HashMap
类结构
- 继承AbstractMap<K,V>
- 实现Map<K,V>
- Map基本方法
- 实现Cloneable
- 浅克隆
- 实现Serializable
- 序列化
成员变量
// 默认初始化容量
static final int DEFAULT_INITIAL_CAPACITY = 1 << 4;
// 数组最大长度
static final int MAXIMUM_CAPACITY = 1 << 30;
// 默认负载因子
static final float DEFAULT_LOAD_FACTOR = 0.75f;
// 转树阈值
static final int TREEIFY_THRESHOLD = 8;
// 解树阈值(考虑解树性能，变为7时无需变化红黑树；留有缓冲，懒处理)
static final int UNTREEIFY_THRESHOLD = 6;
// 最小树容量
static final int MIN_TREEIFY_CAPACITY = 64;
transient Node<K,V>[] table;
transient Set<Map.Entry<K,V>> entrySet;
transient int size;
transient int modCount;
// 容量阈值
int threshold;
// 负载因子
final float loadFactor;
数据结构
static class Node<K,V> implements Map.Entry<K,V> {
// 内存地址不可改变
final int hash;
// 键值对中键不可修改，hash值需要
final K key;
V value;
Node<K,V> next;
Node(int hash, K key, V value, Node<K,V> 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; }
// 键值分别异或得到结点hash值
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) {
// o属于Map.Entry，进行泛型强转
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
// 使用objects.equals进行综合判断
if (Objects.equals(key, e.getKey()) &&
Objects.equals(value, e.getValue()))
return true;
}
return false;
}
}
interface Entry<K,V> {
K getKey();
V getValue();
V setValue(V value);
boolean equals(Object o);
int hashCode();
// 返回一个基于键进行比较的比较器。比较器会根据键的自然顺序进行比较
public static <K extends Comparable<? super K>, V> Comparator<Map.Entry<K,V>> comparingByKey() {
return (Comparator<Map.Entry<K, V>> & Serializable)
(c1, c2) -> c1.getKey().compareTo(c2.getKey());
}
// 返回一个基于值进行比较的比较器。比较器会根据值的自然顺序进行比较
public static <K, V extends Comparable<? super V>> Comparator<Map.Entry<K,V>> comparingByValue() {
return (Comparator<Map.Entry<K, V>> & Serializable)
(c1, c2) -> c1.getValue().compareTo(c2.getValue());
}
// 返回一个基于键进行比较的比较器，使用给定的自定义比较器来比较键
public static <K, V> Comparator<Map.Entry<K, V>> comparingByKey(Comparator<? super K> cmp) {
Objects.requireNonNull(cmp);
return (Comparator<Map.Entry<K, V>> & Serializable)
(c1, c2) -> cmp.compare(c1.getKey(), c2.getKey());
}
// 返回一个基于值进行比较的比较器，使用给定的自定义比较器来比较值
public static <K, V> Comparator<Map.Entry<K, V>> comparingByValue(Comparator<? super V> cmp) {
Objects.requireNonNull(cmp);
return (Comparator<Map.Entry<K, V>> & Serializable)
(c1, c2) -> cmp.compare(c1.getValue(), c2.getValue());
}
}
静态方法
哈希方法
// 通过将哈希码的高位与低位进行混合，可以更好地充分利用哈希码的信息，提高哈希函数的散列效果和键值的均匀分布
static final int hash(Object key) {
int h;
return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}
比较方法
// 通过类型检查和反射获取实现了 Comparable 接口且泛型参数为对应类的类对象
static Class<?> comparableClassFor(Object x) {
if (x instanceof Comparable) {
Class<?> c;
Type[] ts, as;
Type t;
// 泛型接口，可以返回泛型的实际类型、原始类型、拥有者类型
ParameterizedType p;
// 放行string类型
if ((c = x.getClass()) == String.class)
return c;
// c实现的接口数组不为空
if ((ts = c.getGenericInterfaces()) != null) {
for (int i = 0; i < ts.length; ++i) {
// 判断每个接口t是否为泛型接口，且原始类型为 Comparable，且泛型参数列表长度为 1，且第一个泛型参数为 c
// Comparable<String>
if (((t = ts[i]) instanceof ParameterizedType) &&
((p = (ParameterizedType)t).getRawType() == Comparable.class) &&
(as = p.getActualTypeArguments()) != null && as.length == 1 && as[0] == c)
return c;
}
}
}
return null;
}
// 比较对象大小，无法比较返回0
static int compareComparables(Class<?> kc, Object k, Object x) {
return (x == null || x.getClass() != kc ? 0 :
((Comparable)k).compareTo(x));
}
容量计算方法
// 将传入的大小调整为比 cap 大且是 2 的幂次方的最小整数
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 < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
}
普通方法
构造方法
public HashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal initial capacity: " + initialCapacity);
if (initialCapacity > MAXIMUM_CAPACITY)
initialCapacity = MAXIMUM_CAPACITY;
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new IllegalArgumentException("Illegal load factor: " + loadFactor);
this.loadFactor = loadFactor;
// 向上取整2的N次
this.threshold = tableSizeFor(initialCapacity);
}
public HashMap(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
public HashMap() {
this.loadFactor = DEFAULT_LOAD_FACTOR;
}
public HashMap(Map<? extends K, ? extends V> 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) {
// hashmap尚未初始化，计算容量，对容量阈值赋值
if (table == null) {
float ft = ((float)s / loadFactor) + 1.0F;
int t = ((ft < (float)MAXIMUM_CAPACITY) ?
(int)ft : MAXIMUM_CAPACITY);
if (t > threshold)
threshold = tableSizeFor(t);
}
// 已经初始化且大小不足，进行扩容
else if (s > threshold)
resize();
// 遍历指定 Map 中的每个元素，将其键（key）和值（value）通过调用 putVal 方法放入当前 HashMap 中
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);
}
}
}
获取方法
public V get(Object key) {
Node<K,V> e;
return (e = getNode(hash(key), key)) == null ? null : e.value;
}
final Node<K,V> getNode(int hash, Object key) {
// tab 表示哈希表的数组，first 表示哈希桶中的第一个节点，e 表示遍历哈希桶时的当前节点，n 表示哈希表的长度，k 表示节点的键
Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
// 判断哈希表数组 tab 不为 null、哈希表长度 n 大于 0，并且对应的哈希桶中的第一个节点 first 不为 null
if ((tab = table) != null && (n = tab.length) > 0 && (first = tab[(n - 1) & hash]) != null) {
// 首结点匹配
// 第一个节点 first 的哈希值和给定的哈希值 hash 相等，同时键 key 和节点的键 k 相等（或者都为 null）
if (first.hash == hash && ((k = first.key) == key || (key != null && key.equals(k))))
return first;
if ((e = first.next) != null) {
// 红黑树进行相应的处理
if (first instanceof TreeNode)
return ((TreeNode<K,V>)first).getTreeNode(hash, key);
// 进入一个循环遍历，从第一个节点 first 开始，逐个比较节点的哈希值和键，直到找到匹配的节点或遍历结束
do {
if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k))))
return e;
} while ((e = e.next) != null);
}
}
return null;
}
public boolean containsKey(Object key) {
return getNode(hash(key), key) != null;
}
设置方法
通过方法返回值对key唯一性进行校验
针对已经写入hashmap，可以将旧值重新写入
public V put(K key, V value) {
return putVal(hash(key), key, value, false, true);
}
// 不替换相同的值
public V putIfAbsent(K key, V value) {
return putVal(hash(key), key, value, true, true);
}
// 先添加后扩容
final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
boolean evict) {
Node<K,V>[] tab; Node<K,V> p; int n, i;
// 检查当前的哈希表（table）是否已经存在，如果不存在或长度为0，则进行扩容操作
if ((tab = table) == null || (n = tab.length) == 0)
n = (tab = resize()).length;
// 如果该位置为空，则创建一个新的节点，并将其存放在该位置上
if ((p = tab[i = (n - 1) & hash]) == null)
tab[i] = newNode(hash, key, value, null);
else {
Node<K,V> e; K k;
// 找到了相同的节点(链表头节点)，直接赋值
if (p.hash == hash && ((k = p.key) == key || (key != null && key.equals(k))))
e = p;
// 红黑树进行相应处理
else if (p instanceof TreeNode)
e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
else {
for (int binCount = 0; ; ++binCount) {
// 遍历到链表末尾，则创建一个新的节点并放在链表尾部
if ((e = p.next) == null) {
p.next = newNode(hash, key, value, null);
// 链表长度大于等于8，变为树
if (binCount >= TREEIFY_THRESHOLD - 1)
treeifyBin(tab, hash);
break;
}
// 找到了相同的节点，则直接退出遍历
if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k))))
break;
// 链表移动
p = e;
}
}
// 对存在的相同结点，进行值的替换
if (e != null) {
V oldValue = e.value;
if (!onlyIfAbsent || oldValue == null)
e.value = value;
// 为linkedHshmap设置的方法
afterNodeAccess(e);
return oldValue;
}
}
++modCount;
// 容量大于阈值，扩容
if (++size > threshold)
resize();
afterNodeInsertion(evict);
return null;
}
扩容方法
final Node<K,V>[] resize() {
// 旧hash表
Node<K,V>[] oldTab = table;
// 旧容量 16
int oldCap = (oldTab == null) ? 0 : oldTab.length;
// 旧阈值 12
int oldThr = threshold;
// 新容量，新阈值
int newCap, newThr = 0;
if (oldCap > 0) {
// 旧的数组容量 >0 的情况下
// 旧容量已经达到了最大容量MAXIMUM_CAPACITY，直接设置阈值为Integer.MAX_VALUE，放弃扩容
if (oldCap >= MAXIMUM_CAPACITY) {
threshold = Integer.MAX_VALUE;
return oldTab;
}
// 容量翻一倍且符合条件的情况下 阈值也翻一倍
else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY && oldCap >= DEFAULT_INITIAL_CAPACITY)
newThr = oldThr << 1;
}
// 旧的数组容量 <=0 且旧的阈值 >0，就把新的容量设置成旧的阈值
else if (oldThr > 0)
newCap = oldThr;
// 旧的数组容量 <=0 且旧的阈值 <0，就重新设置新的长度和阈值为默认值
else {
newCap = DEFAULT_INITIAL_CAPACITY;
newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
}
// 新的阈值为0，就重新根据新的容量设置阈值
if (newThr == 0) {
float ft = (float)newCap * loadFactor;
newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ? (int)ft : Integer.MAX_VALUE);
}
// 扩容因子赋值替换
threshold = newThr;
// 根据新的长度初始化新的数组并替换
Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
table = newTab;
if (oldTab != null) {
// 遍历旧的节点数组
for (int j = 0; j < oldCap; ++j) {
Node<K,V> e;
if ((e = oldTab[j]) != null) {
oldTab[j] = null;
// 链表不存在，直接赋值
if (e.next == null)
newTab[e.hash & (newCap - 1)] = e;
// 树节点特殊处理
else if (e instanceof TreeNode)
((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
// 链表结点
else {
// 低位链表：存放在扩容之后的数组的下标位置，与当前数组下标位置一致
// loHead: 低位链表头节点
// loTail: 低位链表尾节点
Node<K,V> loHead = null, loTail = null;
// 高位链表，存放扩容之后的数组的下标位置，原索引+扩容之前数组容量
// hiHead: 高位链表头节点
// hiTail: 高位链表尾节点
Node<K,V> hiHead = null, hiTail = null;
Node<K,V> next;
do {
next = e.next;
// 位置不变
if ((e.hash & oldCap) == 0) {
if (loTail == null)
loHead = e;
else
loTail.next = e;
loTail = e;
}
// 当前位置＋旧容量
else {
if (hiTail == null)
hiHead = e;
else
hiTail.next = e;
hiTail = e;
}
} while ((e = next) != null);
// 转移到新数组
if (loTail != null) {
loTail.next = null;
newTab[j] = loHead;
}
if (hiTail != null) {
hiTail.next = null;
newTab[j + oldCap] = hiHead;
}
}
}
}
}
return newTab;
}
树化方法
final void treeifyBin(Node<K,V>[] tab, int hash) {
int n, index; Node<K,V> e;
// 数组容量小于64，扩容
if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
resize();
// 数组已经初始化且容量大于等于64
else if ((e = tab[index = (n - 1) & hash]) != null) {
// 红黑树的头节点和尾节点指针
TreeNode<K,V> hd = null, tl = null;
do {
// 将槽位第一个元素转化为链表节点
TreeNode<K,V> p = replacementTreeNode(e, null);
// 尾节点为空表示首次进入，将当前结点赋值给头节点
if (tl == null)
hd = p;
// 红黑树已经存在，将当前元素p作为尾结点指向的元素
else {
p.prev = tl;
tl.next = p;
}
// 尾结点更新为最后一个节点
tl = p;
} while ((e = e.next) != null);
// 树化操作
if ((tab[index] = hd) != null)
hd.treeify(tab);
}
}
TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
// next存在
// 1.TreeNode为Node子类
// 2.方便解树
return new TreeNode<>(p.hash, p.key, p.value, next);
}
删除方法
public V remove(Object key) {
Node<K,V> e;
return (e = removeNode(hash(key), key, null, false, true)) == null ? null : e.value;
}
public boolean remove(Object key, Object value) {
return removeNode(hash(key), key, value, true, true) != null;
}
final Node<K,V> removeNode(int hash, Object key, Object value,
boolean matchValue, boolean movable) {
Node<K,V>[] tab; Node<K,V> p; int n, index;
// 数组初始化完成 且 有值 且 该hash位置有值
if ((tab = table) != null && (n = tab.length) > 0 && (p = tab[index = (n - 1) & hash]) != null) {
Node<K,V> node = null, e; K k; V v;
// 第一个节点的哈希值和键与参数hash和key匹配，则将第一个节点p赋值给node
if (p.hash == hash && ((k = p.key) == key || (key != null && key.equals(k))))
node = p;
// 不匹配且存在后续节点
else if ((e = p.next) != null) {
// 树节点查找
if (p instanceof TreeNode)
node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
// 循环遍历节点，匹配到将节点赋值给node
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);
}
}
// 被删除节点已经被找到
if (node != null && (!matchValue || (v = node.value) == value || (value != null && value.equals(v)))) {
if (node instanceof TreeNode)
((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
// 移除头节点，槽位直接指向node的下一个节点
else if (node == p)
tab[index] = node.next;
// 跳过p节点，将p的next指针指向node的下一个节点
else
p.next = node.next;
++modCount;
--size;
afterNodeRemoval(node);
return node;
}
}
return null;
}
清理方法
public void clear() {
Node<K,V>[] tab;
modCount++;
if ((tab = table) != null && size > 0) {
size = 0;
// 清空槽位
for (int i = 0; i < tab.length; ++i)
tab[i] = null;
}
}
存在判断方法
public boolean containsValue(Object value) {
Node<K,V>[] tab; V v;
// 数组已经初始化且存在数据
if ((tab = table) != null && size > 0) {
// 遍历数组
for (int i = 0; i < tab.length; ++i) {
// 遍历节点
for (Node<K,V> e = tab[i]; e != null; e = e.next) {
// 值相同
if ((v = e.value) == value || (value != null && value.equals(v)))
return true;
}
}
}
return false;
}
键集合方法
并未维护一个set集合，而是做了映射处理，keyset相等于hashmap的视图
实现原理：
- 增强for操作基于迭代器实现
- 迭代器iterator()方法依赖于KeyIterator类
- KeyIterator继承HashIterator，返回nextNode().key
- KeyIterator无构造，会调用HashIterator类构造，获取hashmap的table结构
- 调用nextNode().key进一步获取数据
- 其余操作基于hashmap结构实现
- 打印操作默认调用tostring()
- keyset继承AbstractSet继承AbstractCollection的tostring()方法，内部使用迭代器
public Set<K> keySet() {
Set<K> ks = keySet;
if (ks == null) {
ks = new KeySet();
keySet = ks;
}
return 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,V>[] tab;
if (action == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i < tab.length; ++i) {
for (Node<K,V> e = tab[i]; e != null; e = e.next)
action.accept(e.key);
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
}
final class KeyIterator extends HashIterator
implements Iterator<K> {
public final K next() { return nextNode().key; }
}
abstract class HashIterator {
Node<K,V> next; // next entry to return
Node<K,V> current; // current entry
int expectedModCount; // for fast-fail
int index; // current slot
HashIterator() {
expectedModCount = modCount;
Node<K,V>[] t = table;
current = next = null;
index = 0;
if (t != null && size > 0) { // advance to first entry
do {} while (index < t.length && (next = t[index++]) == null);
}
}
public final boolean hasNext() {
return next != null;
}
final Node<K,V> nextNode() {
Node<K,V>[] t;
Node<K,V> e = next;
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
if (e == null)
throw new NoSuchElementException();
// 无后续节点 且 数组存在，进行槽位切换
if ((next = (current = e).next) == null && (t = table) != null) {
do {} while (index < t.length && (next = t[index++]) == null);
}
// 直接链表移动
return e;
}
public final void remove() {
Node<K,V> 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;
}
}
值集合方法
public Collection<V> values() {
Collection<V> vs = values;
if (vs == null) {
vs = new Values();
values = vs;
}
return 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,V>[] tab;
if (action == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i < tab.length; ++i) {
for (Node<K,V> e = tab[i]; e != null; e = e.next)
action.accept(e.value);
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
}
键值对集合
public Set<Map.Entry<K,V>> entrySet() {
Set<Map.Entry<K,V>> es;
return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
}
final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
public final int size() { return size; }
public final void clear() { HashMap.this.clear(); }
public final Iterator<Map.Entry<K,V>> 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,V> 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<K,V>> spliterator() {
return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
}
public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
Node<K,V>[] tab;
if (action == null)
throw new NullPointerException();
if (size > 0 && (tab = table) != null) {
int mc = modCount;
for (int i = 0; i < tab.length; ++i) {
for (Node<K,V> e = tab[i]; e != null; e = e.next)
action.accept(e);
}
if (modCount != mc)
throw new ConcurrentModificationException();
}
}
}
替换方法
public boolean replace(K key, V oldValue, V newValue) {
Node<K,V> e; V v;
// key hash oldValue相同进行替换
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;
}
public V replace(K key, V value) {
Node<K,V> e;
// key hash 相同进行替换
if ((e = getNode(hash(key), key)) != null) {
V oldValue = e.value;
e.value = value;
afterNodeAccess(e);
return oldValue;
}
return null;
}
克隆方法
public Object clone() {
HashMap<K,V> result;
try {
// 浅拷贝
result = (HashMap<K,V>)super.clone();
} catch (CloneNotSupportedException e) {
throw new InternalError(e);
}
result.reinitialize();
result.putMapEntries(this, false);
return result;
}
void reinitialize() {
table = null;
entrySet = null;
keySet = null;
values = null;
modCount = 0;
threshold = 0;
size = 0;
}
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 < (float)MAXIMUM_CAPACITY) ?
(int)ft : MAXIMUM_CAPACITY);
if (t > 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);
}
}
}
序列化方法
private void writeObject(java.io.ObjectOutputStream s)
throws IOException {
int buckets = capacity();
s.defaultWriteObject();
s.writeInt(buckets);
s.writeInt(size);
internalWriteEntries(s);
}
void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
Node<K,V>[] tab;
if (size > 0 && (tab = table) != null) {
// 遍历槽位
for (int i = 0; i < tab.length; ++i) {
// 遍历节点
for (Node<K,V> e = tab[i]; e != null; e = e.next) {
s.writeObject(e.key);
s.writeObject(e.value);
}
}
}
}
private void readObject(java.io.ObjectInputStream s)
throws IOException, ClassNotFoundException {
s.defaultReadObject();
reinitialize();
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new InvalidObjectException("Illegal load factor: " +
loadFactor);
s.readInt();
int mappings = s.readInt();
if (mappings < 0)
throw new InvalidObjectException("Illegal mappings count: " +
mappings);
else if (mappings > 0) {
float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
float fc = (float)mappings / lf + 1.0f;
int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ?
DEFAULT_INITIAL_CAPACITY :
(fc >= MAXIMUM_CAPACITY) ?
MAXIMUM_CAPACITY :
tableSizeFor((int)fc));
float ft = (float)cap * lf;
threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
(int)ft : Integer.MAX_VALUE);
SharedSecrets.getJavaOISAccess().checkArray(s, Map.Entry[].class, cap);
@SuppressWarnings({"rawtypes","unchecked"})
Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
table = tab;
for (int i = 0; i < mappings; i++) {
@SuppressWarnings("unchecked")
K key = (K) s.readObject();
@SuppressWarnings("unchecked")
V value = (V) s.readObject();
// 数据复位
putVal(hash(key), key, value, false, false);
}
}
}
槽点
- 继承
AbstractMap情况下，依旧实现Map接口 - put判断结点是否到8进行扩容时，存在歧义