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;
/**
* 基于Map接口的弱关键字（weak keys）散列表实现。存储的内容也是键值对（key-value）映射，而且键和值都可以是null。
* 当某个关键字不再被引用的时候，WeakHashMap会自动删除该关键字对应的Entry。
* 对于一个给定的键，其映射的存在并不阻止垃圾回收器对该键的丢弃，这就使该键成为可终止的，并被终止，然后被回收。
* 某个键被终止时，它对应的键值对也就从映射中有效移除了。所以这个类的表现行为不同于其他Map接口的实现类。
* WeakHashMap类与HashMap类有类似的字符串性能，同样性能由两个参数影响：初始容量initial capacity和装载因子load factor。
*
* 和HashMap一样，WeakHashMap是不同步的。可以使用Collections.synchronizedMap方法来构造同步的WeakHashMap。
*
* WeakHashMap类最初是用==操作符来调用Key对象的equals函数测试对象相等。
* WeakHashMap对于equals方法不是基于对象相等的关键字对象也能很好的工作，比如String实例。
* 然而，对于这样可重新创建的关键字对象，从WeakHashMap中移除被丢弃的关键字对应的Entry这样的原子操作可能会产生混淆。
* WeakHashMap的行为多少会依赖垃圾收集器的行为，所以一些常用的Map约束并不适用于这个类。因为垃圾收集器会随时丢弃关键字。
* 一个WeakHashMap实例可能表现的好像有一个未知的线程安静地删除Entry。即使是同步synchronized修饰后，也还是会随着时间删除关键字。
*
* WeakHashMap中的关键字对象都是弱键的引用对象。当一个关键字只被弱引用时，不论是Map内部还是外部的弱引用，都会被垃圾收集器自动移除。
* 注意：WeakHashMap的值对象是普通的强引用。要注意不要让值对象强引用到自身的关键字上，直接或间接都不行，这样会阻止关键字的回收。
* 值引用可能会间接引用到WeakHashMap本身的关键字，所以在添加键值对的方式最好是：m.put(key, new WeakReference(value))
* 然后每次get操作之后再拆解掉WeakReference。
*
* iterator返回的迭代器是fail-fast的。
*/
/**
* WeakHashMap继承于AbstractMap，实现了Map接口。WeakHashMap的键是弱键。
* 弱键的原理是通过WeakReference和ReferenceQueue实现的。WeakHashMap的Key是WeakReference类型的。
* ReferenceQueue是一个队列，它会保存被GC回收的弱键。实现步骤是：
* 1）新建WeakHashMap，将键值对添加到WeakHashMap中。实际上，WeakHashMap是通过数组table保存Entry，每个Entry是一个单向键值对链表。
* 2）当某弱键不再被其他对象引用，并被GC回收时，在GC回收该弱键时，这个弱键也同时会被添加到ReferenceQueue（Queue）队列中。
* 3）当下一次需要操作WeakHashMap时，会先同步table和Queue。table中保存了全部的键值对，而Queue中保存了被GC回收的键值对；同步它们，就是删除table中被GC回收的键值对。
* 这就是弱键如何被自动从WeakHashMap中删除的步骤了。
*/
public class WeakHashMap<K,V>
extends AbstractMap<K,V>
implements Map<K,V> {
/**
* 默认初始容量 -- 必须是2的次幂
*/
private static final int DEFAULT_INITIAL_CAPACITY = 16;
/**
* 最大容量，必须是小于1<<30的2的次幂
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* 默认装载因子
*/
private static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
* table数组，必要时会改变大小，但长度必须是2的次幂
*/
Entry<K,V>[] table;
/**
* WeakHashMap中键值对的数目
*/
private int size;
/**
* 更改大小时下一个数组大小（容量*装载因子）
*/
private int threshold;
/**
* 哈希表的装载因子
*/
private final float loadFactor;
/**
* 已经被GC清除的弱引用键值对（WeakEntry）的引用队列
*/
private final ReferenceQueue<Object> queue = new ReferenceQueue<>();
/**
* WeakHashMap的结构更改次数。用于fail-fast
*/
int modCount;
//创建Entry数组table
@SuppressWarnings("unchecked")
private Entry<K,V>[] newTable(int n) {
return (Entry<K,V>[]) new Entry<?,?>[n];
}
/**
* 构造函数1：指定容量大小和加载因子的构造函数
*/
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);
}
/**
* 构造函数2：指定容量大小构造函数，默认装载因子
* @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);
}
/**
* 构造函数3：默认容量和默认装载因子
*/
public WeakHashMap() {
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
}
/**
* 构造函数4：根据指定Map中的键值对构造WeakHashMap，默认装载因子，初始容量为能容纳Map中关键字为准
* @param m the map whose mappings are to be placed in this map
* @throws NullPointerException if the specified map is null
*/
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);
}
// 内部工具函数
/**
* 用于table内部表示空关键字的值对象NULL_KEY
*/
private static final Object NULL_KEY = new Object();
/**
* 如果关键字为null，使用NULL_KEY替换
*/
private static Object maskNull(Object key) {
return (key == null) ? NULL_KEY : key;
}
/**
* 将空关键字的内部表示转换为null
*/
static Object unmaskNull(Object key) {
return (key == NULL_KEY) ? null : key;
}
/**
* 验证非空引用x和可能为空的引用y之间的相等性，默认使用equals方法
*/
private static boolean eq(Object x, Object y) {
return x == y || x.equals(y);
}
/**
* 返回对象的哈希值
*/
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);
}
/**
* 指定哈希值的下标
*/
private static int indexFor(int h, int length) {
return h & (length-1);
}
/**
* 从数组table中移除被丢弃的Entry
* WeakHashMap进行增删改查时，都调用了expungeStaleEntries()方法
*/
private void expungeStaleEntries() {
for (Object x; (x = queue.poll()) != null; ) {
synchronized (queue) {
//e为要清理的对象
@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循环遍历冲突链表
while (p != null) {
Entry<K,V> next = p.next;
if (p == e) {
//如果e为链表第一个Entry
if (prev == e)
table[i] = next;
else
//不是第一个
prev.next = next;
// Must not null out e.next;
// stale entries may be in use by a HashIterator
//这里把value赋值为null，来帮助GC回收强引用的value
e.value = null; //help GC
size--;
break;
}
prev = p;
p = next;
}
}
}
}
/**
* 先移除丢弃的Entry，然后返回数组table
*/
private Entry<K,V>[] getTable() {
expungeStaleEntries();
return table;
}
/**
* 返回Map中键值对的数目。返回之前先调用expungeStaleEntries()方法
*/
public int size() {
if (size == 0)
return 0;
expungeStaleEntries();
return size;
}
/**
* Map中不包含任何键值对时返回true
*/
public boolean isEmpty() {
return size() == 0;
}
/**
* 返回指定关键字的value值，不存在则返回null。
*/
public V get(Object key) {
Object k = maskNull(key);
int h = hash(k);
//getTable中调用了expungeStaleEntries()方法
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()))//关键字的哈希值相同且值对象相等（eq方法返回true）
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);
//getTable方法中调用了expungeStaleEntries()清除掉丢弃的Entry
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;
}
/**
* 将指定值和指定关键字关联起来
* @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);
//getTable中调用了expungeStaleEntries()方法，更新了table数组
Entry<K,V>[] tab = getTable();
int i = indexFor(h, tab.length);
//遍历冲突链，若找到相同Entry，则替换旧值
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;
}
}
//若没有找到相同Entry，在链表开头插入新的Entry
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;
}
/**
* 将Map中的内容重新哈希到新的更大容量的数组中
* 如果当前容量是MAXIMUM_CAPACITY，resize方法不会重新哈希，而是把阈值设置为Integer.MAX_VALUE
* 可以防止之后再调用这个方法
* @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) {
//先调用expungeStaleEntries()删除已被GC清除的弱引用对象
Entry<K,V>[] oldTable = getTable();
int oldCapacity = oldTable.length;
//已经达到最大容量
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;
}
}
/** 将src中所有的Entry移动到dest数组中*/
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());
}
/**
* 如果存在，删除指定关键字对应的Entry对象
* @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.
//清空弱引用队列
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.
//清空完数组后，需要再清空一次引用队列
while (queue.poll() != null)
;
}
/**
* 如果Map中包含指定value值的Entry，返回true
* @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;
}
/**
* 是否包含空值，true为包含
*/
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;
}
/**
* 哈希表中的Entry继承自WeakReference，使用ref字段作为关键字
* WeakHashMap.Entry<K,V>中并没有保存Key，只是将Key与ReferenceQueue关联上了。
*/
private static class Entry<K,V> extends WeakReference<Object> implements Map.Entry<K,V> {
V value;
final int hash;
Entry<K,V> next;
/**
* 创建新的Entry
*/
Entry(Object key, V value,
ReferenceQueue<Object> queue,
int hash, Entry<K,V> next) {
super(key, queue); //指定当前Entry对象的ReferenceQueue
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;
}
//判断对象相等
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 = null;
private Entry<K,V> lastReturned = null;
private int expectedModCount = modCount;
/**
* 为了防止hasNext和next操作之间有关键字消失，这里nextKey是强引用
*/
private Object nextKey = null;
/**
* 强引用，防止在nextEntry和Entry的其他使用阶段发生关键字消失
*/
private Object currentKey = null;
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 = null;
/**
* 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;
return (ks != null ? ks : (keySet = new KeySet()));
}
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;
return (vs != null) ? vs : (values = new Values());
}
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();
}
}
}
}
/**
* 和其他哈希Spliterators类似，只是跳过了已删除元素
*/
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;
}
}
}
