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	/*
	* 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 <tt>Map</tt> interface, with
	* <em>weak keys</em>.
	* An entry in a <tt>WeakHashMap</tt> 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 <tt>Map</tt>
	* implementations.
	*
	* <p> Both null values and the null key are supported. This class has
	* performance characteristics similar to those of the <tt>HashMap</tt>
	* 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 <tt>WeakHashMap</tt> may be constructed using the
	* {@link Collections#synchronizedMap Collections.synchronizedMap}
	* method.
	*
	* <p> This class is intended primarily for use with key objects whose
	* <tt>equals</tt> methods test for object identity using the
	* <tt>==</tt> 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
	* <tt>WeakHashMap</tt> at some later time and be surprised that its entry
	* has been removed. This class will work perfectly well with key objects
	* whose <tt>equals</tt> methods are not based upon object identity, such
	* as <tt>String</tt> instances. With such recreatable key objects,
	* however, the automatic removal of <tt>WeakHashMap</tt> entries whose
	* keys have been discarded may prove to be confusing.
	*
	* <p> The behavior of the <tt>WeakHashMap</tt> class depends in part upon
	* the actions of the garbage collector, so several familiar (though not
	* required) <tt>Map</tt> invariants do not hold for this class. Because
	* the garbage collector may discard keys at any time, a
	* <tt>WeakHashMap</tt> may behave as though an unknown thread is silently
	* removing entries. In particular, even if you synchronize on a
	* <tt>WeakHashMap</tt> instance and invoke none of its mutator methods, it
	* is possible for the <tt>size</tt> method to return smaller values over
	* time, for the <tt>isEmpty</tt> method to return <tt>false</tt> and
	* then <tt>true</tt>, for the <tt>containsKey</tt> method to return
	* <tt>true</tt> and later <tt>false</tt> for a given key, for the
	* <tt>get</tt> method to return a value for a given key but later return
	* <tt>null</tt>, for the <tt>put</tt> method to return
	* <tt>null</tt> and the <tt>remove</tt> method to return
	* <tt>false</tt> 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 <tt>WeakHashMap</tt> 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
	* <tt>WeakHashMap</tt> 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 <tt>WeakHashMap</tt> 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
	* <tt>WeakReferences</tt> before
	* inserting, as in: <tt>m.put(key, new WeakReference(value))</tt>,
	* and then unwrapping upon each <tt>get</tt>.
	*
	* <p>The iterators returned by the <tt>iterator</tt> 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
	* <tt>remove</tt> 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 <tt>ConcurrentModificationException</tt> 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}/../technotes/guides/collections/index.html">
	* 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 <tt>WeakHashMap</tt> with the given initial
	* capacity and the given load factor.
	*
	* @param initialCapacity The initial capacity of the <tt>WeakHashMap</tt>
	* @param loadFactor The load factor of the <tt>WeakHashMap</tt>
	* @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 <tt>WeakHashMap</tt> with the given initial
	* capacity and the default load factor (0.75).
	*
	* @param initialCapacity The initial capacity of the <tt>WeakHashMap</tt>
	* @throws IllegalArgumentException if the initial capacity is negative
	*/
	public WeakHashMap(int initialCapacity) {
	this(initialCapacity, DEFAULT_LOAD_FACTOR);
	}

	/**
	* Constructs a new, empty <tt>WeakHashMap</tt> with the default initial
	* capacity (16) and load factor (0.75).
	*/
	public WeakHashMap() {
	this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
	}

	/**
	* Constructs a new <tt>WeakHashMap</tt> with the same mappings as the
	* specified map. The <tt>WeakHashMap</tt> 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 <tt>true</tt> 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 (key==null ? k==null :
	* key.equals(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 <tt>true</tt> if this map contains a mapping for the
	* specified key.
	*
	* @param key The key whose presence in this map is to be tested
	* @return <tt>true</tt> if there is a mapping for <tt>key</tt>;
	* <tt>false</tt> 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 <tt>key</tt>, or
	* <tt>null</tt> if there was no mapping for <tt>key</tt>.
	* (A <tt>null</tt> return can also indicate that the map
	* previously associated <tt>null</tt> with <tt>key</tt>.)
	*/
	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 <tt>k</tt> to
	* value <tt>v</tt> 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 <tt>null</tt> if the map contained no mapping for the key. A
	* return value of <tt>null</tt> 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 <tt>null</tt>.
	*
	* <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 <tt>key</tt>, or
	* <tt>null</tt> if there was no mapping for <tt>key</tt>
	*/
	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 <tt>true</tt> 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 <tt>true</tt> 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 <tt>remove</tt> operation), the results of
	* the iteration are undefined. The set supports element removal,
	* which removes the corresponding mapping from the map, via the
	* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
	* operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
	* 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 <tt>remove</tt> operation),
	* the results of the iteration are undefined. The collection
	* supports element removal, which removes the corresponding
	* mapping from the map, via the <tt>Iterator.remove</tt>,
	* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
	* <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
	* support the <tt>add</tt> or <tt>addAll</tt> 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 <tt>remove</tt> operation, or through the
	* <tt>setValue</tt> 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 <tt>Iterator.remove</tt>,
	* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
	* <tt>clear</tt> operations. It does not support the
	* <tt>add</tt> or <tt>addAll</tt> 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<K,V>(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<K,V>(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<K,V>(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>(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>(k, v));
	if (map.modCount != expectedModCount)
	throw new ConcurrentModificationException();
	return true;
	}
	}
	}
	}
	return false;
	}

	public int characteristics() {
	return Spliterator.DISTINCT;
	}
	}

	}

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