HashMap是一個散列表，儲存的內容是鍵值對（key-value）映射。 HashMap繼承於AbstractMap並實作了Map、Cloneable、Serializable介面。
（1）HashMap不是執行緒安全的，同時key-value都可以是null，而且是無序的。
（2）HashMap的初始大小為16，最大大小為2的30次方，預設的載入因子是0.75。
（3）初始容量只是哈希表在創建時的容量，加載因子是哈希表在其容量自動增加之前可以達到多滿的一種尺度。當雜湊表中的條目數超出了載入因子與目前容量的乘積時，就需要對該雜湊表進行rehash操作（重建內部的資料結構）
HashMap與Map關係如下:
（1）HashMap繼承於AbstractMap類，實作了Map介面。
（2）HashMap透過拉鍊法實作哈希表。幾個重要的成員變數有：table，size，threshold，loadFactor，modCount。
table是一個Entry[]陣列類型，Entry其實是一個單向鍊錶，HashMap的key-value都儲存在這個陣列中。
size是HashMap的大小，它是HashMap保存的鍵值對的數量。
threshold是HashMap的閾值，用於判斷是否需要調整HashMap的容量，threshold的值等於容量乘以加載因子，當HashMap中儲存的資料達到threshold時，就需要將HashMap的容量加倍。
loadFactor載入因子
modCount用來實作fail-fast機制。
HashMap的遍歷方式：
（1）遍歷HashMap的鍵值對：第一步是取得透過entrySet()函數來獲得entry集合，第二步透過Iterator迭代器遍歷entry集合獲得資料
Integer Iterator =map.entrySet().iterator()(iterator.hasNext())
{
Map.Entry entry=(Map.Entry)iterator.next()key=(String)enrty.getKey()value=(Integer)entry.getValue()}
（2）遍歷HashMap的鍵，透過key來獲得value
=Integer =Inerator =map.keySet().iterator()(iterator.hasNext())
{
key=(String)iterator.next()value=(Integer)map.get(key)}
（3 ）遍歷HashMap的值：第一步根據value獲得值集合，對值集合進行迭代遍歷
=Collection =map.values()Iterator = .iterator()(iterator.hasNext())
{
value=(Integer)iterator.next()}
常用的函數：
() Object () (Object key) (Object value) Set<entry>> () (Object key) () Set () (keyvalue) (Map ? > map) (Object key) () Collection ()</entry>
HashMap範例程式碼：
public class Hello {
public void testHashMapAPIs()
{
Random r = new Random();
HashMap<string> map = new HashMap();
map.put("one", r.nextInt(10));
map.put("two", r.nextInt(10));
map.put("three", r.nextInt(10));
System.out.println("map:"+map );
Iterator iter = map.entrySet().iterator();
while(iter.hasNext())
{
Map.Entry entry = (Map.Entry)iter.next();
System.out.println("key : "+ entry.getKey() +",value:"+entry.getValue());
}
System.out.println("size:"+map.size());
System.out.println("contains key two : "+map.containsKey("two"));
System.out.println("contains key five : "+map.containsKey("five"));
System.out.println("contains value 0 : "+map.containsValue(new Integer(0)));
map.remove("three");
System.out.println("map:"+map );
map.clear();
System.out.println((map.isEmpty()?"map is empty":"map is not empty") );
}
public static void main(String[] args) {
Hello hello=new Hello();
hello.testHashMapAPIs();
}
}</string>
執行結果：
map:{one=3, two=9, three=9}
key : one,value:3
key : two,value:9
key : three,value:9
size:3
contains key two : true
contains key five : false
contains value 0 : false
map:{one=3, two=9}
map is empty#java8中HashMap原始碼分析：
public class HashMap<k> extends AbstractMap<k>
implements Map<k>, Cloneable, Serializable {
private static final long serialVersionUID = 362498820763181265L;
static final int DEFAULT_INITIAL_CAPACITY = 1 implements Map.Entry<k> {
final int hash;
final K key;
V value;
Node<k> next;
Node(int hash, K key, V value, Node<k> next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
public final K getKey() {
return key;
}
public final V getValue() {
return value;
}
public final String toString() {
return key + "=" + value;
}
public final int hashCode() {
return Objects.hashCode(key) ^ Objects.hashCode(value);
}
public final V setValue(V newValue) {
V oldValue = value;
value = newValue;
return oldValue;
}
public final boolean equals(Object o) {
if (o == this)
return true;
if (o instanceof Map.Entry) {
Map.Entry, ?> e = (Map.Entry, ?>) o;
if (Objects.equals(key, e.getKey()) &&
Objects.equals(value, e.getValue()))
return true;
}
return false;
}
}
//计算Hash
static final int hash(Object key) {
int h;
return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}
//返回类
static Class> comparableClassFor(Object x) {
if (x instanceof Comparable) {
Class> c; Type[] ts, as; Type t; ParameterizedType p;
if ((c = x.getClass()) == String.class) // bypass checks
return c;
if ((ts = c.getGenericInterfaces()) != null) {
for (int i = 0; i kc, Object k, Object x) {
return (x == null || x.getClass() != kc ? 0 :
((Comparable)k).compareTo(x));
}
static final int tableSizeFor(int cap) {
int n = cap - 1;
n |= n >>> 1;
n |= n >>> 2;
n |= n >>> 4;
n |= n >>> 8;
n |= n >>> 16;
return (n = MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
}
transient Node<k>[] table;//数据表
transient Set<map.entry>> entrySet;//实体集合
transient int size;//大小
transient int modCount;//用来实现fail-fast
int threshold;//值为capacity * load factor
final float loadFactor;//hashtable的加载因子
//构造函数，初始化容量大小和加载因子
public HashMap(int initialCapacity, float loadFactor) {
if (initialCapacity MAXIMUM_CAPACITY)
initialCapacity = MAXIMUM_CAPACITY;
if (loadFactor m) {
this.loadFactor = DEFAULT_LOAD_FACTOR;
putMapEntries(m, false);
}
final void putMapEntries(Map extends K, ? extends V> m, boolean evict) {
int s = m.size();
if (s > 0) {
if (table == null) { // pre-size
float ft = ((float)s / loadFactor) + 1.0F;
int t = ((ft threshold)
threshold = tableSizeFor(t);
}
else if (s > threshold)
resize();
for (Map.Entry extends K, ? extends V> e : m.entrySet()) {
K key = e.getKey();
V value = e.getValue();
putVal(hash(key), key, value, false, evict);
}
}
}
//返回大小
public int size() {
return size;
}
//判断是否为空
public boolean isEmpty() {
return size == 0;
}
//通过key获得值
public V get(Object key) {
Node<k> e;
return (e = getNode(hash(key), key)) == null ? null : e.value;
}
//通过hash和key获得节点
final Node<k> getNode(int hash, Object key) {
Node<k>[] tab; Node<k> first, e; int n; K k;
if ((tab = table) != null && (n = tab.length) > 0 &&
(first = tab[(n - 1) & hash]) != null) {
if (first.hash == hash && // always check first node
((k = first.key) == key || (key != null && key.equals(k))))
return first;
if ((e = first.next) != null) {
if (first instanceof TreeNode)
return ((TreeNode<k>)first).getTreeNode(hash, key);
do {
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
return e;
} while ((e = e.next) != null);
}
}
return null;
}
//是否含有某个key
public boolean containsKey(Object key) {
return getNode(hash(key), key) != null;
}
//如果之前存在key的value值，则替换掉
public V put(K key, V value) {
return putVal(hash(key), key, value, false, true);
}
final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
boolean evict) {
Node<k>[] tab; Node<k> p; int n, i;
if ((tab = table) == null || (n = tab.length) == 0)
n = (tab = resize()).length;
if ((p = tab[i = (n - 1) & hash]) == null)
tab[i] = newNode(hash, key, value, null);
else {
Node<k> e; K k;
if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))
e = p;
else if (p instanceof TreeNode)
e = ((TreeNode<k>)p).putTreeVal(this, tab, hash, key, value);
else {
for (int binCount = 0; ; ++binCount) {
if ((e = p.next) == null) {
p.next = newNode(hash, key, value, null);
if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
treeifyBin(tab, hash);
break;
}
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
break;
p = e;
}
}
if (e != null) { // existing mapping for key
V oldValue = e.value;
if (!onlyIfAbsent || oldValue == null)
e.value = value;
afterNodeAccess(e);
return oldValue;
}
}
++modCount;
if (++size > threshold)
resize();
afterNodeInsertion(evict);
return null;
}
//改变大小
final Node<k>[] resize() {
Node<k>[] oldTab = table;
int oldCap = (oldTab == null) ? 0 : oldTab.length;
int oldThr = threshold;
int newCap, newThr = 0;
if (oldCap > 0) {
if (oldCap >= MAXIMUM_CAPACITY) {
threshold = Integer.MAX_VALUE;
return oldTab;
}
else if ((newCap = oldCap = DEFAULT_INITIAL_CAPACITY)
newThr = oldThr 0) // initial capacity was placed in threshold
newCap = oldThr;
else { // zero initial threshold signifies using defaults
newCap = DEFAULT_INITIAL_CAPACITY;
newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
}
if (newThr == 0) {
float ft = (float)newCap * loadFactor;
newThr = (newCap [] newTab = (Node<k>[])new Node[newCap];
table = newTab;
if (oldTab != null) {
for (int j = 0; j e;
if ((e = oldTab[j]) != null) {
oldTab[j] = null;
if (e.next == null)
newTab[e.hash & (newCap - 1)] = e;
else if (e instanceof TreeNode)
((TreeNode<k>)e).split(this, newTab, j, oldCap);
else { // preserve order
Node<k> loHead = null, loTail = null;
Node<k> hiHead = null, hiTail = null;
Node<k> next;
do {
next = e.next;
if ((e.hash & oldCap) == 0) {
if (loTail == null)
loHead = e;
else
loTail.next = e;
loTail = e;
}
else {
if (hiTail == null)
hiHead = e;
else
hiTail.next = e;
hiTail = e;
}
} while ((e = next) != null);
if (loTail != null) {
loTail.next = null;
newTab[j] = loHead;
}
if (hiTail != null) {
hiTail.next = null;
newTab[j + oldCap] = hiHead;
}
}
}
}
}
return newTab;
}
final void treeifyBin(Node<k>[] tab, int hash) {
int n, index; Node<k> e;
if (tab == null || (n = tab.length) hd = null, tl = null;
do {
TreeNode<k> p = replacementTreeNode(e, null);
if (tl == null)
hd = p;
else {
p.prev = tl;
tl.next = p;
}
tl = p;
} while ((e = e.next) != null);
if ((tab[index] = hd) != null)
hd.treeify(tab);
}
}
public void putAll(Map extends K, ? extends V> m) {
putMapEntries(m, true);
}
public V remove(Object key) {
Node<k> e;
return (e = removeNode(hash(key), key, null, false, true)) == null ?
null : e.value;
}
final Node<k> removeNode(int hash, Object key, Object value,
boolean matchValue, boolean movable) {
Node<k>[] tab; Node<k> p; int n, index;
if ((tab = table) != null && (n = tab.length) > 0 &&
(p = tab[index = (n - 1) & hash]) != null) {
Node<k> node = null, e; K k; V v;
if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))
node = p;
else if ((e = p.next) != null) {
if (p instanceof TreeNode)
node = ((TreeNode<k>)p).getTreeNode(hash, key);
else {
do {
if (e.hash == hash &&
((k = e.key) == key ||
(key != null && key.equals(k)))) {
node = e;
break;
}
p = e;
} while ((e = e.next) != null);
}
}
if (node != null && (!matchValue || (v = node.value) == value ||
(value != null && value.equals(v)))) {
if (node instanceof TreeNode)
((TreeNode<k>)node).removeTreeNode(this, tab, movable);
else if (node == p)
tab[index] = node.next;
else
p.next = node.next;
++modCount;
--size;
afterNodeRemoval(node);
return node;
}
}
return null;
}
public void clear() {
Node<k>[] tab;
modCount++;
if ((tab = table) != null && size > 0) {
size = 0;
for (int i = 0; i [] tab; V v;
if ((tab = table) != null && size > 0) {
for (int i = 0; i e = tab[i]; e != null; e = e.next) {
if ((v = e.value) == value ||
(value != null && value.equals(v)))
return true;
}
}
}
return false;
}
public Set<k> keySet() {
Set<k> ks;
return (ks = keySet) == null ? (keySet = new KeySet()) : ks;
}
final class KeySet extends AbstractSet<k> {
public final int size() { return size; }
public final void clear() { HashMap.this.clear(); }
public final Iterator<k> iterator() { return new KeyIterator(); }
public final boolean contains(Object o) { return containsKey(o); }
public final boolean remove(Object key) {
return removeNode(hash(key), key, null, false, true) != null;
}
public final Spliterator<k> spliterator() {
return new KeySpliterator(HashMap.this, 0, -1, 0, 0);
}
public final void forEach(Consumer super K> action) {
Node<k>[] tab;
if (action == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i e = tab[i]; e != null; e = e.next)
action.accept(e.key);
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
}
public Collection<v> values() {
Collection<v> vs;
return (vs = values) == null ? (values = new Values()) : vs;
}
final class Values extends AbstractCollection<v> {
public final int size() { return size; }
public final void clear() { HashMap.this.clear(); }
public final Iterator<v> iterator() { return new ValueIterator(); }
public final boolean contains(Object o) { return containsValue(o); }
public final Spliterator<v> spliterator() {
return new ValueSpliterator(HashMap.this, 0, -1, 0, 0);
}
public final void forEach(Consumer super V> action) {
Node<k>[] tab;
if (action == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i e = tab[i]; e != null; e = e.next)
action.accept(e.value);
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
}
public Set<map.entry>> entrySet() {
Set<map.entry>> es;
return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
}
final class EntrySet extends AbstractSet<map.entry>> {
public final int size() { return size; }
public final void clear() { HashMap.this.clear(); }
public final Iterator<map.entry>> iterator() {
return new EntryIterator();
}
public final boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry,?> e = (Map.Entry,?>) o;
Object key = e.getKey();
Node<k> candidate = getNode(hash(key), key);
return candidate != null && candidate.equals(e);
}
public final boolean remove(Object o) {
if (o instanceof Map.Entry) {
Map.Entry,?> e = (Map.Entry,?>) o;
Object key = e.getKey();
Object value = e.getValue();
return removeNode(hash(key), key, value, true, true) != null;
}
return false;
}
public final Spliterator<map.entry>> spliterator() {
return new EntrySpliterator(HashMap.this, 0, -1, 0, 0);
}
public final void forEach(Consumer super Map.Entry<k>> action) {
Node<k>[] tab;
if (action == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i e = tab[i]; e != null; e = e.next)
action.accept(e);
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
}
// Overrides of JDK8 Map extension methods
@Override
public V getOrDefault(Object key, V defaultValue) {
Node<k> e;
return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
}
@Override
public V putIfAbsent(K key, V value) {
return putVal(hash(key), key, value, true, true);
}
@Override
public boolean remove(Object key, Object value) {
return removeNode(hash(key), key, value, true, true) != null;
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
Node<k> e; V v;
if ((e = getNode(hash(key), key)) != null &&
((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
e.value = newValue;
afterNodeAccess(e);
return true;
}
return false;
}
@Override
public V replace(K key, V value) {
Node<k> e;
if ((e = getNode(hash(key), key)) != null) {
V oldValue = e.value;
e.value = value;
afterNodeAccess(e);
return oldValue;
}
return null;
}
@Override
public V computeIfAbsent(K key,
Function super K, ? extends V> mappingFunction) {
if (mappingFunction == null)
throw new NullPointerException();
int hash = hash(key);
Node<k>[] tab; Node<k> first; int n, i;
int binCount = 0;
TreeNode<k> t = null;
Node<k> old = null;
if (size > threshold || (tab = table) == null ||
(n = tab.length) == 0)
n = (tab = resize()).length;
if ((first = tab[i = (n - 1) & hash]) != null) {
if (first instanceof TreeNode)
old = (t = (TreeNode<k>)first).getTreeNode(hash, key);
else {
Node<k> e = first; K k;
do {
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
old = e;
break;
}
++binCount;
} while ((e = e.next) != null);
}
V oldValue;
if (old != null && (oldValue = old.value) != null) {
afterNodeAccess(old);
return oldValue;
}
}
V v = mappingFunction.apply(key);
if (v == null) {
return null;
} else if (old != null) {
old.value = v;
afterNodeAccess(old);
return v;
}
else if (t != null)
t.putTreeVal(this, tab, hash, key, v);
else {
tab[i] = newNode(hash, key, v, first);
if (binCount >= TREEIFY_THRESHOLD - 1)
treeifyBin(tab, hash);
}
++modCount;
++size;
afterNodeInsertion(true);
return v;
}
public V computeIfPresent(K key,
BiFunction super K, ? super V, ? extends V> remappingFunction) {
if (remappingFunction == null)
throw new NullPointerException();
Node<k> e; V oldValue;
int hash = hash(key);
if ((e = getNode(hash, key)) != null &&
(oldValue = e.value) != null) {
V v = remappingFunction.apply(key, oldValue);
if (v != null) {
e.value = v;
afterNodeAccess(e);
return v;
}
else
removeNode(hash, key, null, false, true);
}
return null;
}
@Override
public V compute(K key,
BiFunction super K, ? super V, ? extends V> remappingFunction) {
if (remappingFunction == null)
throw new NullPointerException();
int hash = hash(key);
Node<k>[] tab; Node<k> first; int n, i;
int binCount = 0;
TreeNode<k> t = null;
Node<k> old = null;
if (size > threshold || (tab = table) == null ||
(n = tab.length) == 0)
n = (tab = resize()).length;
if ((first = tab[i = (n - 1) & hash]) != null) {
if (first instanceof TreeNode)
old = (t = (TreeNode<k>)first).getTreeNode(hash, key);
else {
Node<k> e = first; K k;
do {
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
old = e;
break;
}
++binCount;
} while ((e = e.next) != null);
}
}
V oldValue = (old == null) ? null : old.value;
V v = remappingFunction.apply(key, oldValue);
if (old != null) {
if (v != null) {
old.value = v;
afterNodeAccess(old);
}
else
removeNode(hash, key, null, false, true);
}
else if (v != null) {
if (t != null)
t.putTreeVal(this, tab, hash, key, v);
else {
tab[i] = newNode(hash, key, v, first);
if (binCount >= TREEIFY_THRESHOLD - 1)
treeifyBin(tab, hash);
}
++modCount;
++size;
afterNodeInsertion(true);
}
return v;
}
@Override
public V merge(K key, V value,
BiFunction super V, ? super V, ? extends V> remappingFunction) {
if (value == null)
throw new NullPointerException();
if (remappingFunction == null)
throw new NullPointerException();
int hash = hash(key);
Node<k>[] tab; Node<k> first; int n, i;
int binCount = 0;
TreeNode<k> t = null;
Node<k> old = null;
if (size > threshold || (tab = table) == null ||
(n = tab.length) == 0)
n = (tab = resize()).length;
if ((first = tab[i = (n - 1) & hash]) != null) {
if (first instanceof TreeNode)
old = (t = (TreeNode<k>)first).getTreeNode(hash, key);
else {
Node<k> e = first; K k;
do {
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k)))) {
old = e;
break;
}
++binCount;
} while ((e = e.next) != null);
}
}
if (old != null) {
V v;
if (old.value != null)
v = remappingFunction.apply(old.value, value);
else
v = value;
if (v != null) {
old.value = v;
afterNodeAccess(old);
}
else
removeNode(hash, key, null, false, true);
return v;
}
if (value != null) {
if (t != null)
t.putTreeVal(this, tab, hash, key, value);
else {
tab[i] = newNode(hash, key, value, first);
if (binCount >= TREEIFY_THRESHOLD - 1)
treeifyBin(tab, hash);
}
++modCount;
++size;
afterNodeInsertion(true);
}
return value;
}
@Override
public void forEach(BiConsumer super K, ? super V> action) {
Node<k>[] tab;
if (action == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i e = tab[i]; e != null; e = e.next)
action.accept(e.key, e.value);
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
@Override
public void replaceAll(BiFunction super K, ? super V, ? extends V> function) {
Node<k>[] tab;
if (function == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i e = tab[i]; e != null; e = e.next) {
e.value = function.apply(e.key, e.value);
}
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
@SuppressWarnings("unchecked")
@Override
public Object clone() {
HashMap<k> result;
try {
result = (HashMap<k>)super.clone();
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError(e);
}
result.reinitialize();
result.putMapEntries(this, false);
return result;
}
final float loadFactor() { return loadFactor; }
final int capacity() {
return (table != null) ? table.length :
(threshold > 0) ? threshold :
DEFAULT_INITIAL_CAPACITY;
}
private void writeObject(java.io.ObjectOutputStream s)
throws IOException {
int buckets = capacity();
// Write out the threshold, loadfactor, and any hidden stuff
s.defaultWriteObject();
s.writeInt(buckets);
s.writeInt(size);
internalWriteEntries(s);
}
private void readObject(java.io.ObjectInputStream s)
throws IOException, ClassNotFoundException {
// Read in the threshold (ignored), loadfactor, and any hidden stuff
s.defaultReadObject();
reinitialize();
if (loadFactor 0) { // (if zero, use defaults)
// Size the table using given load factor only if within
// range of 0.25...4.0
float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
float fc = (float)mappings / lf + 1.0f;
int cap = ((fc = MAXIMUM_CAPACITY) ?
MAXIMUM_CAPACITY :
tableSizeFor((int)fc));
float ft = (float)cap * lf;
threshold = ((cap [] tab = (Node<k>[])new Node[cap];
table = tab;
// Read the keys and values, and put the mappings in the HashMap
for (int i = 0; i next; // next entry to return
Node<k> current; // current entry
int expectedModCount; // for fast-fail
int index; // current slot
HashIterator() {
expectedModCount = modCount;
Node<k>[] t = table;
current = next = null;
index = 0;
if (t != null && size > 0) { // advance to first entry
do {} while (index nextNode() {
Node<k>[] t;
Node<k> e = next;
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
if (e == null)
throw new NoSuchElementException();
if ((next = (current = e).next) == null && (t = table) != null) {
do {} while (index p = current;
if (p == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
current = null;
K key = p.key;
removeNode(hash(key), key, null, false, false);
expectedModCount = modCount;
}
}
final class KeyIterator extends HashIterator
implements Iterator<k> {
public final K next() { return nextNode().key; }
}
final class ValueIterator extends HashIterator
implements Iterator<v> {
public final V next() { return nextNode().value; }
}
final class EntryIterator extends HashIterator
implements Iterator<map.entry>> {
public final Map.Entry<k> next() { return nextNode(); }
}
static class HashMapSpliterator<k> {
final HashMap<k> map;
Node<k> current; // current node
int index; // current index, modified on advance/split
int fence; // one past last index
int est; // size estimate
int expectedModCount; // for comodification checks
HashMapSpliterator(HashMap<k> 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) m = map;
est = m.size;
expectedModCount = m.modCount;
Node<k>[] tab = m.table;
hi = fence = (tab == null) ? 0 : tab.length;
}
return hi;
}
public final long estimateSize() {
getFence(); // force init
return (long) est;
}
}
static final class KeySpliterator<k>
extends HashMapSpliterator<k>
implements Spliterator<k> {
KeySpliterator(HashMap<k> m, int origin, int fence, int est,
int expectedModCount) {
super(m, origin, fence, est, expectedModCount);
}
public KeySpliterator<k> trySplit() {
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
return (lo >= mid || current != null) ? null :
new KeySpliterator(map, lo, index = mid, est >>>= 1,
expectedModCount);
}
public void forEachRemaining(Consumer super K> action) {
int i, hi, mc;
if (action == null)
throw new NullPointerException();
HashMap<k> m = map;
Node<k>[] tab = m.table;
if ((hi = fence) = hi &&
(i = index) >= 0 && (i p = current;
current = null;
do {
if (p == null)
p = tab[i++];
else {
action.accept(p.key);
p = p.next;
}
} while (p != null || i action) {
int hi;
if (action == null)
throw new NullPointerException();
Node<k>[] tab = map.table;
if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
while (current != null || index
extends HashMapSpliterator<k>
implements Spliterator<v> {
ValueSpliterator(HashMap<k> m, int origin, int fence, int est,
int expectedModCount) {
super(m, origin, fence, est, expectedModCount);
}
public ValueSpliterator<k> trySplit() {
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
return (lo >= mid || current != null) ? null :
new ValueSpliterator(map, lo, index = mid, est >>>= 1,
expectedModCount);
}
public void forEachRemaining(Consumer super V> action) {
int i, hi, mc;
if (action == null)
throw new NullPointerException();
HashMap<k> m = map;
Node<k>[] tab = m.table;
if ((hi = fence) = hi &&
(i = index) >= 0 && (i p = current;
current = null;
do {
if (p == null)
p = tab[i++];
else {
action.accept(p.value);
p = p.next;
}
} while (p != null || i action) {
int hi;
if (action == null)
throw new NullPointerException();
Node<k>[] tab = map.table;
if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
while (current != null || index
extends HashMapSpliterator<k>
implements Spliterator<map.entry>> {
EntrySpliterator(HashMap<k> m, int origin, int fence, int est,
int expectedModCount) {
super(m, origin, fence, est, expectedModCount);
}
public EntrySpliterator<k> trySplit() {
int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
return (lo >= mid || current != null) ? null :
new EntrySpliterator(map, lo, index = mid, est >>>= 1,
expectedModCount);
}
public void forEachRemaining(Consumer super Map.Entry<k>> action) {
int i, hi, mc;
if (action == null)
throw new NullPointerException();
HashMap<k> m = map;
Node<k>[] tab = m.table;
if ((hi = fence) = hi &&
(i = index) >= 0 && (i p = current;
current = null;
do {
if (p == null)
p = tab[i++];
else {
action.accept(p);
p = p.next;
}
} while (p != null || i > action) {
int hi;
if (action == null)
throw new NullPointerException();
Node<k>[] tab = map.table;
if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
while (current != null || index e = current;
current = current.next;
action.accept(e);
if (map.modCount != expectedModCount)
throw new ConcurrentModificationException();
return true;
}
}
}
return false;
}
public int characteristics() {
return (fence newNode(int hash, K key, V value, Node<k> next) {
return new Node(hash, key, value, next);
}
// For conversion from TreeNodes to plain nodes
Node<k> replacementNode(Node<k> p, Node<k> next) {
return new Node(p.hash, p.key, p.value, next);
}
// Create a tree bin node
TreeNode<k> newTreeNode(int hash, K key, V value, Node<k> next) {
return new TreeNode(hash, key, value, next);
}
// For treeifyBin
TreeNode<k> replacementTreeNode(Node<k> p, Node<k> next) {
return new TreeNode(p.hash, p.key, p.value, next);
}
void reinitialize() {
table = null;
entrySet = null;
keySet = null;
values = null;
modCount = 0;
threshold = 0;
size = 0;
}
// Callbacks to allow LinkedHashMap post-actions
void afterNodeAccess(Node<k> p) { }
void afterNodeInsertion(boolean evict) { }
void afterNodeRemoval(Node<k> p) { }
// Called only from writeObject, to ensure compatible ordering.
void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
Node<k>[] tab;
if (size > 0 && (tab = table) != null) {
for (int i = 0; i e = tab[i]; e != null; e = e.next) {
s.writeObject(e.key);
s.writeObject(e.value);
}
}
}
}
static final class TreeNode<k> extends LinkedHashMap.Entry<k> {
TreeNode<k> parent; // red-black tree links
TreeNode<k> left;
TreeNode<k> right;
TreeNode<k> prev; // needed to unlink next upon deletion
boolean red;
TreeNode(int hash, K key, V val, Node<k> next) {
super(hash, key, val, next);
}
/**
* Returns root of tree containing this node.
*/
final TreeNode<k> root() {
for (TreeNode<k> r = this, p;;) {
if ((p = r.parent) == null)
return r;
r = p;
}
}
/**
* Ensures that the given root is the first node of its bin.
*/
static <k> void moveRootToFront(Node<k>[] tab, TreeNode<k> root) {
int n;
if (root != null && tab != null && (n = tab.length) > 0) {
int index = (n - 1) & root.hash;
TreeNode<k> first = (TreeNode<k>)tab[index];
if (root != first) {
Node<k> rn;
tab[index] = root;
TreeNode<k> rp = root.prev;
if ((rn = root.next) != null)
((TreeNode<k>)rn).prev = rp;
if (rp != null)
rp.next = rn;
if (first != null)
first.prev = root;
root.next = first;
root.prev = null;
}
assert checkInvariants(root);
}
}
final TreeNode<k> find(int h, Object k, Class> kc) {
TreeNode<k> p = this;
do {
int ph, dir; K pk;
TreeNode<k> pl = p.left, pr = p.right, q;
if ((ph = p.hash) > h)
p = pl;
else if (ph getTreeNode(int h, Object k) {
return ((parent != null) ? root() : this).find(h, k, null);
}
static int tieBreakOrder(Object a, Object b) {
int d;
if (a == null || b == null ||
(d = a.getClass().getName().
compareTo(b.getClass().getName())) == 0)
d = (System.identityHashCode(a) [] tab) {
TreeNode<k> root = null;
for (TreeNode<k> x = this, next; x != null; x = next) {
next = (TreeNode<k>)x.next;
x.left = x.right = null;
if (root == null) {
x.parent = null;
x.red = false;
root = x;
}
else {
K k = x.key;
int h = x.hash;
Class> kc = null;
for (TreeNode<k> p = root;;) {
int dir, ph;
K pk = p.key;
if ((ph = p.hash) > h)
dir = -1;
else if (ph xp = p;
if ((p = (dir untreeify(HashMap<k> map) {
Node<k> hd = null, tl = null;
for (Node<k> q = this; q != null; q = q.next) {
Node<k> p = map.replacementNode(q, null);
if (tl == null)
hd = p;
else
tl.next = p;
tl = p;
}
return hd;
}
final TreeNode<k> putTreeVal(HashMap<k> map, Node<k>[] tab,
int h, K k, V v) {
Class> kc = null;
boolean searched = false;
TreeNode<k> root = (parent != null) ? root() : this;
for (TreeNode<k> p = root;;) {
int dir, ph; K pk;
if ((ph = p.hash) > h)
dir = -1;
else if (ph q, ch;
searched = true;
if (((ch = p.left) != null &&
(q = ch.find(h, k, kc)) != null) ||
((ch = p.right) != null &&
(q = ch.find(h, k, kc)) != null))
return q;
}
dir = tieBreakOrder(k, pk);
}
TreeNode<k> xp = p;
if ((p = (dir xpn = xp.next;
TreeNode<k> x = map.newTreeNode(h, k, v, xpn);
if (dir )xpn).prev = x;
moveRootToFront(tab, balanceInsertion(root, x));
return null;
}
}
}
final void removeTreeNode(HashMap<k> map, Node<k>[] tab,
boolean movable) {
int n;
if (tab == null || (n = tab.length) == 0)
return;
int index = (n - 1) & hash;
TreeNode<k> first = (TreeNode<k>)tab[index], root = first, rl;
TreeNode<k> succ = (TreeNode<k>)next, pred = prev;
if (pred == null)
tab[index] = first = succ;
else
pred.next = succ;
if (succ != null)
succ.prev = pred;
if (first == null)
return;
if (root.parent != null)
root = root.root();
if (root == null || root.right == null ||
(rl = root.left) == null || rl.left == null) {
tab[index] = first.untreeify(map); // too small
return;
}
TreeNode<k> p = this, pl = left, pr = right, replacement;
if (pl != null && pr != null) {
TreeNode<k> s = pr, sl;
while ((sl = s.left) != null) // find successor
s = sl;
boolean c = s.red; s.red = p.red; p.red = c; // swap colors
TreeNode<k> sr = s.right;
TreeNode<k> pp = p.parent;
if (s == pr) { // p was s's direct parent
p.parent = s;
s.right = p;
}
else {
TreeNode<k> sp = s.parent;
if ((p.parent = sp) != null) {
if (s == sp.left)
sp.left = p;
else
sp.right = p;
}
if ((s.right = pr) != null)
pr.parent = s;
}
p.left = null;
if ((p.right = sr) != null)
sr.parent = p;
if ((s.left = pl) != null)
pl.parent = s;
if ((s.parent = pp) == null)
root = s;
else if (p == pp.left)
pp.left = s;
else
pp.right = s;
if (sr != null)
replacement = sr;
else
replacement = p;
}
else if (pl != null)
replacement = pl;
else if (pr != null)
replacement = pr;
else
replacement = p;
if (replacement != p) {
TreeNode<k> pp = replacement.parent = p.parent;
if (pp == null)
root = replacement;
else if (p == pp.left)
pp.left = replacement;
else
pp.right = replacement;
p.left = p.right = p.parent = null;
}
TreeNode<k> r = p.red ? root : balanceDeletion(root, replacement);
if (replacement == p) { // detach
TreeNode<k> pp = p.parent;
p.parent = null;
if (pp != null) {
if (p == pp.left)
pp.left = null;
else if (p == pp.right)
pp.right = null;
}
}
if (movable)
moveRootToFront(tab, r);
}
final void split(HashMap<k> map, Node<k>[] tab, int index, int bit) {
TreeNode<k> b = this;
// Relink into lo and hi lists, preserving order
TreeNode<k> loHead = null, loTail = null;
TreeNode<k> hiHead = null, hiTail = null;
int lc = 0, hc = 0;
for (TreeNode<k> e = b, next; e != null; e = next) {
next = (TreeNode<k>)e.next;
e.next = null;
if ((e.hash & bit) == 0) {
if ((e.prev = loTail) == null)
loHead = e;
else
loTail.next = e;
loTail = e;
++lc;
}
else {
if ((e.prev = hiTail) == null)
hiHead = e;
else
hiTail.next = e;
hiTail = e;
++hc;
}
}
if (loHead != null) {
if (lc TreeNode<k> rotateLeft(TreeNode<k> root,
TreeNode<k> p) {
TreeNode<k> r, pp, rl;
if (p != null && (r = p.right) != null) {
if ((rl = p.right = r.left) != null)
rl.parent = p;
if ((pp = r.parent = p.parent) == null)
(root = r).red = false;
else if (pp.left == p)
pp.left = r;
else
pp.right = r;
r.left = p;
p.parent = r;
}
return root;
}
static <k> TreeNode<k> rotateRight(TreeNode<k> root,
TreeNode<k> p) {
TreeNode<k> l, pp, lr;
if (p != null && (l = p.left) != null) {
if ((lr = p.left = l.right) != null)
lr.parent = p;
if ((pp = l.parent = p.parent) == null)
(root = l).red = false;
else if (pp.right == p)
pp.right = l;
else
pp.left = l;
l.right = p;
p.parent = l;
}
return root;
}
static <k> TreeNode<k> balanceInsertion(TreeNode<k> root,
TreeNode<k> x) {
x.red = true;
for (TreeNode<k> xp, xpp, xppl, xppr;;) {
if ((xp = x.parent) == null) {
x.red = false;
return x;
}
else if (!xp.red || (xpp = xp.parent) == null)
return root;
if (xp == (xppl = xpp.left)) {
if ((xppr = xpp.right) != null && xppr.red) {
xppr.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
else {
if (x == xp.right) {
root = rotateLeft(root, x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
if (xp != null) {
xp.red = false;
if (xpp != null) {
xpp.red = true;
root = rotateRight(root, xpp);
}
}
}
}
else {
if (xppl != null && xppl.red) {
xppl.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
else {
if (x == xp.left) {
root = rotateRight(root, x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
if (xp != null) {
xp.red = false;
if (xpp != null) {
xpp.red = true;
root = rotateLeft(root, xpp);
}
}
}
}
}
}
static <k> TreeNode<k> balanceDeletion(TreeNode<k> root,
TreeNode<k> x) {
for (TreeNode<k> xp, xpl, xpr;;) {
if (x == null || x == root)
return root;
else if ((xp = x.parent) == null) {
x.red = false;
return x;
}
else if (x.red) {
x.red = false;
return root;
}
else if ((xpl = xp.left) == x) {
if ((xpr = xp.right) != null && xpr.red) {
xpr.red = false;
xp.red = true;
root = rotateLeft(root, xp);
xpr = (xp = x.parent) == null ? null : xp.right;
}
if (xpr == null)
x = xp;
else {
TreeNode<k> sl = xpr.left, sr = xpr.right;
if ((sr == null || !sr.red) &&
(sl == null || !sl.red)) {
xpr.red = true;
x = xp;
}
else {
if (sr == null || !sr.red) {
if (sl != null)
sl.red = false;
xpr.red = true;
root = rotateRight(root, xpr);
xpr = (xp = x.parent) == null ?
null : xp.right;
}
if (xpr != null) {
xpr.red = (xp == null) ? false : xp.red;
if ((sr = xpr.right) != null)
sr.red = false;
}
if (xp != null) {
xp.red = false;
root = rotateLeft(root, xp);
}
x = root;
}
}
}
else { // symmetric
if (xpl != null && xpl.red) {
xpl.red = false;
xp.red = true;
root = rotateRight(root, xp);
xpl = (xp = x.parent) == null ? null : xp.left;
}
if (xpl == null)
x = xp;
else {
TreeNode<k> sl = xpl.left, sr = xpl.right;
if ((sl == null || !sl.red) &&
(sr == null || !sr.red)) {
xpl.red = true;
x = xp;
}
else {
if (sl == null || !sl.red) {
if (sr != null)
sr.red = false;
xpl.red = true;
root = rotateLeft(root, xpl);
xpl = (xp = x.parent) == null ?
null : xp.left;
}
if (xpl != null) {
xpl.red = (xp == null) ? false : xp.red;
if ((sl = xpl.left) != null)
sl.red = false;
}
if (xp != null) {
xp.red = false;
root = rotateRight(root, xp);
}
x = root;
}
}
}
}
}
/**
* Recursive invariant check
*/
static <k> boolean checkInvariants(TreeNode<k> t) {
TreeNode<k> tp = t.parent, tl = t.left, tr = t.right,
tb = t.prev, tn = (TreeNode<k>)t.next;
if (tb != null && tb.next != t)
return false;
if (tn != null && tn.prev != t)
return false;
if (tp != null && t != tp.left && t != tp.right)
return false;
if (tl != null && (tl.parent != t || tl.hash > t.hash))
return false;
if (tr != null && (tr.parent != t || tr.hash </k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></map.entry></k></k></k></k></k></k></v></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></map.entry></v></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></map.entry></k></map.entry></map.entry></map.entry></map.entry></k></v></v></v></v></v></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></k></map.entry></k></k></k></k></k></k></k>以上是Java集合之HashMap詳解的詳細內容。更多資訊請關注PHP中文網其他相關文章！
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