org.openide.util.WeakSet Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
/*
* @(#)WeakSet.java 0.2 07/02/26
*/
package org.openide.util;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* This class provides storage functionality with Weak-referenced entries and
* new method putIfAbsent. Set implementation is backed by a hash table.
* It also provides method resize for changing capacity of internal hash table
* (can be used for reducing memory occupied by empty set which previously had big number of objects, but they were GCed)
* Access to set is not thread safe.
*
* @param the type of elements maintained by this set
* @see #putIfAbsent(Object)
* @see #resize(int)
* @author Vladimir Voskresensky
*/
@SuppressWarnings("unchecked")
public class WeakSet extends AbstractSet implements Cloneable, Serializable {
private transient SharedKeyWeakHashMap m; // The backing map
private transient Set s; // Its keySet
// Dummy value to associate with an Object in the backing Map
@SuppressWarnings("BooleanConstructorCall")
private static final Object PRESENT = new Boolean(true);
/** load factor */
private final float loadFactor;
/**
* Constructs a new, empty WeakSet with the given initial
* capacity and the given load factor.
*
* @param initialCapacity The initial capacity of the WeakSet
* @param loadFactor The load factor of the WeakSet
* @throws IllegalArgumentException if the initial capacity is negative,
* or if the load factor is nonpositive.
*/
public WeakSet(int initialCapacity, float loadFactor) {
m = new SharedKeyWeakHashMap(initialCapacity, loadFactor);
this.loadFactor = loadFactor;
s = m.keySet();
}
/**
* Constructs a new, empty WeakSet with the given initial
* capacity and the default load factor (0.75).
*
* @param initialCapacity The initial capacity of the WeakSet
* @throws IllegalArgumentException if the initial capacity is negative
*/
public WeakSet(int initialCapacity) {
this(initialCapacity, SharedKeyWeakHashMap.DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new, empty WeakSet with the default initial
* capacity (16) and load factor (0.75).
*/
public WeakSet() {
this(SharedKeyWeakHashMap.DEFAULT_INITIAL_CAPACITY, SharedKeyWeakHashMap.DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new WeakSet with the same mappings as the
* specified map. The WeakSet is created with the default
* load factor (0.75) and an initial capacity sufficient to hold the
* mappings in the specified map.
*
* @param s the map whose mappings are to be placed in this map
* @throws NullPointerException if the specified map is null
*/
public WeakSet(Collection s) {
this(Math.max((int) (s.size() / SharedKeyWeakHashMap.DEFAULT_LOAD_FACTOR) + 1, 16),
SharedKeyWeakHashMap.DEFAULT_LOAD_FACTOR);
addAll(s);
}
@Override
public void clear() { m.clear(); }
@Override
public int size() { return m.size(); }
@Override
public boolean isEmpty() { return m.isEmpty(); }
@Override
@SuppressWarnings("element-type-mismatch")
public boolean contains(Object o) { return m.containsKey(o); }
@Override
@SuppressWarnings("element-type-mismatch")
public boolean remove(Object o) { return m.remove(o) == PRESENT; }
/**
* compact set if it is empty by setting new capacity
* @param newCapacity new capacity
* @since 8.11
*/
public void resize(int newCapacity){
if (isEmpty()) {
m.resize(newCapacity);
}
}
/**
* @see #putIfAbsent
*/
@Override
public boolean add(E e) {
boolean[] modified = { false };
m.putIfAbsent(e, modified);
return modified[0];
}
@Override
public Iterator iterator() { return s.iterator(); }
@Override
public Object[] toArray() { return s.toArray(); }
@Override
public T[] toArray(T[] a) { return s.toArray(a); }
@Override
public String toString() { return s.toString(); }
@Override
public int hashCode() { return s.hashCode(); }
@Override
@SuppressWarnings("EqualsWhichDoesntCheckParameterClass")
public boolean equals(Object o) { return o == this || s.equals(o); }
@Override
public boolean containsAll(Collection c) {return s.containsAll(c);}
@Override
public boolean removeAll(Collection c) {return s.removeAll(c);}
@Override
public boolean retainAll(Collection c) {return s.retainAll(c);}
// addAll is the only inherited implementation
/**
* Put object in this set if equal one is not yet in set.
* Returns previous set entry if equal object is already in set.
*
*
* WeakSet<MyClass> set = new WeakSet<MyClass>();
* ...
* MyClass sharedValue = set.putIfAbsent(new MyClass("abc));
*
*
* @param e object to put in set.
* @return the previous set entry equals with e, or
* passed object e if there were not entry in set.
* @since 8.11
*/
public E putIfAbsent(E e) { return m.putIfAbsent(e, (boolean[]) null); }
private static final long serialVersionUID = 2454657854757543876L;
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeObject(toArray());
}
private void readObject(java.io.ObjectInputStream stream)
throws IOException, ClassNotFoundException {
stream.defaultReadObject();
Object[] arr = (Object[]) stream.readObject();
m = new SharedKeyWeakHashMap(arr.length, loadFactor);
for (Object object : arr) {
m.putIfAbsent((E)object, (boolean[]) null);
}
s = m.keySet();
}
@Override
public Object clone() {
try {
WeakSet nws = (WeakSet) super.clone();
// sharing load factor is ok
// but we can not share maps, recreate them
nws.m = new SharedKeyWeakHashMap(size(), loadFactor);
nws.s = nws.m.keySet();
nws.addAll(this);
return nws;
} catch (CloneNotSupportedException e) {
throw new IllegalStateException("base class doesn't support clone", e); // NOI18N
}
}
// delegate class with only one special method putOrGet
// remove entry value field for performance and memory consumption
// all other is copied from java.util.WeakHashMap
private static final class SharedKeyWeakHashMap
extends AbstractMap
implements Map {
/**
* 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 fast 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.
*/
private Entry[] 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 queue = new ReferenceQueue();
/**
* The number of times this SharedKeyWeakHashMap 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
*/
private volatile int modCount;
/**
* Constructs a new, empty SharedKeyWeakHashMap with the given initial
* capacity and the given load factor.
*
* @param initialCapacity The initial capacity of the SharedKeyWeakHashMap
* @param loadFactor The load factor of the SharedKeyWeakHashMap
* @throws IllegalArgumentException if the initial capacity is negative,
* or if the load factor is nonpositive.
*/
public SharedKeyWeakHashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0) {
throw new IllegalArgumentException("Illegal Initial Capacity: "+ // NOI18N
initialCapacity);
}
if (initialCapacity > MAXIMUM_CAPACITY) {
initialCapacity = MAXIMUM_CAPACITY;
}
if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
throw new IllegalArgumentException("Illegal Load factor: "+ // NOI18N
loadFactor);
}
int capacity = 1;
while (capacity < initialCapacity) {
capacity <<= 1;
}
table = (Entry[])new Entry[capacity];
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
}
/**
* Constructs a new, empty SharedKeyWeakHashMap with the given initial
* capacity and the default load factor (0.75).
*
* @param initialCapacity The initial capacity of the SharedKeyWeakHashMap
* @throws IllegalArgumentException if the initial capacity is negative
*/
public SharedKeyWeakHashMap(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs a new, empty SharedKeyWeakHashMap with the default initial
* capacity (16) and load factor (0.75).
*/
public SharedKeyWeakHashMap() {
this.loadFactor = DEFAULT_LOAD_FACTOR;
threshold = DEFAULT_INITIAL_CAPACITY;
table = new Entry[DEFAULT_INITIAL_CAPACITY];
}
/**
* Constructs a new SharedKeyWeakHashMap with the same mappings as the
* specified map. The SharedKeyWeakHashMap 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 SharedKeyWeakHashMap(Map m) {
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1, 16),
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.
*/
private static K unmaskNull(Object key) {
return (K) (key == NULL_KEY ? null : key);
}
/**
* Checks for equality of non-null reference x and possibly-null y. By
* default uses Object.equals.
*/
static boolean eq(Object x, Object y) {
return x == y || x.equals(y);
}
/**
* Returns index for hash code h.
*/
static int indexFor(int h, int length) {
return h & (length-1);
}
/**
* Expunges stale entries from the table.
*/
private void expungeStaleEntries() {
Entry e;
while ( (e = (Entry) queue.poll()) != null) {
int h = e.hash;
int i = indexFor(h, table.length);
Entry prev = table[i];
Entry p = prev;
while (p != null) {
Entry next = p.next;
if (p == e) {
if (prev == e) {
table[i] = next;
}
else {
prev.next = next;
}
e.next = null; // Help GC
//e.value = null; // " "
size--;
break;
}
prev = p;
p = next;
}
}
}
/**
* Returns the table after first expunging stale entries.
*/
@SuppressWarnings("ReturnOfCollectionOrArrayField")
private Entry[] 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.
*/
@Override
public int size() {
if (size == 0) {
return 0;
}
expungeStaleEntries();
return size;
}
/**
* Returns 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.
*/
@Override
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.
*
* 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.)
*
*
A return value of {@code null} does not necessarily
* 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)
*/
@Override
public V get(Object key) {
throw new UnsupportedOperationException();
}
/**
* Returns true if this map contains a mapping for the
* specified key.
*
* @param key The key whose presence in this map is to be tested
* @return true if there is a mapping for key;
* false otherwise
*/
@Override
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 getEntry(Object key) {
Object k = maskNull(key);
int h = hash(k.hashCode());
Entry[] tab = getTable();
int index = indexFor(h, tab.length);
Entry 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 key, or
* null if there was no mapping for key.
* (A null return can also indicate that the map
* previously associated null with key.)
*/
@Override
public V put(K key, V value) {
throw new UnsupportedOperationException("use putIfAbsent instead"); // NOI18N
}
/**
* 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[] oldTable = getTable();
int oldCapacity = oldTable.length;
if (oldCapacity == MAXIMUM_CAPACITY) {
threshold = Integer.MAX_VALUE;
return;
}
Entry[] newTable = new Entry[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[] src, Entry[] dest) {
for (int j = 0; j < src.length; ++j) {
Entry e = src[j];
src[j] = null;
while (e != null) {
Entry next = e.next;
Object key = e.get();
if (key == null) {
e.next = null; // Help GC
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.
*/
@Override
public void putAll(Map 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 e : m.entrySet()) {
putIfAbsent(e.getKey(), (boolean[]) null);
}
}
/**
* 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 k to
* value v such that (key==null ? k==null :
* key.equals(k)), that mapping is removed. (The map can contain
* at most one such mapping.)
*
* Returns the value to which this map previously associated the key,
* or null if the map contained no mapping for the key. A
* return value of null does not necessarily indicate
* that the map contained no mapping for the key; it's also possible
* that the map explicitly mapped the key to null.
*
*
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 key, or
* null if there was no mapping for key
*/
@Override
public V remove(Object key) {
Object k = maskNull(key);
int h = hash(k.hashCode());
Entry[] tab = getTable();
int i = indexFor(h, tab.length);
Entry prev = tab[i];
Entry e = prev;
while (e != null) {
Entry next = e.next;
if (h == e.hash && eq(k, e.get())) {
modCount++;
size--;
if (prev == e) {
tab[i] = next;
} else {
prev.next = next;
}
return (V)PRESENT;
}
prev = e;
e = next;
}
return null;
}
/** Special version of remove needed by Entry set */
Entry removeMapping(Object o) {
if (!(o instanceof Map.Entry)) {
return null;
}
Entry[] tab = getTable();
Map.Entry entry = (Map.Entry)o;
Object k = maskNull(entry.getKey());
int h = hash(k.hashCode());
int i = indexFor(h, tab.length);
Entry prev = tab[i];
Entry e = prev;
while (e != null) {
Entry next = e.next;
if (h == e.hash && e.equals(entry)) {
modCount++;
size--;
if (prev == e) {
tab[i] = next;
} else {
prev.next = next;
}
return e;
}
prev = e;
e = next;
}
return null;
}
/**
* Removes all of the mappings from this map.
* The map will be empty after this call returns.
*/
@Override
public void clear() {
// clear out ref queue. We don't need to expunge entries
// since table is getting cleared.
while (queue.poll() != null) {}
modCount++;
Entry[] tab = table;
for (int i = 0; i < tab.length; ++i) {
tab[i] = 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 true if this map maps one or more keys to the
* specified value.
*
* @param value value whose presence in this map is to be tested
* @return true if this map maps one or more keys to the
* specified value
*/
@Override
public boolean containsValue(Object value) {
if (value==null) {
return containsNullValue();
}
return false;
}
/**
* Special-case code for containsValue with null argument
*/
private boolean containsNullValue() {
Entry[] tab = getTable();
for (int i = tab.length ; i-- > 0 ;) {
for (Entry e = tab[i] ; e != null ; e = e.next) {
return true;
}
}
return false;
}
/**
* The entries in this hash table extend WeakReference, using its main ref
* field as the key.
*/
private static final class Entry extends WeakReference implements Map.Entry {
private final int hash;
private Entry next;
/**
* Creates new entry.
*/
Entry(K key,
ReferenceQueue queue,
int hash, Entry next) {
super(key, queue);
this.hash = hash;
this.next = next;
}
@Override
public K getKey() {
return SharedKeyWeakHashMap.unmaskNull(get());
}
@Override
public V getValue() {
return null;
}
@Override
public V setValue(V newValue) {
return null;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry e = (Map.Entry)o;
Object k1 = getKey();
Object k2 = e.getKey();
if (k1 == k2 || (k1 != null && k1.equals(k2))) {
return true;
}
return false;
}
@Override
public int hashCode() {
Object k = getKey();
return (k==null ? 0 : k.hashCode());
}
@Override
public String toString() {
return "" + getKey(); // NOI18N
}
}
/**
* Have to copy AbstractMap.SimpleEntry to eliminate unused fields (i.e. value)
*/
private static final class SimpleEntry
implements Map.Entry, java.io.Serializable {
private static final long serialVersionUID = -8499721149061103585L;
private final K key;
/**
* Creates an entry representing a mapping from the specified
* key to the specified value.
*
* @param key the key represented by this entry
* @param value the value represented by this entry
*/
public SimpleEntry(K key) {
this.key = key;
}
/**
* Creates an entry representing the same mapping as the
* specified entry.
*
* @param entry the entry to copy
*/
public SimpleEntry(Map.Entry entry) {
this.key = entry.getKey();
}
/**
* Returns the key corresponding to this entry.
*
* @return the key corresponding to this entry
*/
@Override
public K getKey() {
return key;
}
/**
* Returns the value corresponding to this entry.
*
* @return the value corresponding to this entry
*/
@Override
public V getValue() {
return null;
}
/**
* Replaces the value corresponding to this entry with the specified
* value.
*
* @param value new value to be stored in this entry
* @return the old value corresponding to the entry
*/
@Override
public V setValue(V value) {
return null;
}
/**
* Compares the specified object with this entry for equality.
* Returns {@code true} if the given object is also a map entry and
* the two entries represent the same mapping. More formally, two
* entries {@code e1} and {@code e2} represent the same mapping
* if
* (e1.getKey()==null ?
* e2.getKey()==null :
* e1.getKey().equals(e2.getKey()))
* This ensures that the {@code equals} method works properly across
* different implementations of the {@code Map.Entry} interface.
*
* @param o object to be compared for equality with this map entry
* @return {@code true} if the specified object is equal to this map
* entry
* @see #hashCode
*/
@Override
public boolean equals(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry e = (Map.Entry)o;
return eq(key, e.getKey());
}
/**
* Returns the hash code value for this map entry. The hash code
* of a map entry {@code e} is defined to be:
* (e.getKey()==null ? 0 : e.getKey().hashCode())
* This ensures that {@code e1.equals(e2)} implies that
* {@code e1.hashCode()==e2.hashCode()} for any two Entries
* {@code e1} and {@code e2}, as required by the general
* contract of {@link Object#hashCode}.
*
* @return the hash code value for this map entry
* @see #equals
*/
@Override
public int hashCode() {
return (key == null ? 0 : key.hashCode());
}
/**
* Returns a String representation of this map entry. This
* implementation returns the string representation of this
* entry's key followed by the equals character ("=")
* followed by the string representation of this entry's value.
*
* @return a String representation of this map entry
*/
@Override
public String toString() {
return "" + key; // NOI18N
}
}
private abstract class HashIterator implements Iterator {
private int index;
private Entry entry = null;
private Entry lastReturned = null;
private int expectedModCount = modCount;
/**
* Strong reference needed to avoid disappearance of key
* between hasNext and next
*/
private Object nextKey = null;
/**
* Strong reference needed to avoid disappearance of key
* between nextEntry() and any use of the entry
*/
private Object currentKey = null;
HashIterator() {
index = (size() != 0 ? table.length : 0);
}
@Override
public boolean hasNext() {
Entry[] t = table;
while (nextKey == null) {
Entry 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 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;
}
@Override
@SuppressWarnings("element-type-mismatch")
public void remove() {
if (lastReturned == null) {
throw new IllegalStateException();
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
SharedKeyWeakHashMap.this.remove(currentKey);
expectedModCount = modCount;
lastReturned = null;
currentKey = null;
}
}
private final class ValueIterator extends HashIterator {
@Override
public V next() {
nextEntry();
return null;
}
}
private final class KeyIterator extends HashIterator {
@Override
public K next() {
return nextEntry().getKey();
}
}
private final class EntryIterator extends HashIterator> {
@Override
public Map.Entry next() {
return nextEntry();
}
}
// Views
private transient Set> 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 remove operation), the results of
* the iteration are undefined. The set supports element removal,
* which removes the corresponding mapping from the map, via the
* Iterator.remove, Set.remove,
* removeAll, retainAll, and clear
* operations. It does not support the add or addAll
* operations.
*/
@Override
public Set keySet() {
Set ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}
private final class KeySet extends AbstractSet {
@Override
public Iterator iterator() {
return new KeyIterator();
}
@Override
public int size() {
return SharedKeyWeakHashMap.this.size();
}
@Override
@SuppressWarnings("element-type-mismatch")
public boolean contains(Object o) {
return containsKey(o);
}
@Override
@SuppressWarnings("element-type-mismatch")
public boolean remove(Object o) {
if (containsKey(o)) {
SharedKeyWeakHashMap.this.remove(o);
return true;
} else {
return false;
}
}
@Override
public void clear() {
SharedKeyWeakHashMap.this.clear();
}
}
/**
* 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 remove operation),
* the results of the iteration are undefined. The collection
* supports element removal, which removes the corresponding
* mapping from the map, via the Iterator.remove,
* Collection.remove, removeAll,
* retainAll and clear operations. It does not
* support the add or addAll operations.
*/
@Override
public Collection values() {
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
private final class Values extends AbstractCollection {
@Override
public Iterator iterator() {
return new ValueIterator();
}
@Override
public int size() {
return SharedKeyWeakHashMap.this.size();
}
@Override
@SuppressWarnings("element-type-mismatch")
public boolean contains(Object o) {
return containsValue(o);
}
@Override
public void clear() {
SharedKeyWeakHashMap.this.clear();
}
}
/**
* 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 remove operation, or through the
* 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 Iterator.remove,
* Set.remove, removeAll, retainAll and
* clear operations. It does not support the
* add or addAll operations.
*/
@Override
public Set> entrySet() {
Set> es = entrySet;
return es != null ? es : (entrySet = new EntrySet());
}
private final class EntrySet extends AbstractSet> {
@Override
public Iterator> iterator() {
return new EntryIterator();
}
@Override
public boolean contains(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry e = (Map.Entry)o;
Entry candidate = getEntry(e.getKey());
return candidate != null && candidate.equals(e);
}
@Override
public boolean remove(Object o) {
return removeMapping(o) != null;
}
@Override
public int size() {
return SharedKeyWeakHashMap.this.size();
}
@Override
public void clear() {
SharedKeyWeakHashMap.this.clear();
}
private List> deepCopy() {
List> list = new ArrayList>(size());
for (Map.Entry e : this) {
list.add(new SimpleEntry(e));
}
return list;
}
@Override
public Object[] toArray() {
return deepCopy().toArray();
}
@Override
public T[] toArray(T[] a) {
return deepCopy().toArray(a);
}
}
////////////////////////////////////////////////////////////////////////////
// new changes
/**
* Applies a supplemental hash function to a given hashCode, 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. Note: Null keys always map to hash 0, thus index 0.
*/
static int hash(int h) {
// 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);
}
// Views
/**
* Each of these fields are initialized to contain an instance of the
* appropriate view the first time this view is requested. The views are
* stateless, so there's no reason to create more than one of each.
*/
private transient volatile Set keySet = null;
private transient volatile Collection values = null;
/**
* Put specified key in this set if key is not yet in set.
* returns previous value in set if key already in set.
*
* @param key key to put in set.
* @param modified array of size one that shall be set if the map is modified or null
* @return the previous set entry equals with key, or
* new key if there were not entry in set.
*/
private K putIfAbsent(K key, boolean[] modified) {
K k = (K) maskNull(key);
int h = hash(k.hashCode());
Entry[] tab = getTable();
int i = indexFor(h, tab.length);
Entry e = tab[i];
while (e != null) {
if (e.hash == h) {
K refedKey = e.get();
if (eq(k, refedKey)) {
return (K)unmaskNull(refedKey);
}
}
e = e.next;
}
modCount++;
e = tab[i];
tab[i] = new Entry(k, queue, h, e);
if (++size >= threshold) {
resize(tab.length * 2);
}
if (modified != null) {
modified[0] = true;
}
return (K)unmaskNull(k);
}
}
}