length;
+ while (newCapacity < targetCapacity)
+ newCapacity <<= 1;
+ if (newCapacity > table.length)
+ resize(newCapacity);
+ }
+
+ for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
+ put(e.getKey(), e.getValue());
+ }
+
+ /**
+ * Removes the mapping for a key from this weak hash map if it is present.
+ * More formally, if this map contains a mapping from key {@code k} to
+ * value {@code v} such that <code>(key==null ? k==null :
+ * key.equals(k))</code>, that mapping is removed. (The map can contain
+ * at most one such mapping.)
+ *
+ * <p>Returns the value to which this map previously associated the key,
+ * or {@code null} if the map contained no mapping for the key. A
+ * return value of {@code null} does not <i>necessarily</i> indicate
+ * that the map contained no mapping for the key; it's also possible
+ * that the map explicitly mapped the key to {@code null}.
+ *
+ * <p>The map will not contain a mapping for the specified key once the
+ * call returns.
+ *
+ * @param key key whose mapping is to be removed from the map
+ * @return the previous value associated with {@code key}, or
+ * {@code null} if there was no mapping for {@code key}
+ */
+ public V remove(Object key) {
+ Object k = maskNull(key);
+ int h = hash(k);
+ Entry<K,V>[] tab = getTable();
+ int i = indexFor(h, tab.length);
+ Entry<K,V> prev = tab[i];
+ Entry<K,V> e = prev;
+
+ while (e != null) {
+ Entry<K,V> next = e.next;
+ if (h == e.hash && eq(k, e.get())) {
+ modCount++;
+ size--;
+ if (prev == e)
+ tab[i] = next;
+ else
+ prev.next = next;
+ return e.value;
+ }
+ prev = e;
+ e = next;
+ }
+
+ return null;
+ }
+
+ /** Special version of remove needed by Entry set */
+ boolean removeMapping(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Entry<K,V>[] tab = getTable();
+ Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
+ Object k = maskNull(entry.getKey());
+ int h = hash(k);
+ int i = indexFor(h, tab.length);
+ Entry<K,V> prev = tab[i];
+ Entry<K,V> e = prev;
+
+ while (e != null) {
+ Entry<K,V> next = e.next;
+ if (h == e.hash && e.equals(entry)) {
+ modCount++;
+ size--;
+ if (prev == e)
+ tab[i] = next;
+ else
+ prev.next = next;
+ return true;
+ }
+ prev = e;
+ e = next;
+ }
+
+ return false;
+ }
+
+ /**
+ * Removes all of the mappings from this map.
+ * The map will be empty after this call returns.
+ */
+ public void clear() {
+ // clear out ref queue. We don't need to expunge entries
+ // since table is getting cleared.
+ while (queue.poll() != null)
+ ;
+
+ modCount++;
+ Arrays.fill(table, null);
+ size = 0;
+
+ // Allocation of array may have caused GC, which may have caused
+ // additional entries to go stale. Removing these entries from the
+ // reference queue will make them eligible for reclamation.
+ while (queue.poll() != null)
+ ;
+ }
+
+ /**
+ * Returns {@code true} if this map maps one or more keys to the
+ * specified value.
+ *
+ * @param value value whose presence in this map is to be tested
+ * @return {@code true} if this map maps one or more keys to the
+ * specified value
+ */
+ public boolean containsValue(Object value) {
+ if (value==null)
+ return containsNullValue();
+
+ Entry<K,V>[] tab = getTable();
+ for (int i = tab.length; i-- > 0;)
+ for (Entry<K,V> e = tab[i]; e != null; e = e.next)
+ if (value.equals(e.value))
+ return true;
+ return false;
+ }
+
+ /**
+ * Special-case code for containsValue with null argument
+ */
+ private boolean containsNullValue() {
+ Entry<K,V>[] tab = getTable();
+ for (int i = tab.length; i-- > 0;)
+ for (Entry<K,V> e = tab[i]; e != null; e = e.next)
+ if (e.value==null)
+ return true;
+ return false;
+ }
+
+ /**
+ * The entries in this hash table extend WeakReference, using its main ref
+ * field as the key.
+ */
+ private static class Entry<K,V> extends WeakReference<Object> implements Map.Entry<K,V> {
+ V value;
+ final int hash;
+ Entry<K,V> next;
+
+ /**
+ * Creates new entry.
+ */
+ Entry(Object key, V value,
+ ReferenceQueue<Object> queue,
+ int hash, Entry<K,V> next) {
+ super(key, queue);
+ this.value = value;
+ this.hash = hash;
+ this.next = next;
+ }
+
+ @SuppressWarnings("unchecked")
+ public K getKey() {
+ return (K) WeakHashMap.unmaskNull(get());
+ }
+
+ public V getValue() {
+ return value;
+ }
+
+ public V setValue(V newValue) {
+ V oldValue = value;
+ value = newValue;
+ return oldValue;
+ }
+
+ public boolean equals(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry<?,?> e = (Map.Entry<?,?>)o;
+ K k1 = getKey();
+ Object k2 = e.getKey();
+ if (k1 == k2 || (k1 != null && k1.equals(k2))) {
+ V v1 = getValue();
+ Object v2 = e.getValue();
+ if (v1 == v2 || (v1 != null && v1.equals(v2)))
+ return true;
+ }
+ return false;
+ }
+
+ public int hashCode() {
+ K k = getKey();
+ V v = getValue();
+ return Objects.hashCode(k) ^ Objects.hashCode(v);
+ }
+
+ public String toString() {
+ return getKey() + "=" + getValue();
+ }
+ }
+
+ private abstract class HashIterator<T> implements Iterator<T> {
+ private int index;
+ private Entry<K,V> entry;
+ private Entry<K,V> lastReturned;
+ private int expectedModCount = modCount;
+
+ /**
+ * Strong reference needed to avoid disappearance of key
+ * between hasNext and next
+ */
+ private Object nextKey;
+
+ /**
+ * Strong reference needed to avoid disappearance of key
+ * between nextEntry() and any use of the entry
+ */
+ private Object currentKey;
+
+ HashIterator() {
+ index = isEmpty() ? 0 : table.length;
+ }
+
+ public boolean hasNext() {
+ Entry<K,V>[] t = table;
+
+ while (nextKey == null) {
+ Entry<K,V> e = entry;
+ int i = index;
+ while (e == null && i > 0)
+ e = t[--i];
+ entry = e;
+ index = i;
+ if (e == null) {
+ currentKey = null;
+ return false;
+ }
+ nextKey = e.get(); // hold on to key in strong ref
+ if (nextKey == null)
+ entry = entry.next;
+ }
+ return true;
+ }
+
+ /** The common parts of next() across different types of iterators */
+ protected Entry<K,V> nextEntry() {
+ if (modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+ if (nextKey == null && !hasNext())
+ throw new NoSuchElementException();
+
+ lastReturned = entry;
+ entry = entry.next;
+ currentKey = nextKey;
+ nextKey = null;
+ return lastReturned;
+ }
+
+ public void remove() {
+ if (lastReturned == null)
+ throw new IllegalStateException();
+ if (modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+
+ WeakHashMap.this.remove(currentKey);
+ expectedModCount = modCount;
+ lastReturned = null;
+ currentKey = null;
+ }
+
+ }
+
+ private class ValueIterator extends HashIterator<V> {
+ public V next() {
+ return nextEntry().value;
+ }
+ }
+
+ private class KeyIterator extends HashIterator<K> {
+ public K next() {
+ return nextEntry().getKey();
+ }
+ }
+
+ private class EntryIterator extends HashIterator<Map.Entry<K,V>> {
+ public Map.Entry<K,V> next() {
+ return nextEntry();
+ }
+ }
+
+ // Views
+
+ private transient Set<Map.Entry<K,V>> entrySet;
+
+ /**
+ * Returns a {@link Set} view of the keys contained in this map.
+ * The set is backed by the map, so changes to the map are
+ * reflected in the set, and vice-versa. If the map is modified
+ * while an iteration over the set is in progress (except through
+ * the iterator's own {@code remove} operation), the results of
+ * the iteration are undefined. The set supports element removal,
+ * which removes the corresponding mapping from the map, via the
+ * {@code Iterator.remove}, {@code Set.remove},
+ * {@code removeAll}, {@code retainAll}, and {@code clear}
+ * operations. It does not support the {@code add} or {@code addAll}
+ * operations.
+ */
+ public Set<K> keySet() {
+ Set<K> ks = keySet;
+ if (ks == null) {
+ ks = new KeySet();
+ keySet = ks;
+ }
+ return ks;
+ }
+
+ private class KeySet extends AbstractSet<K> {
+ public Iterator<K> iterator() {
+ return new KeyIterator();
+ }
+
+ public int size() {
+ return WeakHashMap.this.size();
+ }
+
+ public boolean contains(Object o) {
+ return containsKey(o);
+ }
+
+ public boolean remove(Object o) {
+ if (containsKey(o)) {
+ WeakHashMap.this.remove(o);
+ return true;
+ }
+ else
+ return false;
+ }
+
+ public void clear() {
+ WeakHashMap.this.clear();
+ }
+
+ public Spliterator<K> spliterator() {
+ return new KeySpliterator<>(WeakHashMap.this, 0, -1, 0, 0);
+ }
+ }
+
+ /**
+ * Returns a {@link Collection} view of the values contained in this map.
+ * The collection is backed by the map, so changes to the map are
+ * reflected in the collection, and vice-versa. If the map is
+ * modified while an iteration over the collection is in progress
+ * (except through the iterator's own {@code remove} operation),
+ * the results of the iteration are undefined. The collection
+ * supports element removal, which removes the corresponding
+ * mapping from the map, via the {@code Iterator.remove},
+ * {@code Collection.remove}, {@code removeAll},
+ * {@code retainAll} and {@code clear} operations. It does not
+ * support the {@code add} or {@code addAll} operations.
+ */
+ public Collection<V> values() {
+ Collection<V> vs = values;
+ if (vs == null) {
+ vs = new Values();
+ values = vs;
+ }
+ return vs;
+ }
+
+ private class Values extends AbstractCollection<V> {
+ public Iterator<V> iterator() {
+ return new ValueIterator();
+ }
+
+ public int size() {
+ return WeakHashMap.this.size();
+ }
+
+ public boolean contains(Object o) {
+ return containsValue(o);
+ }
+
+ public void clear() {
+ WeakHashMap.this.clear();
+ }
+
+ public Spliterator<V> spliterator() {
+ return new ValueSpliterator<>(WeakHashMap.this, 0, -1, 0, 0);
+ }
+ }
+
+ /**
+ * Returns a {@link Set} view of the mappings contained in this map.
+ * The set is backed by the map, so changes to the map are
+ * reflected in the set, and vice-versa. If the map is modified
+ * while an iteration over the set is in progress (except through
+ * the iterator's own {@code remove} operation, or through the
+ * {@code setValue} operation on a map entry returned by the
+ * iterator) the results of the iteration are undefined. The set
+ * supports element removal, which removes the corresponding
+ * mapping from the map, via the {@code Iterator.remove},
+ * {@code Set.remove}, {@code removeAll}, {@code retainAll} and
+ * {@code clear} operations. It does not support the
+ * {@code add} or {@code addAll} operations.
+ */
+ public Set<Map.Entry<K,V>> entrySet() {
+ Set<Map.Entry<K,V>> es = entrySet;
+ return es != null ? es : (entrySet = new EntrySet());
+ }
+
+ private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
+ public Iterator<Map.Entry<K,V>> iterator() {
+ return new EntryIterator();
+ }
+
+ public boolean contains(Object o) {
+ if (!(o instanceof Map.Entry))
+ return false;
+ Map.Entry<?,?> e = (Map.Entry<?,?>)o;
+ Entry<K,V> candidate = getEntry(e.getKey());
+ return candidate != null && candidate.equals(e);
+ }
+
+ public boolean remove(Object o) {
+ return removeMapping(o);
+ }
+
+ public int size() {
+ return WeakHashMap.this.size();
+ }
+
+ public void clear() {
+ WeakHashMap.this.clear();
+ }
+
+ private List<Map.Entry<K,V>> deepCopy() {
+ List<Map.Entry<K,V>> list = new ArrayList<>(size());
+ for (Map.Entry<K,V> e : this)
+ list.add(new AbstractMap.SimpleEntry<>(e));
+ return list;
+ }
+
+ public Object[] toArray() {
+ return deepCopy().toArray();
+ }
+
+ public <T> T[] toArray(T[] a) {
+ return deepCopy().toArray(a);
+ }
+
+ public Spliterator<Map.Entry<K,V>> spliterator() {
+ return new EntrySpliterator<>(WeakHashMap.this, 0, -1, 0, 0);
+ }
+ }
+
+ @SuppressWarnings("unchecked")
+ @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();
+ }
+ }
+ }
+ }
+
+ @SuppressWarnings("unchecked")
+ @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.
+ */
+ static class WeakHashMapSpliterator<K,V> {
+ final WeakHashMap<K,V> map;
+ WeakHashMap.Entry<K,V> current; // current node
+ int index; // current index, modified on advance/split
+ int fence; // -1 until first use; then one past last index
+ int est; // size estimate
+ int expectedModCount; // for comodification checks
+
+ WeakHashMapSpliterator(WeakHashMap<K,V> m, int origin,
+ int fence, int est,
+ int expectedModCount) {
+ this.map = m;
+ this.index = origin;
+ this.fence = fence;
+ this.est = est;
+ this.expectedModCount = expectedModCount;
+ }
+
+ final int getFence() { // initialize fence and size on first use
+ int hi;
+ if ((hi = fence) < 0) {
+ WeakHashMap<K,V> m = map;
+ est = m.size();
+ expectedModCount = m.modCount;
+ hi = fence = m.table.length;
+ }
+ return hi;
+ }
+
+ public final long estimateSize() {
+ getFence(); // force init
+ return (long) est;
+ }
+ }
+
+ static final class KeySpliterator<K,V>
+ extends WeakHashMapSpliterator<K,V>
+ implements Spliterator<K> {
+ KeySpliterator(WeakHashMap<K,V> m, int origin, int fence, int est,
+ int expectedModCount) {
+ super(m, origin, fence, est, expectedModCount);
+ }
+
+ public KeySpliterator<K,V> trySplit() {
+ int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
+ return (lo >= mid) ? null :
+ new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
+ expectedModCount);
+ }
+
+ public void forEachRemaining(Consumer<? super K> action) {
+ int i, hi, mc;
+ if (action == null)
+ throw new NullPointerException();
+ WeakHashMap<K,V> m = map;
+ WeakHashMap.Entry<K,V>[] tab = m.table;
+ if ((hi = fence) < 0) {
+ mc = expectedModCount = m.modCount;
+ hi = fence = tab.length;
+ }
+ else
+ mc = expectedModCount;
+ if (tab.length >= hi && (i = index) >= 0 &&
+ (i < (index = hi) || current != null)) {
+ WeakHashMap.Entry<K,V> p = current;
+ current = null; // exhaust
+ do {
+ if (p == null)
+ p = tab[i++];
+ else {
+ Object x = p.get();
+ p = p.next;
+ if (x != null) {
+ @SuppressWarnings("unchecked") K k =
+ (K) WeakHashMap.unmaskNull(x);
+ action.accept(k);
+ }
+ }
+ } while (p != null || i < hi);
+ }
+ if (m.modCount != mc)
+ throw new ConcurrentModificationException();
+ }
+
+ public boolean tryAdvance(Consumer<? super K> action) {
+ int hi;
+ if (action == null)
+ throw new NullPointerException();
+ WeakHashMap.Entry<K,V>[] tab = map.table;
+ if (tab.length >= (hi = getFence()) && index >= 0) {
+ while (current != null || index < hi) {
+ if (current == null)
+ current = tab[index++];
+ else {
+ Object x = current.get();
+ current = current.next;
+ if (x != null) {
+ @SuppressWarnings("unchecked") K k =
+ (K) WeakHashMap.unmaskNull(x);
+ action.accept(k);
+ if (map.modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+ return true;
+ }
+ }
+ }
+ }
+ return false;
+ }
+
+ public int characteristics() {
+ return Spliterator.DISTINCT;
+ }
+ }
+
+ static final class ValueSpliterator<K,V>
+ extends WeakHashMapSpliterator<K,V>
+ implements Spliterator<V> {
+ ValueSpliterator(WeakHashMap<K,V> m, int origin, int fence, int est,
+ int expectedModCount) {
+ super(m, origin, fence, est, expectedModCount);
+ }
+
+ public ValueSpliterator<K,V> trySplit() {
+ int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
+ return (lo >= mid) ? null :
+ new ValueSpliterator<>(map, lo, index = mid, est >>>= 1,
+ expectedModCount);
+ }
+
+ public void forEachRemaining(Consumer<? super V> action) {
+ int i, hi, mc;
+ if (action == null)
+ throw new NullPointerException();
+ WeakHashMap<K,V> m = map;
+ WeakHashMap.Entry<K,V>[] tab = m.table;
+ if ((hi = fence) < 0) {
+ mc = expectedModCount = m.modCount;
+ hi = fence = tab.length;
+ }
+ else
+ mc = expectedModCount;
+ if (tab.length >= hi && (i = index) >= 0 &&
+ (i < (index = hi) || current != null)) {
+ WeakHashMap.Entry<K,V> p = current;
+ current = null; // exhaust
+ do {
+ if (p == null)
+ p = tab[i++];
+ else {
+ Object x = p.get();
+ V v = p.value;
+ p = p.next;
+ if (x != null)
+ action.accept(v);
+ }
+ } while (p != null || i < hi);
+ }
+ if (m.modCount != mc)
+ throw new ConcurrentModificationException();
+ }
+
+ public boolean tryAdvance(Consumer<? super V> action) {
+ int hi;
+ if (action == null)
+ throw new NullPointerException();
+ WeakHashMap.Entry<K,V>[] tab = map.table;
+ if (tab.length >= (hi = getFence()) && index >= 0) {
+ while (current != null || index < hi) {
+ if (current == null)
+ current = tab[index++];
+ else {
+ Object x = current.get();
+ V v = current.value;
+ current = current.next;
+ if (x != null) {
+ action.accept(v);
+ if (map.modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+ return true;
+ }
+ }
+ }
+ }
+ return false;
+ }
+
+ public int characteristics() {
+ return 0;
+ }
+ }
+
+ static final class EntrySpliterator<K,V>
+ extends WeakHashMapSpliterator<K,V>
+ implements Spliterator<Map.Entry<K,V>> {
+ EntrySpliterator(WeakHashMap<K,V> m, int origin, int fence, int est,
+ int expectedModCount) {
+ super(m, origin, fence, est, expectedModCount);
+ }
+
+ public EntrySpliterator<K,V> trySplit() {
+ int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
+ return (lo >= mid) ? null :
+ new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
+ expectedModCount);
+ }
+
+
+ public void forEachRemaining(Consumer<? super Map.Entry<K, V>> action) {
+ int i, hi, mc;
+ if (action == null)
+ throw new NullPointerException();
+ WeakHashMap<K,V> m = map;
+ WeakHashMap.Entry<K,V>[] tab = m.table;
+ if ((hi = fence) < 0) {
+ mc = expectedModCount = m.modCount;
+ hi = fence = tab.length;
+ }
+ else
+ mc = expectedModCount;
+ if (tab.length >= hi && (i = index) >= 0 &&
+ (i < (index = hi) || current != null)) {
+ WeakHashMap.Entry<K,V> p = current;
+ current = null; // exhaust
+ do {
+ if (p == null)
+ p = tab[i++];
+ else {
+ Object x = p.get();
+ V v = p.value;
+ p = p.next;
+ if (x != null) {
+ @SuppressWarnings("unchecked") K k =
+ (K) WeakHashMap.unmaskNull(x);
+ action.accept
+ (new AbstractMap.SimpleImmutableEntry<>(k, v));
+ }
+ }
+ } while (p != null || i < hi);
+ }
+ if (m.modCount != mc)
+ throw new ConcurrentModificationException();
+ }
+
+ public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
+ int hi;
+ if (action == null)
+ throw new NullPointerException();
+ WeakHashMap.Entry<K,V>[] tab = map.table;
+ if (tab.length >= (hi = getFence()) && index >= 0) {
+ while (current != null || index < hi) {
+ if (current == null)
+ current = tab[index++];
+ else {
+ Object x = current.get();
+ V v = current.value;
+ current = current.next;
+ if (x != null) {
+ @SuppressWarnings("unchecked") K k =
+ (K) WeakHashMap.unmaskNull(x);
+ action.accept
+ (new AbstractMap.SimpleImmutableEntry<>(k, v));
+ if (map.modCount != expectedModCount)
+ throw new ConcurrentModificationException();
+ return true;
+ }
+ }
+ }
+ }
+ return false;
+ }
+
+ public int characteristics() {
+ return Spliterator.DISTINCT;
+ }
+ }
+
+}