/*
* Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
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*
*
*
*
*
*
*
*/
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;
}
}
}