package java.util;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
/**
* 1）基于弱引用键实现 Map 接口的哈希表，对于给定的键，当内存紧张时，垃圾回收器会按需回收键值对。
* 2）WeakHashMap 支持 null 键和 null 值
* 3）WeakHashMap 是线程不同步的，可以通过
* {@link Collections#synchronizedMap Collections.synchronizedMap}
* 方法获取线程同步的 Map。
*/
public class WeakHashMap<K,V>
extends AbstractMap<K,V>
implements Map<K,V> {
/**
* The default initial capacity -- MUST be a power of two.
* 默认的初始容量
*/
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.
* 默认的最大大小
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The load factor used when none specified in constructor.
* 默认的加载因子，当未在构造函数中指定时
*/
private static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
* The table, resized as necessary. Length MUST Always be a power of two.
* 哈希表数组
*/
Entry<K,V>[] table;
/**
* The number of key-value mappings contained in this weak hash map.
* 当前总的键值对数目
*/
private int size;
/**
* The next size value at which to resize (capacity * load factor).
* 下一次扩容的阈值
*/
private int threshold;
/**
* The load factor for the hash table.
* WeakHashMap 的加载因子
*/
private final float loadFactor;
/**
* Reference queue for cleared WeakEntries
* 存放被清除条目的引用队列
*/
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.
* WeakHashMap 的结构化修改次数
*/
int modCount;
/**
* 新建 bucket 数为 n 的哈希表
* created by ZXD at 22 Jul 2018 T 13:02:58
*/
@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.
* 基于自定义的初始化容量 initialCapacity 和加载因子 loadFactor 创建 WeakHashMap 实例
*/
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).
* 基于自定义的初始化容量 initialCapacity 和加载因子 0.75 创建 WeakHashMap 实例
*/
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).
* 基于默认的初始化容量 16 和加载因子 0.75 创建 WeakHashMap 实例
*/
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.
* 基于默认的初始化容量 16 和加载因子 0.75 创建 WeakHashMap 实例，并将形参 map 中的条目都
* 加入到 WeakHashMap 中。
*/
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.
* null 键的占位符键
*/
private static final Object NULL_KEY = new Object();
/**
* Use NULL_KEY for key if it is null.
* 将 null 键转换为占位符键
*/
private static Object maskNull(Object key) {
return (key == null) ? NULL_KEY : key;
}
/**
* Returns internal representation of null key back to caller as null.
* 将占位符键转换为 null 键
*/
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.
* 根据哈希码和表长度计算索引值
*/
private static int indexFor(int h, int length) {
return h & (length-1);
}
/**
* Expunges stale entries from the table.
* 从 WeakHashMap 中清除存在于引用队列中的所有键值对
*/
private void expungeStaleEntries() {
// 依次弹出引用队列中的所有条目
for (Object x; (x = queue.poll()) != null; ) {
synchronized (queue) {
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>) x; // 暂存当前键值对
int i = indexFor(e.hash, table.length); // 计算键值对在哈希表中的索引
Entry<K,V> prev = table[i]; // 获取 bucket 的首节点
Entry<K,V> p = prev; // 暂存首节点
while (p != null) {
Entry<K,V> next = p.next; // 获取后置节点
if (p == e) { // 当前节点匹配目标节点
if (prev == e) // 当前节点为首节点
table[i] = next; // 更新 bucket 的首节点为当前节点的后置节点
else
prev.next = next; //
// Must not null out e.next;
// stale entries may be in use by a HashIterator
e.value = null; // Help GC 将目标节点的值置为 null
size--;
break; // 一旦找到则跳出循环
}
prev = p; // 继续遍历下一个节点
p = next;
}
}
}
}
/**
* Returns the table after first expunging stale entries.
* 每次在获取哈希表时，都会执行一次弱键清理
*/
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.
* 执行一次弱键清理，并返回有效的总键值对数目
*/
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.
* 是否为空
*/
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.
* 根据指定的键读取值
*/
public V get(Object key) {
Object k = maskNull(key); // 暂存键
int h = hash(k); // 计算键的哈希值
Entry<K,V>[] tab = getTable(); // 获取哈希表
int index = indexFor(h, tab.length); // 计算索引
Entry<K,V> e = tab[index]; // 获取具体的 bucket
while (e != null) { // 遍历这个 bucket 关联的单向链表，并查找相等的键
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.
* WeakHashMap 中是否包含指定的键
*/
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.
* 根据指定的键获取键值对
*/
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.
* 如果键已经存在，则使用新值替换旧值，并返回旧值；
* 否则插入新的键值对，并返回 null。
*/
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);
// 遍历单向链表
for (Entry<K,V> e = tab[i]; e != null; e = e.next) {
if (h == e.hash && eq(k, e.get())) { // 找到匹配的键值对
V oldValue = e.value; // 暂存旧值
if (value != oldValue) // 旧值和新值不相等，则替换为新值
e.value = value;
return oldValue; // 返回旧值
}
}
modCount++;
Entry<K,V> e = tab[i]; // 获取单向链表首节点
tab[i] = new Entry<>(k, value, queue, h, e); // 将新节点作为 bucket 首节点插入到哈希表中
if (++size >= threshold) // 元素总数超出扩容阈值
resize(tab.length * 2); // 扩容为原来的两倍
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.
* 当哈希表的容量为 1 << 30 时，不进行扩容，而是将阈值设置为 Integer.MAX_VALUE
*/
void resize(int newCapacity) {
Entry<K,V>[] oldTable = getTable(); // 暂存旧哈希表
int oldCapacity = oldTable.length; // 暂存旧容量
if (oldCapacity == MAXIMUM_CAPACITY) { // 如果旧容量达到 MAXIMUM_CAPACITY
threshold = Integer.MAX_VALUE; // 更新扩容阈值为 Integer.MAX_VALUE
return;
}
Entry<K,V>[] newTable = newTable(newCapacity); // 创建新容量的哈希表
transfer(oldTable, newTable); // 迁移数据
table = newTable; // 更新哈希表
/*
* 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.
* 键值对总数大于等于扩容阈值的二分之一
*/
if (size >= threshold / 2) {
// 更新扩容阈值
threshold = (int)(newCapacity * loadFactor);
} else {
// 根据引用队列清除无效的键值对
expungeStaleEntries();
// 回迁数据
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) { // 遍历整个哈希表
Entry<K,V> e = src[j]; // 暂存首节点
src[j] = null; // 将原 bucket 置为 null
while (e != null) { // 如果 bucket 不为 null
Entry<K,V> next = e.next; // 暂存下一个节点
Object key = e.get(); // 读取弱引用的键
if (key == null) { // 键为 null，已经被回收
e.next = null; // Help GC
e.value = null; // " "
size--; // 减小容量
} else { // 键未被回收
// 基于哈希值和新的容量计算 index
int i = indexFor(e.hash, dest.length);
e.next = dest[i]; // 当前节点的后置节点设置为新哈希表的首节点
dest[i] = e; // 新 bucket 的首节点设置为当前节点
}
e = next; // 继续处理下一个节点
}
}
}
/**
* 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.
*/
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.
* 根据指定的键移除条目
*/
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())) { // 找到目标键
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() {
// 清除引用队列
while (queue.poll() != null)
;
modCount++;
Arrays.fill(table, null); // 将哈希表的 bucket 都置为 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.
// 再次清除引用队列
while (queue.poll() != null)
;
}
/**
* Returns {@code true} if this map maps one or more keys to the
* specified value.
* WeakHashMap 是否包含指定的值
*/
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
* 是否包含 null 值
*/
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;
}
}
}
WeakHashMap 源码分析
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