/*
* 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.
*/
package java.util;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamField;
import java.io.Serializable;
import libcore.util.Objects;
/**
* HashMap is an implementation of {@link Map}. All optional operations are supported.
*
* <p>All elements are permitted as keys or values, including null.
*
* <p>Note that the iteration order for HashMap is non-deterministic. If you want
* deterministic iteration, use {@link LinkedHashMap}.
*
* <p>Note: the implementation of {@code HashMap} is not synchronized.
* If one thread of several threads accessing an instance modifies the map
* structurally, access to the map needs to be synchronized. A structural
* modification is an operation that adds or removes an entry. Changes in
* the value of an entry are not structural changes.
*
* <p>The {@code Iterator} created by calling the {@code iterator} method
* may throw a {@code ConcurrentModificationException} if the map is structurally
* changed while an iterator is used to iterate over the elements. Only the
* {@code remove} method that is provided by the iterator allows for removal of
* elements during iteration. It is not possible to guarantee that this
* mechanism works in all cases of unsynchronized concurrent modification. It
* should only be used for debugging purposes.
*
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*/
public class HashMap<K, V> extends AbstractMap<K, V> implements Cloneable, Serializable {
/**
* Min capacity (other than zero) for a HashMap. Must be a power of two
* greater than 1 (and less than 1 << 30).
*/
private static final int MINIMUM_CAPACITY = 4;
/**
* Max capacity for a HashMap. Must be a power of two >= MINIMUM_CAPACITY.
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* An empty table shared by all zero-capacity maps (typically from default
* constructor). It is never written to, and replaced on first put. Its size
* is set to half the minimum, so that the first resize will create a
* minimum-sized table.
*/
private static final Entry[] EMPTY_TABLE
= new HashMapEntry[MINIMUM_CAPACITY >>> 1];
/**
* The default load factor. Note that this implementation ignores the
* load factor, but cannot do away with it entirely because it's
* mentioned in the API.
*
* <p>Note that this constant has no impact on the behavior of the program,
* but it is emitted as part of the serialized form. The load factor of
* .75 is hardwired into the program, which uses cheap shifts in place of
* expensive division.
*/
static final float DEFAULT_LOAD_FACTOR = .75F;
/**
* The hash table. If this hash map contains a mapping for null, it is
* not represented this hash table.
*/
transient HashMapEntry<K, V>[] table;
/**
* The entry representing the null key, or null if there's no such mapping.
*/
transient HashMapEntry<K, V> entryForNullKey;
/**
* The number of mappings in this hash map.
*/
transient int size;
/**
* Incremented by "structural modifications" to allow (best effort)
* detection of concurrent modification.
*/
transient int modCount;
/**
* The table is rehashed when its size exceeds this threshold.
* The value of this field is generally .75 * capacity, except when
* the capacity is zero, as described in the EMPTY_TABLE declaration
* above.
*/
private transient int threshold;
// Views - lazily initialized
private transient Set<K> keySet;
private transient Set<Entry<K, V>> entrySet;
private transient Collection<V> values;
/**
* Constructs a new empty {@code HashMap} instance.
*/
@SuppressWarnings("unchecked")
public HashMap() {
table = (HashMapEntry<K, V>[]) EMPTY_TABLE;
threshold = -1; // Forces first put invocation to replace EMPTY_TABLE
}
/**
* Constructs a new {@code HashMap} instance with the specified capacity.
*
* @param capacity
* the initial capacity of this hash map.
* @throws IllegalArgumentException
* when the capacity is less than zero.
*/
public HashMap(int capacity) {
if (capacity < 0) {
throw new IllegalArgumentException("Capacity: " + capacity);
}
if (capacity == 0) {
@SuppressWarnings("unchecked")
HashMapEntry<K, V>[] tab = (HashMapEntry<K, V>[]) EMPTY_TABLE;
table = tab;
threshold = -1; // Forces first put() to replace EMPTY_TABLE
return;
}
if (capacity < MINIMUM_CAPACITY) {
capacity = MINIMUM_CAPACITY;
} else if (capacity > MAXIMUM_CAPACITY) {
capacity = MAXIMUM_CAPACITY;
} else {
capacity = roundUpToPowerOfTwo(capacity);
}
makeTable(capacity);
}
/**
* Constructs a new {@code HashMap} instance with the specified capacity and
* load factor.
*
* @param capacity
* the initial capacity of this hash map.
* @param loadFactor
* the initial load factor.
* @throws IllegalArgumentException
* when the capacity is less than zero or the load factor is
* less or equal to zero or NaN.
*/
public HashMap(int capacity, float loadFactor) {
this(capacity);
if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
throw new IllegalArgumentException("Load factor: " + loadFactor);
}
/*
* Note that this implementation ignores loadFactor; it always uses
* a load factor of 3/4. This simplifies the code and generally
* improves performance.
*/
}
/**
* Constructs a new {@code HashMap} instance containing the mappings from
* the specified map.
*
* @param map
* the mappings to add.
*/
public HashMap(Map<? extends K, ? extends V> map) {
this(capacityForInitSize(map.size()));
constructorPutAll(map);
}
/**
* Inserts all of the elements of map into this HashMap in a manner
* suitable for use by constructors and pseudo-constructors (i.e., clone,
* readObject). Also used by LinkedHashMap.
*/
final void constructorPutAll(Map<? extends K, ? extends V> map) {
for (Entry<? extends K, ? extends V> e : map.entrySet()) {
constructorPut(e.getKey(), e.getValue());
}
}
/**
* Returns an appropriate capacity for the specified initial size. Does
* not round the result up to a power of two; the caller must do this!
* The returned value will be between 0 and MAXIMUM_CAPACITY (inclusive).
*/
static int capacityForInitSize(int size) {
int result = (size >> 1) + size; // Multiply by 3/2 to allow for growth
// boolean expr is equivalent to result >= 0 && result<MAXIMUM_CAPACITY
return (result & ~(MAXIMUM_CAPACITY-1))==0 ? result : MAXIMUM_CAPACITY;
}
/**
* Returns a shallow copy of this map.
*
* @return a shallow copy of this map.
*/
@SuppressWarnings("unchecked")
@Override public Object clone() {
/*
* This could be made more efficient. It unnecessarily hashes all of
* the elements in the map.
*/
HashMap<K, V> result;
try {
result = (HashMap<K, V>) super.clone();
} catch (CloneNotSupportedException e) {
throw new AssertionError(e);
}
// Restore clone to empty state, retaining our capacity and threshold
result.makeTable(table.length);
result.entryForNullKey = null;
result.size = 0;
result.keySet = null;
result.entrySet = null;
result.values = null;
result.init(); // Give subclass a chance to initialize itself
result.constructorPutAll(this); // Calls method overridden in subclass!!
return result;
}
/**
* This method is called from the pseudo-constructors (clone and readObject)
* prior to invoking constructorPut/constructorPutAll, which invoke the
* overridden constructorNewEntry method. Normally it is a VERY bad idea to
* invoke an overridden method from a pseudo-constructor (Effective Java
* Item 17). In this case it is unavoidable, and the init method provides a
* workaround.
*/
void init() { }
/**
* Returns whether this map is empty.
*
* @return {@code true} if this map has no elements, {@code false}
* otherwise.
* @see #size()
*/
@Override public boolean isEmpty() {
return size == 0;
}
/**
* Returns the number of elements in this map.
*
* @return the number of elements in this map.
*/
@Override public int size() {
return size;
}
/**
* Returns the value of the mapping with the specified key.
*
* @param key
* the key.
* @return the value of the mapping with the specified key, or {@code null}
* if no mapping for the specified key is found.
*/
public V get(Object key) {
if (key == null) {
HashMapEntry<K, V> e = entryForNullKey;
return e == null ? null : e.value;
}
// Doug Lea's supplemental secondaryHash function (inlined)
int hash = key.hashCode();
hash ^= (hash >>> 20) ^ (hash >>> 12);
hash ^= (hash >>> 7) ^ (hash >>> 4);
HashMapEntry<K, V>[] tab = table;
for (HashMapEntry<K, V> e = tab[hash & (tab.length - 1)];
e != null; e = e.next) {
K eKey = e.key;
if (eKey == key || (e.hash == hash && key.equals(eKey))) {
return e.value;
}
}
return null;
}
/**
* Returns whether this map contains the specified key.
*
* @param key
* the key to search for.
* @return {@code true} if this map contains the specified key,
* {@code false} otherwise.
*/
@Override public boolean containsKey(Object key) {
if (key == null) {
return entryForNullKey != null;
}
// Doug Lea's supplemental secondaryHash function (inlined)
int hash = key.hashCode();
hash ^= (hash >>> 20) ^ (hash >>> 12);
hash ^= (hash >>> 7) ^ (hash >>> 4);
HashMapEntry<K, V>[] tab = table;
for (HashMapEntry<K, V> e = tab[hash & (tab.length - 1)];
e != null; e = e.next) {
K eKey = e.key;
if (eKey == key || (e.hash == hash && key.equals(eKey))) {
return true;
}
}
return false;
}
/**
* Returns whether this map contains the specified value.
*
* @param value
* the value to search for.
* @return {@code true} if this map contains the specified value,
* {@code false} otherwise.
*/
@Override public boolean containsValue(Object value) {
HashMapEntry[] tab = table;
int len = tab.length;
if (value == null) {
for (int i = 0; i < len; i++) {
for (HashMapEntry e = tab[i]; e != null; e = e.next) {
if (e.value == null) {
return true;
}
}
}
return entryForNullKey != null && entryForNullKey.value == null;
}
// value is non-null
for (int i = 0; i < len; i++) {
for (HashMapEntry e = tab[i]; e != null; e = e.next) {
if (value.equals(e.value)) {
return true;
}
}
}
return entryForNullKey != null && value.equals(entryForNullKey.value);
}
/**
* Maps the specified key to the specified value.
*
* @param key
* the key.
* @param value
* the value.
* @return the value of any previous mapping with the specified key or
* {@code null} if there was no such mapping.
*/
@Override public V put(K key, V value) {
if (key == null) {
return putValueForNullKey(value);
}
int hash = secondaryHash(key.hashCode());
HashMapEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
for (HashMapEntry<K, V> e = tab[index]; e != null; e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
preModify(e);
V oldValue = e.value;
e.value = value;
return oldValue;
}
}
// No entry for (non-null) key is present; create one
modCount++;
if (size++ > threshold) {
tab = doubleCapacity();
index = hash & (tab.length - 1);
}
addNewEntry(key, value, hash, index);
return null;
}
private V putValueForNullKey(V value) {
HashMapEntry<K, V> entry = entryForNullKey;
if (entry == null) {
addNewEntryForNullKey(value);
size++;
modCount++;
return null;
} else {
preModify(entry);
V oldValue = entry.value;
entry.value = value;
return oldValue;
}
}
/**
* Give LinkedHashMap a chance to take action when we modify an existing
* entry.
*
* @param e the entry we're about to modify.
*/
void preModify(HashMapEntry<K, V> e) { }
/**
* This method is just like put, except that it doesn't do things that
* are inappropriate or unnecessary for constructors and pseudo-constructors
* (i.e., clone, readObject). In particular, this method does not check to
* ensure that capacity is sufficient, and does not increment modCount.
*/
private void constructorPut(K key, V value) {
if (key == null) {
HashMapEntry<K, V> entry = entryForNullKey;
if (entry == null) {
entryForNullKey = constructorNewEntry(null, value, 0, null);
size++;
} else {
entry.value = value;
}
return;
}
int hash = secondaryHash(key.hashCode());
HashMapEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
HashMapEntry<K, V> first = tab[index];
for (HashMapEntry<K, V> e = first; e != null; e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
e.value = value;
return;
}
}
// No entry for (non-null) key is present; create one
tab[index] = constructorNewEntry(key, value, hash, first);
size++;
}
/**
* Creates a new entry for the given key, value, hash, and index and
* inserts it into the hash table. This method is called by put
* (and indirectly, putAll), and overridden by LinkedHashMap. The hash
* must incorporate the secondary hash function.
*/
void addNewEntry(K key, V value, int hash, int index) {
table[index] = new HashMapEntry<K, V>(key, value, hash, table[index]);
}
/**
* Creates a new entry for the null key, and the given value and
* inserts it into the hash table. This method is called by put
* (and indirectly, putAll), and overridden by LinkedHashMap.
*/
void addNewEntryForNullKey(V value) {
entryForNullKey = new HashMapEntry<K, V>(null, value, 0, null);
}
/**
* Like newEntry, but does not perform any activity that would be
* unnecessary or inappropriate for constructors. In this class, the
* two methods behave identically; in LinkedHashMap, they differ.
*/
HashMapEntry<K, V> constructorNewEntry(
K key, V value, int hash, HashMapEntry<K, V> first) {
return new HashMapEntry<K, V>(key, value, hash, first);
}
/**
* Copies all the mappings in the specified map to this map. These mappings
* will replace all mappings that this map had for any of the keys currently
* in the given map.
*
* @param map
* the map to copy mappings from.
*/
@Override public void putAll(Map<? extends K, ? extends V> map) {
ensureCapacity(map.size());
super.putAll(map);
}
/**
* Ensures that the hash table has sufficient capacity to store the
* specified number of mappings, with room to grow. If not, it increases the
* capacity as appropriate. Like doubleCapacity, this method moves existing
* entries to new buckets as appropriate. Unlike doubleCapacity, this method
* can grow the table by factors of 2^n for n > 1. Hopefully, a single call
* to this method will be faster than multiple calls to doubleCapacity.
*
* <p>This method is called only by putAll.
*/
private void ensureCapacity(int numMappings) {
int newCapacity = roundUpToPowerOfTwo(capacityForInitSize(numMappings));
HashMapEntry<K, V>[] oldTable = table;
int oldCapacity = oldTable.length;
if (newCapacity <= oldCapacity) {
return;
}
if (newCapacity == oldCapacity * 2) {
doubleCapacity();
return;
}
// We're growing by at least 4x, rehash in the obvious way
HashMapEntry<K, V>[] newTable = makeTable(newCapacity);
if (size != 0) {
int newMask = newCapacity - 1;
for (int i = 0; i < oldCapacity; i++) {
for (HashMapEntry<K, V> e = oldTable[i]; e != null;) {
HashMapEntry<K, V> oldNext = e.next;
int newIndex = e.hash & newMask;
HashMapEntry<K, V> newNext = newTable[newIndex];
newTable[newIndex] = e;
e.next = newNext;
e = oldNext;
}
}
}
}
/**
* Allocate a table of the given capacity and set the threshold accordingly.
* @param newCapacity must be a power of two
*/
private HashMapEntry<K, V>[] makeTable(int newCapacity) {
@SuppressWarnings("unchecked") HashMapEntry<K, V>[] newTable
= (HashMapEntry<K, V>[]) new HashMapEntry[newCapacity];
table = newTable;
threshold = (newCapacity >> 1) + (newCapacity >> 2); // 3/4 capacity
return newTable;
}
/**
* Doubles the capacity of the hash table. Existing entries are placed in
* the correct bucket on the enlarged table. If the current capacity is,
* MAXIMUM_CAPACITY, this method is a no-op. Returns the table, which
* will be new unless we were already at MAXIMUM_CAPACITY.
*/
private HashMapEntry<K, V>[] doubleCapacity() {
HashMapEntry<K, V>[] oldTable = table;
int oldCapacity = oldTable.length;
if (oldCapacity == MAXIMUM_CAPACITY) {
return oldTable;
}
int newCapacity = oldCapacity * 2;
HashMapEntry<K, V>[] newTable = makeTable(newCapacity);
if (size == 0) {
return newTable;
}
for (int j = 0; j < oldCapacity; j++) {
/*
* Rehash the bucket using the minimum number of field writes.
* This is the most subtle and delicate code in the class.
*/
HashMapEntry<K, V> e = oldTable[j];
if (e == null) {
continue;
}
int highBit = e.hash & oldCapacity;
HashMapEntry<K, V> broken = null;
newTable[j | highBit] = e;
for (HashMapEntry<K, V> n = e.next; n != null; e = n, n = n.next) {
int nextHighBit = n.hash & oldCapacity;
if (nextHighBit != highBit) {
if (broken == null)
newTable[j | nextHighBit] = n;
else
broken.next = n;
broken = e;
highBit = nextHighBit;
}
}
if (broken != null)
broken.next = null;
}
return newTable;
}
/**
* Removes the mapping with the specified key from this map.
*
* @param key
* the key of the mapping to remove.
* @return the value of the removed mapping or {@code null} if no mapping
* for the specified key was found.
*/
@Override public V remove(Object key) {
if (key == null) {
return removeNullKey();
}
int hash = secondaryHash(key.hashCode());
HashMapEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
for (HashMapEntry<K, V> e = tab[index], prev = null;
e != null; prev = e, e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
if (prev == null) {
tab[index] = e.next;
} else {
prev.next = e.next;
}
modCount++;
size--;
postRemove(e);
return e.value;
}
}
return null;
}
private V removeNullKey() {
HashMapEntry<K, V> e = entryForNullKey;
if (e == null) {
return null;
}
entryForNullKey = null;
modCount++;
size--;
postRemove(e);
return e.value;
}
/**
* Subclass overrides this method to unlink entry.
*/
void postRemove(HashMapEntry<K, V> e) { }
/**
* Removes all mappings from this hash map, leaving it empty.
*
* @see #isEmpty
* @see #size
*/
@Override public void clear() {
if (size != 0) {
Arrays.fill(table, null);
entryForNullKey = null;
modCount++;
size = 0;
}
}
/**
* Returns a set of the keys contained in this map. The set is backed by
* this map so changes to one are reflected by the other. The set does not
* support adding.
*
* @return a set of the keys.
*/
@Override public Set<K> keySet() {
Set<K> ks = keySet;
return (ks != null) ? ks : (keySet = new KeySet());
}
/**
* Returns a collection of the values contained in this map. The collection
* is backed by this map so changes to one are reflected by the other. The
* collection supports remove, removeAll, retainAll and clear operations,
* and it does not support add or addAll operations.
* <p>
* This method returns a collection which is the subclass of
* AbstractCollection. The iterator method of this subclass returns a
* "wrapper object" over the iterator of map's entrySet(). The {@code size}
* method wraps the map's size method and the {@code contains} method wraps
* the map's containsValue method.
* </p>
* <p>
* The collection is created when this method is called for the first time
* and returned in response to all subsequent calls. This method may return
* different collections when multiple concurrent calls occur, since no
* synchronization is performed.
* </p>
*
* @return a collection of the values contained in this map.
*/
@Override public Collection<V> values() {
Collection<V> vs = values;
return (vs != null) ? vs : (values = new Values());
}
/**
* Returns a set containing all of the mappings in this map. Each mapping is
* an instance of {@link Map.Entry}. As the set is backed by this map,
* changes in one will be reflected in the other.
*
* @return a set of the mappings.
*/
public Set<Entry<K, V>> entrySet() {
Set<Entry<K, V>> es = entrySet;
return (es != null) ? es : (entrySet = new EntrySet());
}
static class HashMapEntry<K, V> implements Entry<K, V> {
final K key;
V value;
final int hash;
HashMapEntry<K, V> next;
HashMapEntry(K key, V value, int hash, HashMapEntry<K, V> next) {
this.key = key;
this.value = value;
this.hash = hash;
this.next = next;
}
public final K getKey() {
return key;
}
public final V getValue() {
return value;
}
public final V setValue(V value) {
V oldValue = this.value;
this.value = value;
return oldValue;
}
@Override public final boolean equals(Object o) {
if (!(o instanceof Entry)) {
return false;
}
Entry<?, ?> e = (Entry<?, ?>) o;
return Objects.equal(e.getKey(), key)
&& Objects.equal(e.getValue(), value);
}
@Override public final int hashCode() {
return (key == null ? 0 : key.hashCode()) ^
(value == null ? 0 : value.hashCode());
}
@Override public final String toString() {
return key + "=" + value;
}
}
private abstract class HashIterator {
int nextIndex;
HashMapEntry<K, V> nextEntry = entryForNullKey;
HashMapEntry<K, V> lastEntryReturned;
int expectedModCount = modCount;
HashIterator() {
if (nextEntry == null) {
HashMapEntry<K, V>[] tab = table;
HashMapEntry<K, V> next = null;
while (next == null && nextIndex < tab.length) {
next = tab[nextIndex++];
}
nextEntry = next;
}
}
public boolean hasNext() {
return nextEntry != null;
}
HashMapEntry<K, V> nextEntry() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
if (nextEntry == null)
throw new NoSuchElementException();
HashMapEntry<K, V> entryToReturn = nextEntry;
HashMapEntry<K, V>[] tab = table;
HashMapEntry<K, V> next = entryToReturn.next;
while (next == null && nextIndex < tab.length) {
next = tab[nextIndex++];
}
nextEntry = next;
return lastEntryReturned = entryToReturn;
}
public void remove() {
if (lastEntryReturned == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
HashMap.this.remove(lastEntryReturned.key);
lastEntryReturned = null;
expectedModCount = modCount;
}
}
private final class KeyIterator extends HashIterator
implements Iterator<K> {
public K next() { return nextEntry().key; }
}
private final class ValueIterator extends HashIterator
implements Iterator<V> {
public V next() { return nextEntry().value; }
}
private final class EntryIterator extends HashIterator
implements Iterator<Entry<K, V>> {
public Entry<K, V> next() { return nextEntry(); }
}
/**
* Returns true if this map contains the specified mapping.
*/
private boolean containsMapping(Object key, Object value) {
if (key == null) {
HashMapEntry<K, V> e = entryForNullKey;
return e != null && Objects.equal(value, e.value);
}
int hash = secondaryHash(key.hashCode());
HashMapEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
for (HashMapEntry<K, V> e = tab[index]; e != null; e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
return Objects.equal(value, e.value);
}
}
return false; // No entry for key
}
/**
* Removes the mapping from key to value and returns true if this mapping
* exists; otherwise, returns does nothing and returns false.
*/
private boolean removeMapping(Object key, Object value) {
if (key == null) {
HashMapEntry<K, V> e = entryForNullKey;
if (e == null || !Objects.equal(value, e.value)) {
return false;
}
entryForNullKey = null;
modCount++;
size--;
postRemove(e);
return true;
}
int hash = secondaryHash(key.hashCode());
HashMapEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
for (HashMapEntry<K, V> e = tab[index], prev = null;
e != null; prev = e, e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
if (!Objects.equal(value, e.value)) {
return false; // Map has wrong value for key
}
if (prev == null) {
tab[index] = e.next;
} else {
prev.next = e.next;
}
modCount++;
size--;
postRemove(e);
return true;
}
}
return false; // No entry for key
}
// Subclass (LinkedHashMap) overrides these for correct iteration order
Iterator<K> newKeyIterator() { return new KeyIterator(); }
Iterator<V> newValueIterator() { return new ValueIterator(); }
Iterator<Entry<K, V>> newEntryIterator() { return new EntryIterator(); }
private final class KeySet extends AbstractSet<K> {
public Iterator<K> iterator() {
return newKeyIterator();
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
int oldSize = size;
HashMap.this.remove(o);
return size != oldSize;
}
public void clear() {
HashMap.this.clear();
}
}
private final class Values extends AbstractCollection<V> {
public Iterator<V> iterator() {
return newValueIterator();
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
HashMap.this.clear();
}
}
private final class EntrySet extends AbstractSet<Entry<K, V>> {
public Iterator<Entry<K, V>> iterator() {
return newEntryIterator();
}
public boolean contains(Object o) {
if (!(o instanceof Entry))
return false;
Entry<?, ?> e = (Entry<?, ?>) o;
return containsMapping(e.getKey(), e.getValue());
}
public boolean remove(Object o) {
if (!(o instanceof Entry))
return false;
Entry<?, ?> e = (Entry<?, ?>)o;
return removeMapping(e.getKey(), e.getValue());
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public void clear() {
HashMap.this.clear();
}
}
/**
* 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 or upper bits.
*/
private static int secondaryHash(int h) {
// Doug Lea's supplemental hash function
h ^= (h >>> 20) ^ (h >>> 12);
return h ^ (h >>> 7) ^ (h >>> 4);
}
/**
* Returns the smallest power of two >= its argument, with several caveats:
* If the argument is negative but not Integer.MIN_VALUE, the method returns
* zero. If the argument is > 2^30 or equal to Integer.MIN_VALUE, the method
* returns Integer.MIN_VALUE. If the argument is zero, the method returns
* zero.
*/
private static int roundUpToPowerOfTwo(int i) {
i--; // If input is a power of two, shift its high-order bit right
// "Smear" the high-order bit all the way to the right
i |= i >>> 1;
i |= i >>> 2;
i |= i >>> 4;
i |= i >>> 8;
i |= i >>> 16;
return i + 1;
}
private static final long serialVersionUID = 362498820763181265L;
private static final ObjectStreamField[] serialPersistentFields = {
new ObjectStreamField("loadFactor", float.class)
};
private void writeObject(ObjectOutputStream stream) throws IOException {
// Emulate loadFactor field for other implementations to read
ObjectOutputStream.PutField fields = stream.putFields();
fields.put("loadFactor", DEFAULT_LOAD_FACTOR);
stream.writeFields();
stream.writeInt(table.length); // Capacity
stream.writeInt(size);
for (Entry<K, V> e : entrySet()) {
stream.writeObject(e.getKey());
stream.writeObject(e.getValue());
}
}
private void readObject(ObjectInputStream stream) throws IOException,
ClassNotFoundException {
stream.defaultReadObject();
int capacity = stream.readInt();
if (capacity < 0) {
throw new InvalidObjectException("Capacity: " + capacity);
}
if (capacity < MINIMUM_CAPACITY) {
capacity = MINIMUM_CAPACITY;
} else if (capacity > MAXIMUM_CAPACITY) {
capacity = MAXIMUM_CAPACITY;
} else {
capacity = roundUpToPowerOfTwo(capacity);
}
makeTable(capacity);
int size = stream.readInt();
if (size < 0) {
throw new InvalidObjectException("Size: " + size);
}
init(); // Give subclass (LinkedHashMap) a chance to initialize itself
for (int i = 0; i < size; i++) {
@SuppressWarnings("unchecked") K key = (K) stream.readObject();
@SuppressWarnings("unchecked") V val = (V) stream.readObject();
constructorPut(key, val);
}
}
}