jdk-HashMap(1.8)源码学习

public static void main(String[] args) throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(2);
        HashMap<Integer,Object> hashMap = new HashMap <>();
        hashMap.put(1,"hong");
// ConcurrentHashMap<String,Object> concurrentHashMap = new ConcurrentHashMap <>();
// concurrentHashMap.put("hong",1);

        new Thread("thread1"){
            @Override
            public void run() {
                hashMap.put(7,"B");
                System.out.println(hashMap);
                countDownLatch.countDown();
            }
        }.start();

        new Thread("thread2"){
            @Override
            public void run() {
                hashMap.put(3,"A");
                System.out.println(hashMap);
                countDownLatch.countDown();
            }
        }.start();

        countDownLatch.await();
        System.out.println(hashMap.toString()+"："+hashMap.size());
    }

{1=hong, 7=B}
{1=hong, 3=A, 7=B}
{1=hong, 3=A, 7=B}：3

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;
}

public V put(K key, V value) {
    //对key做hashcode() 做hash
    return putVal(hash(key), key, value, false, true);
}

final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
               boolean evict) {
    Node<K,V>[] tab; Node<K,V> p; int n, i;
    //table空则创建
    if ((tab = table) == null || (n = tab.length) == 0)
        n = (tab = resize()).length;
    //计算index，并对null做处理 
    if ((p = tab[i = (n - 1) & hash]) == null)
        tab[i] = newNode(hash, key, value, null);
    else {
        Node<K,V> e; K k;
        //节点key存在，直接覆盖value
        if (p.hash == hash &&
            ((k = p.key) == key || (key != null && key.equals(k))))
            e = p;
        //判断该链为红黑树 
        else if (p instanceof TreeNode)
            e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
       //该链为连表 
        else {
            for (int binCount = 0; ; ++binCount) {
                if ((e = p.next) == null) {
                    p.next = newNode(hash, key, value, null);
                    //链表长度大于8转换为红黑树进行处理
                    if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
                        treeifyBin(tab, hash);
                    break;
                }
                //key已经存在直接覆盖value
                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;
    //超过最大容量 就扩容
    if (++size > threshold)
        resize();
    afterNodeInsertion(evict);
    return null;
}

final Node<K,V>[] resize() {
    Node<K,V>[] oldTab = table;
    int oldCap = (oldTab == null) ? 0 : oldTab.length;
    int oldThr = threshold;
    int newCap, newThr = 0;
    if (oldCap > 0) {
        //超过最大值就不再扩容了，就只好随你去碰撞了...
        if (oldCap >= MAXIMUM_CAPACITY) {
            threshold = Integer.MAX_VALUE;
            return oldTab;
        }
        //没超过最大值，就扩充原来的2倍
        else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                 oldCap >= DEFAULT_INITIAL_CAPACITY)
            newThr = oldThr << 1; // double threshold
    }
    //初始化容量
    else if (oldThr > 0) // initial capacity was placed in threshold
        newCap = oldThr;
    else { // zero initial threshold signifies using defaults
    //设置默认值
        newCap = DEFAULT_INITIAL_CAPACITY;
        newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
    }
    
    if (newThr == 0) {
        float ft = (float)newCap * loadFactor;
        newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
                  (int)ft : Integer.MAX_VALUE);
    }
    threshold = newThr;
    @SuppressWarnings({"rawtypes","unchecked"})
        Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
    table = newTab;
    if (oldTab != null) {
        //每个bucket都移动到新的buckets中
        for (int j = 0; j < oldCap; ++j) {
            Node<K,V> 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,V>)e).split(this, newTab, j, oldCap);
                else { // preserve order 链表优化重hash代码块
                    Node<K,V> loHead = null, loTail = null;
                    Node<K,V> hiHead = null, hiTail = null;
                    Node<K,V> next;
                    do {
                        next = e.next;
                        //原索引
                        if ((e.hash & oldCap) == 0) {
                            if (loTail == null)
                                loHead = e;
                            else
                                loTail.next = e;
                            loTail = e;
                        }
                        //原索引+oldCap
                        else {
                            if (hiTail == null)
                                hiHead = e;
                            else
                                hiTail.next = e;
                            hiTail = e;
                        }
                    } while ((e = next) != null);
                    //原索引放到bucket里
                    if (loTail != null) {
                        loTail.next = null;
                        newTab[j] = loHead;
                    }
                    //原索引+oldCap放到bucket里
                    if (hiTail != null) {
                        hiTail.next = null;
                        newTab[j + oldCap] = hiHead;
                    }
                }
            }
        }
    }
    return newTab;
}

//将普通节点转成树节点
final void treeifyBin(Node<K,V>[] tab, int hash) {
    int n, index; Node<K,V> e;
    if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
        resize();
    else if ((e = tab[index = (n - 1) & hash]) != null) {
        TreeNode<K,V> hd = null, tl = null;
        do {
            TreeNode<K,V> 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);
    }
}

//将树节点转成红黑树
final void treeify(Node<K,V>[] tab) {
    //根节点
    TreeNode<K,V> root = null;
    for (TreeNode<K,V> x = this, next; x != null; x = next) {
        next = (TreeNode<K,V>)x.next;
        x.left = x.right = null;
        //如果根节点为空，根节点为黑色
        if (root == null) {
            x.parent = null;
            x.red = false;
            root = x;
        }
        else {
            K k = x.key;
            int h = x.hash;
            //key 所属class
            Class<?> kc = null;
            for (TreeNode<K,V> p = root;;) {
                //dir 标识方向 等于-1时向左子树走 等于1时向右子树走 当前的key为hash值
                int dir, ph;
                K pk = p.key;
                //判断下一个节点小于当前节点时 向左走
                if ((ph = p.hash) > h)
                    //向左子数走标识
                    dir = -1;
                else if (ph < h)
                    //向右子数走标识
                    dir = 1;
                else if ((kc == null &&
                          (kc = comparableClassFor(k)) == null) ||
                         (dir = compareComparables(kc, k, pk)) == 0)
                    dir = tieBreakOrder(k, pk);

                TreeNode<K,V> xp = p;
                if ((p = (dir <= 0) ? p.left : p.right) == null) {
                    x.parent = xp;
                    if (dir <= 0)
                        xp.left = x;
                    else
                        xp.right = x;
                    root = balanceInsertion(root, x);
                    break;
                }
            }
        }
    }
    moveRootToFront(tab, root);
}

package java.util;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;
import sun.misc.SharedSecrets;

//hashmap源码实现 默认继承AbstractMap 实现map
public class HashMap<K,V> extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable {

    private static final long serialVersionUID = 362498820763181265L;



    //Hash表默认初始容量
    static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

    //最大Hash表容量
    static final int MAXIMUM_CAPACITY = 1 << 30;

    //负载因子 0.75
    static final float DEFAULT_LOAD_FACTOR = 0.75f;

    //链表转红黑树阈值
    static final int TREEIFY_THRESHOLD = 8;

    //红黑树转链表阈值
    static final int UNTREEIFY_THRESHOLD = 6;

   //链表转红黑树时hash表最小容量阈值，达不到优先扩容。
    static final int MIN_TREEIFY_CAPACITY = 64;

    //基本hash的node节点
    static class Node<K,V> implements Map.Entry<K,V> {
        //当前节点hash值
        final int hash;
        //当前节点key
        final K key;
        //当前节点内容
        V value;
        //下一个节点
        Node<K,V> next;
        //构造方法
        Node(int hash, K key, V value, Node<K,V> next) {
            this.hash = hash;
            this.key = key;
            this.value = value;
            this.next = next;
        }
        //获取当前key
        public final K getKey()        { return key; }
        //获取当前value
        public final V getValue()      { return value; }
        //转字符串方法
        public final String toString() { return key + "=" + value; }
        //获取hashcode方法
        public final int hashCode() {
            return Objects.hashCode(key) ^ Objects.hashCode(value);
        }
        //赋值方法返回旧值
        public final V setValue(V newValue) {
            V oldValue = value;
            value = newValue;
            return oldValue;
        }
        //判断当前对象是否在hash中 如果要存在返回true
        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;
        }
    }

    //生成hash的方法（每次添加时都会调用，获取所在位置）
    static final int hash(Object key) {
        int h;
        //为空返回0不为空先获取当前的hashCode然后^向右移16位生成一个hashCode(也可能重)
        return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
    }

    //判断当前是否Comparable实现，如果是返回，不是返回空
    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 < ts.length; ++i) {
                    if (((t = ts[i]) instanceof ParameterizedType) &&
                        ((p = (ParameterizedType)t).getRawType() ==
                         Comparable.class) &&
                        (as = p.getActualTypeArguments()) != null &&
                        as.length == 1 && as[0] == c) // type arg is c
                        return c;
                }
            }
        }
        return null;
    }

    //如果class是compare类型的则返回对比结果。
    @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable
    static int compareComparables(Class<?> kc, Object k, Object x) {
        return (x == null || x.getClass() != kc ? 0 :
                ((Comparable)k).compareTo(x));
    }

    //给定目标容量大小的（总是2的幂次方）（最小为）
    //小于8默认返回8 大于8小于16返回16 大于16小于32则为32这样是2的幂次方。
    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;
    }

    /* ---------------- Fields -------------- */

    //存放数据表的列表
    transient Node<K,V>[] table;

    //保存缓存的entryset
    transient Set<Map.Entry<K,V>> entrySet;

   //队列长度
    transient int size;

    //被修改的次数（用于快速失败）
    transient int modCount;

    /**
     * The next size value at which to resize (capacity * load factor).
     *
     * @serial
     */
    //临界值，作用扩容使用判断 临界值=负载因子*容量
    int threshold;

    //负载因子 默认为0.75
    final float loadFactor;

    /* ---------------- Public operations -------------- */

    //hashmap的构建方法
    //initialCapacity 初始容量
    //loadFactor 负载因子
    public HashMap(int initialCapacity, float loadFactor) {
        //小于0则抛出异常
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal initial capacity: " +
                                               initialCapacity);
        //最大不超过默认值
        if (initialCapacity > MAXIMUM_CAPACITY)
            initialCapacity = MAXIMUM_CAPACITY;
        //小于等于0或类型不是float则抛出异常
        if (loadFactor <= 0 || Float.isNaN(loadFactor))
            throw new IllegalArgumentException("Illegal load factor: " +
                                               loadFactor);
        //负载因子
        this.loadFactor = loadFactor;
        //初始化容量
        this.threshold = tableSizeFor(initialCapacity);
    }

    //构造方法 带初始负载因子
    public HashMap(int initialCapacity) {
        this(initialCapacity, DEFAULT_LOAD_FACTOR);
    }

    //不带参数的默认构造方法
    public HashMap() {
        this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
    }

    //带初始值的构造方法
    public HashMap(Map<? extends K, ? extends V> m) {
        this.loadFactor = DEFAULT_LOAD_FACTOR;
        putMapEntries(m, false);
    }

    //添加元素
    final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
        //获取map的数量
        int s = m.size();
        //数量大于0个
        if (s > 0) {
            //如果表为空 则进行初始化
            if (table == null) { // pre-size
                //计算出容量 注意这里+1为向上取整，保证是2的倍数。
                float ft = ((float)s / loadFactor) + 1.0F;
                //如果大于最大容量则取最大，否则取本身
                int t = ((ft < (float)MAXIMUM_CAPACITY) ?
                         (int)ft : MAXIMUM_CAPACITY);
                //只有t大于暂存容量才会进行扩容
                if (t > threshold)
                    threshold = tableSizeFor(t);
            }
            //如果s大于暂存容易那么先扩容（本来就不够）
            else if (s > threshold)
                resize();
            //最后循环添加内容入列表值中（中间可能也会扩容）
            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);
            }
        }
    }

    //返回当前列表长度
    public int size() {
        return size;
    }

    //判断是否为空 如果长度为0则为true 否则为false
    public boolean isEmpty() {
        return size == 0;
    }

    //获取指定的key是否在队列中，存在返回内容否则返回空
    public V get(Object key) {
        Node<K,V> e;
        //hash(key)计算hashcode值，getNode获取这个key是否存在
        //最后赋值给e，再判断为空，最后返回空或e.value的值;
        return (e = getNode(hash(key), key)) == null ? null : e.value;
    }

    //通过hash和key获取返回值，如果没有返回Null
    final Node<K,V> getNode(int hash, Object key) {
        //tab 用于复制table的数据（临时）
        //first 为tab[(n - 1) & hash]) 的数据
        //n 为tab.length的总长度
        //k 为first.key 用于判断是否为传进来的Key一致
        Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
        //判断列表不为空 并且长度大于0 且 倒数第一个节点不为空
        if ((tab = table) != null && (n = tab.length) > 0 &&
            (first = tab[(n - 1) & hash]) != null) {
            //如果倒数第一个节点的hash为传入来的hash且 key也相同那么就返回这个节点（找到了）
            if (first.hash == hash && // always check first node
                ((k = first.key) == key || (key != null && key.equals(k))))
                return first;
             //如果找不到则继续往上找
            if ((e = first.next) != null) {
                //判断类型是否为TreeNode
                if (first instanceof TreeNode)
                    //返回上一个节点
                    return ((TreeNode<K,V>)first).getTreeNode(hash, key);
                do {
                    //如果倒数第一个节点的hash为传入来的hash且 key也相同那么就返回这个节点（找到了）
                    if (e.hash == hash &&
                        ((k = e.key) == key || (key != null && key.equals(k))))
                        return e;
                 //下一节点不为空
                } while ((e = e.next) != null);
            }
        }
        return null;
    }

    //判断是否包含节点，如果存在返回true 否则返回false
    public boolean containsKey(Object key) {
        return getNode(hash(key), key) != null;
    }

    //添加方法
    public V put(K key, V value) {
        //添加到val
        return putVal(hash(key), key, value, false, true);
    }

    //添加方法
    final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
                   boolean evict) {
        //tab用来复制列表内容
        //p 获取最后一位
        //n 获取当前队列长度
        //i 队列长度-1
        Node<K,V>[] tab; Node<K,V> p; int n, i;
        //如果列表为空 或 列表的长度为0
        if ((tab = table) == null || (n = tab.length) == 0)
            //初始化表格
            n = (tab = resize()).length;
        //如果最后一位为空
        if ((p = tab[i = (n - 1) & hash]) == null)
            //创建新节点赋给最后一个节点
            tab[i] = newNode(hash, key, value, null);
        else {
            Node<K,V> e; K k;
            //最后一位的哈希==传进来的hash且key相同
            if (p.hash == hash &&
                ((k = p.key) == key || (key != null && key.equals(k))))
                //将最后一位赋给e
                e = p;
            //如果 p的节点为树节点类型
            else if (p instanceof TreeNode)
                //调用添加树节点添加方法（详细看方法）
                e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
            else {
                //如果不是树节点是链表
                for (int binCount = 0; ; ++binCount) {
                    //如果下一节点为空
                    if ((e = p.next) == null) {
                        //创建新节点并将p.next指向它（末尾）
                        p.next = newNode(hash, key, value, null);
                        //遍历过程中 binCount大于等于7，那么会进行红默数转换（如果太小会进行扩容 **** 核心）
                        if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
                            treeifyBin(tab, hash);
                        break;
                    }
                    //如果下一节点不为空 且 hash等于e.hash而且key也相同那么证明赋过了（并发解决）直接结束
                    if (e.hash == hash &&
                        ((k = e.key) == key || (key != null && key.equals(k))))
                        break;
                    //如果没有就直接将e赋给p
                    p = e;
                }
            }
            //e不为空（节点已存在）
            if (e != null) { // existing mapping for key
                //获取e的内容
                V oldValue = e.value;
                //如果onlyIfAbsent为false或oldValue为空
                if (!onlyIfAbsent || oldValue == null)
                    //将传进来的值赋给e.value
                    e.value = value;
                //空方法（留给下级实现）
                afterNodeAccess(e);
                //返回旧值
                return oldValue;
            }
        }
        //被修改次数+1
        ++modCount;
        //判断是否需要扩容
        if (++size > threshold)
            //进行扩容
            resize();
        //空实现
        afterNodeInsertion(evict);
        //返回空
        return null;
    }

    //扩容实现方法
    final Node<K,V>[] resize() {
        //获取当前列表
        Node<K,V>[] oldTab = table;
        //如果当前表为空那么为0或获取表的长度
        int oldCap = (oldTab == null) ? 0 : oldTab.length;
        //获取临界值
        int oldThr = threshold;
        //新容量（扩容2倍）
        int newCap, newThr = 0;
        if (oldCap > 0) {
            if (oldCap >= MAXIMUM_CAPACITY) {
                threshold = Integer.MAX_VALUE;
                return oldTab;
            }
            //扩容两倍小于最大值 且 表长度大于等于初始容量
            else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                     oldCap >= DEFAULT_INITIAL_CAPACITY)
                //新临界值=旧临界值扩容2倍
                newThr = oldThr << 1; // double threshold
        }
        //如果旧临界值大于0
        else if (oldThr > 0) // initial capacity was placed in threshold
            //新容量等于临界值
            newCap = oldThr;
        else { // zero initial threshold signifies using defaults
            //新容量等于初始默认值
            newCap = DEFAULT_INITIAL_CAPACITY;
            //计算新的临界值
            newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
        }
        //临界值为0
        if (newThr == 0) {
            //重新计算临界值
            float ft = (float)newCap * loadFactor;
            //如果超过最大则用最大临界值，否则用计算出来的值
            newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
                      (int)ft : Integer.MAX_VALUE);
        }
        //将新的临界值赋给全局
        threshold = newThr;
        @SuppressWarnings({"rawtypes","unchecked"})
        //新表等于新的初始化
        Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
        table = newTab;
        //如果旧值不为空 进行循环的赋给新表，进行全数迁移
        if (oldTab != null) {
            //迁移旧数据到新表中
            for (int j = 0; j < oldCap; ++j) {
                Node<K,V> e;
                //不为空进行赋值
                if ((e = oldTab[j]) != null) {
                    //将旧表所在位置赋空
                    oldTab[j] = null;
                    //如果链表只有一个值，直接新一个新node
                    if (e.next == null)
                        //所给所在位置
                        newTab[e.hash & (newCap - 1)] = e;
                    //如果为树节点
                    else if (e instanceof TreeNode)
                        //分割树，将新表和旧表分害成两个树，会判断是否需要转换成红默数存入新表
                        ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
                    else { // preserve order
                        //低位的hash链表（旧位置）
                        Node<K,V> loHead = null, loTail = null;
                        //高位的hash链表(新位置)
                        Node<K,V> hiHead = null, hiTail = null;
                        //下一个节点
                        Node<K,V> next;
                        //循环处理
                        do {
                            //获取下一个节点
                            next = e.next;
                            //通过hash&老数据长度如果为0 保持位置不变
                            if ((e.hash & oldCap) == 0) {
                                //如果为空保持原位置不动
                                if (loTail == null)
                                    //记住头部
                                    loHead = e;
                                else
                                    //赋值给低位
                                    loTail.next = e;
                                loTail = e;
                            }
                            //放到新链表中
                            else {
                                if (hiTail == null)
                                    //设置表头
                                    hiHead = e;
                                else
                                    hiTail.next = e;
                                hiTail = e;
                            }
                        } while ((e = next) != null);
                        //将分组后的链表映射到新表中
                        if (loTail != null) {
                            loTail.next = null;
                            //原索引不变
                            newTab[j] = loHead;
                        }
                        if (hiTail != null) {
                            hiTail.next = null;
                            //需要移到新的索引，位置是 j+oldCap
                            newTab[j + oldCap] = hiHead;
                        }
                    }
                }
            }
        }
        //返回新表
        return newTab;
    }

    //将链表转为红黑树方法
    final void treeifyBin(Node<K,V>[] tab, int hash) {
        //n为列表的长度
        //index最后一位的下标
        //e最后一个节点
        int n, index; Node<K,V> e;
        //表为空 或长度小于初始容易进行初始化（扩容）
        if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
            resize();
        //如果最后一位不为空
        else if ((e = tab[index = (n - 1) & hash]) != null) {
            //hd队头 tl队尾
            TreeNode<K,V> hd = null, tl = null;
            //循环
            do {
                //新建一个树形节点，内空就是当前e
                TreeNode<K,V> p = replacementTreeNode(e, null);
                //队尾为空
                if (tl == null)
                    //将p赋给队头
                    hd = p;
                else {
                    //将p的队头指向tl
                    p.prev = tl;
                    //将tl的下一个节点指定p
                    tl.next = p;
                }
                //将新建的p赋给队头
                tl = p;
             //判断e的下一个节点不为空才循环（从头到尾循环）
            } while ((e = e.next) != null);
            //将组建好的链表赋给队列最后一个
            if ((tab[index] = hd) != null)
                //将该节点转成红黑树
                hd.treeify(tab);
        }
    }

    //添加多个元素方法
    public void putAll(Map<? extends K, ? extends V> m) {
        putMapEntries(m, true);
    }

    //删除指定Key方法
    public V remove(Object key) {
        Node<K,V> e;
        return (e = removeNode(hash(key), key, null, false, true)) == null ?
            null : e.value;
    }

    //删除指定key
    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;
        //表不为空且表的长度大于0且最后一个节点不为空
        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;
            //匹配hash地址的第一个节点是否匹配，hash和key都匹配，则是要删除的元素
            if (p.hash == hash &&
                ((k = p.key) == key || (key != null && key.equals(k))))
                node = p;
            //下一个节点不为空
            else if ((e = p.next) != null) {
                //判断是否为红黑树
                if (p instanceof TreeNode)
                    node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
                else {
                    //遍历链表
                    do {
                        //如果hash、key 相同 则
                        if (e.hash == hash &&
                            ((k = e.key) == key ||
                             (key != null && key.equals(k)))) {
                            node = e;
                            break;
                        }
                        p = e;
                    } while ((e = e.next) != null);
                }
            }
            //node不为空 且 matchvalue为false 或者 内容一致
            if (node != null && (!matchValue || (v = node.value) == value ||
                                 (value != null && value.equals(v)))) {
                //判断是否为树节点，则是删除
                if (node instanceof TreeNode)
                    ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
                //node为p进行赋值
                else if (node == p)
                    tab[index] = node.next;
                else
                    //最后获取最后一个节点
                    p.next = node.next;
                //节点自增
                ++modCount;
                //数量减1
                --size;
                afterNodeRemoval(node);
                //返回节点
                return node;
            }
        }
        //返回空（找不到）
        return null;
    }

    //清空列表
    public void clear() {
        Node<K,V>[] tab;
        modCount++;
        if ((tab = table) != null && size > 0) {
            size = 0;
            for (int i = 0; i < tab.length; ++i)
                tab[i] = null;
        }
    }

    //判断是否包含该内容
    public boolean containsValue(Object value) {
        Node<K,V>[] tab; V v;
        if ((tab = table) != null && size > 0) {
            for (int i = 0; i < tab.length; ++i) {
                for (Node<K,V> e = tab[i]; e != null; e = e.next) {
                    if ((v = e.value) == value ||
                        (value != null && value.equals(v)))
                        return true;
                }
            }
        }
        return false;
    }

    //将列表转成列表
    public Set<K> keySet() {
        Set<K> ks = keySet;
        if (ks == null) {
            ks = new KeySet();
            keySet = ks;
        }
        return ks;
    }
    //抽象set实现
    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();
            }
        }
    }

    //获取所有的内容集合列表
    public Collection<V> values() {
        Collection<V> vs = values;
        if (vs == null) {
            vs = new Values();
            values = vs;
        }
        return vs;
    }
    //values的抽象实现
    final class Values extends AbstractCollection<V> {
        //返回数量
        public final int size()                 { return size; }
        //清空方法
        public final void clear()               { HashMap.this.clear(); }
        //迭代器方法
        public final Iterator<V> iterator()     { return new ValueIterator(); }
        //判断是否包含
        public final boolean contains(Object o) { return containsValue(o); }
        public final Spliterator<V> spliterator() {
            return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
        }
        //循环检查
        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();
            }
        }
    }

    //将hash转成set列表的方法
    public Set<Map.Entry<K,V>> entrySet() {
        Set<Map.Entry<K,V>> es;
        return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
    }
    //entryset抽象实现
    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();
        }
        //判断是否包含方法
        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);
        }
        //删除方法
        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();
            }
        }
    }

    //获取key如果为空返回默认值
    @Override
    public V getOrDefault(Object key, V defaultValue) {
        Node<K,V> e;
        return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
    }
    //添加方法
    @Override
    public V putIfAbsent(K key, V value) {
        return putVal(hash(key), key, value, true, true);
    }
    //删除谅支
    @Override
    public boolean remove(Object key, Object value) {
        return removeNode(hash(key), key, value, true, true) != null;
    }
    //替换方法
    //将 oldValue替换为newValue
    @Override
    public boolean replace(K key, V oldValue, V newValue) {
        Node<K,V> e; V v;
        //获取key不为空 且oldValue等于这个对象的值
        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;
    }
    //替换内容
    @Override
    public V replace(K key, V value) {
        Node<K,V> 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) {
        //如果为空跑出异常
        if (mappingFunction == null)
            throw new NullPointerException();
        //计算hash值
        int hash = hash(key);
        Node<K,V>[] tab; Node<K,V> first; int n, i;
        int binCount = 0;
        TreeNode<K,V> t = null;
        Node<K,V> old = null;
        //如果 size大于threshold 或表为空
        if (size > threshold || (tab = table) == null ||
            (n = tab.length) == 0)
            //tab进行初始化并获取长度给n
            n = (tab = resize()).length;
        //如果first 等于最后一个节点 不为空
        if ((first = tab[i = (n - 1) & hash]) != null) {
            //判断为TreeNode类型 进行
            if (first instanceof TreeNode)
                //获取取根节点
                old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
            else {
                //不为treeNode则进行循环判断
                Node<K,V> 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);
            }
            //旧值
            V oldValue;
            //如果旧值相同则直接返回
            if (old != null && (oldValue = old.value) != null) {
                afterNodeAccess(old);
                return oldValue;
            }
        }
        //获取key对应的值
        V v = mappingFunction.apply(key);
        //空直接返回
        if (v == null) {
            return null;
        //不为空
        } else if (old != null) {
            //将v赋给old的value并返回
            old.value = v;
            afterNodeAccess(old);
            return v;
        }
        //如果 t不为空
        else if (t != null)
            //添加到树中
            t.putTreeVal(this, tab, hash, key, v);
        else {
            //如果都不是 则创建一个新节点放到最后一个位置
            tab[i] = newNode(hash, key, v, first);
            //如果7则进行红黑树转换
            if (binCount >= TREEIFY_THRESHOLD - 1)
                treeifyBin(tab, hash);
        }
        //自增
        ++modCount;
        ++size;
        afterNodeInsertion(true);
        //最终返回v
        return v;
    }
    //指定的key不为空返回key的内容，如果为空则删除这个位置并返回空
    public V computeIfPresent(K key,
                              BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
        if (remappingFunction == null)
            throw new NullPointerException();
        Node<K,V> 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;
    }
    //同上类似
    @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,V>[] tab; Node<K,V> first; int n, i;
        int binCount = 0;
        TreeNode<K,V> t = null;
        Node<K,V> 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,V>)first).getTreeNode(hash, key);
            else {
                Node<K,V> 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;
    }
    //合并hash列表
    @Override
    public V merge(K key, V value,
                   BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
        //value为空抛出异常
        if (value == null)
            throw new NullPointerException();
        //remappingFunction为空抛出异常
        if (remappingFunction == null)
            throw new NullPointerException();
        int hash = hash(key);
        Node<K,V>[] tab; Node<K,V> first; int n, i;
        int binCount = 0;
        TreeNode<K,V> t = null;
        Node<K,V> old = null;
        //如果大于临界值 或表为空 则进行扩容或初始化
        if (size > threshold || (tab = table) == null ||
            (n = tab.length) == 0)
            n = (tab = resize()).length;
        //first为找到的具体位置 如果不为空（证明有值了）
        if ((first = tab[i = (n - 1) & hash]) != null) {
            //判断类型
            if (first instanceof TreeNode)
                //获取旧值
                old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
            else {
                //如果类型不是treeNode 进行循环匹配
                Node<K,V> e = first; K k;
                do {
                    //hash一致且key一致 那么将这个e赋给旧值替换掉
                    if (e.hash == hash &&
                        ((k = e.key) == key || (key != null && key.equals(k)))) {
                        old = e;
                        break;
                    }
                    //自增
                    ++binCount;
                } while ((e = e.next) != null);
            }
        }
        //如果old不为空
        if (old != null) {
            V v;
            //old的内容不为空
            if (old.value != null)
                //进行替换旧值
                v = remappingFunction.apply(old.value, value);
            else
                //直接将新值赋上
                v = value;
            if (v != null) {
                //重新赋值
                old.value = v;
                afterNodeAccess(old);
            }
            else
                //还是为空的话就把这个节点干掉
                removeNode(hash, key, null, false, true);
            //返回这个v
            return v;
        }
        //判断value不为空
        if (value != null) {
            //并且t不为空
            if (t != null)
                //添加到节点中
                t.putTreeVal(this, tab, hash, key, value);
            else {
                //创建新节点并赋给表的指定位置
                tab[i] = newNode(hash, key, value, first);
                //判断是否需要转换红黑树
                if (binCount >= TREEIFY_THRESHOLD - 1)
                    treeifyBin(tab, hash);
            }
            //自增
            ++modCount;
            ++size;
            afterNodeInsertion(true);
        }
        //返回值
        return value;
    }
    //循环的实现方法
    @Override
    public void forEach(BiConsumer<? super K, ? 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.key, e.value);
            }
            if (modCount != mc)
                throw new ConcurrentModificationException();
        }
    }
    //缓存所有的方法实现
    @Override
    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
        Node<K,V>[] tab;
        //如果方法为空直接抛出异常
        if (function == null)
            throw new NullPointerException();
        //判断表有值
        if (size > 0 && (tab = table) != null) {
            //获取修改次数
            int mc = modCount;
            //表长度
            for (int i = 0; i < tab.length; ++i) {
                //通过循环替换value值
                for (Node<K,V> e = tab[i]; e != null; e = e.next) {
                    e.value = function.apply(e.key, e.value);
                }
            }
            //如果数量不一致直接抛出异常（必须保证全部成功或失败）
            if (modCount != mc)
                throw new ConcurrentModificationException();
        }
    }

    /* ------------------------------------------------------------ */
    // Cloning and serialization

    //复制的方法
    @SuppressWarnings("unchecked")
    @Override
    public Object clone() {
        HashMap<K,V> result;
        try {
            result = (HashMap<K,V>)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;
    }

    //获取负载因子方法
    final float loadFactor() { return loadFactor; }
    //获取当前使用容量
    final int capacity() {
        return (table != null) ? table.length :
            (threshold > 0) ? threshold :
            DEFAULT_INITIAL_CAPACITY;
    }

    //写对象
    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);
    }

    //读取象
    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 || Float.isNaN(loadFactor))
            throw new InvalidObjectException("Illegal load factor: " +
                                             loadFactor);
        s.readInt(); // Read and ignore number of buckets
        int mappings = s.readInt(); // Read number of mappings (size)
        if (mappings < 0)
            throw new InvalidObjectException("Illegal mappings count: " +
                                             mappings);
        else if (mappings > 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 < 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);

            // Check Map.Entry[].class since it's the nearest public type to
            // what we're actually creating.
            SharedSecrets.getJavaOISAccess().checkArray(s, Map.Entry[].class, cap);
            @SuppressWarnings({"rawtypes","unchecked"})
            Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
            table = tab;

            // Read the keys and values, and put the mappings in the HashMap
            for (int i = 0; i < mappings; i++) {
                @SuppressWarnings("unchecked")
                    K key = (K) s.readObject();
                @SuppressWarnings("unchecked")
                    V value = (V) s.readObject();
                putVal(hash(key), key, value, false, false);
            }
        }
    }

    //抽象迭代器
    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();
            if ((next = (current = e).next) == null && (t = table) != null) {
                do {} while (index < t.length && (next = t[index++]) == null);
            }
            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;
        }
    }

    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<K,V>> {
        public final Map.Entry<K,V> next() { return nextNode(); }
    }

    //分割器
    static class HashMapSpliterator<K,V> {
        final HashMap<K,V> map;
        Node<K,V> current; // 当前节点
        int index; // 当前节点下标
        int fence; // 最后一个下标
        int est; // 当前数量
        int expectedModCount; // 用于检查
        //构造方法
        HashMapSpliterator(HashMap<K,V> m, int origin,
                           int fence, int est,
                           int expectedModCount) {
            this.map = m;
            this.index = origin;
            this.fence = fence;
            this.est = est;
            this.expectedModCount = expectedModCount;
        }
        //初始化使用到的（最后一个下标）
        final int getFence() { // initialize fence and size on first use
            int hi;
            if ((hi = fence) < 0) {
                HashMap<K,V> m = map;
                est = m.size;
                expectedModCount = m.modCount;
                Node<K,V>[] tab = m.table;
                hi = fence = (tab == null) ? 0 : tab.length;
            }
            return hi;
        }
        //获取当前数量
        public final long estimateSize() {
            getFence(); // force init
            return (long) est;
        }
    }
    //静态 key的分割类
    static final class KeySpliterator<K,V>
        extends HashMapSpliterator<K,V>
        implements Spliterator<K> {
        KeySpliterator(HashMap<K,V> m, int origin, int fence, int est,
                       int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public KeySpliterator<K,V> trySplit() {
            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid || current != null) ? null :
                new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
                                        expectedModCount);
        }
        //同上类似
        public void forEachRemaining(Consumer<? super K> action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap<K,V> m = map;
            Node<K,V>[] tab = m.table;
            if ((hi = fence) < 0) {
                mc = expectedModCount = m.modCount;
                hi = fence = (tab == null) ? 0 : tab.length;
            }
            else
                mc = expectedModCount;
            if (tab != null && tab.length >= hi &&
                (i = index) >= 0 && (i < (index = hi) || current != null)) {
                Node<K,V> p = current;
                current = null;
                do {
                    if (p == null)
                        p = tab[i++];
                    else {
                        action.accept(p.key);
                        p = p.next;
                    }
                } while (p != null || i < hi);
                if (m.modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
        //尝试提交操作
        public boolean tryAdvance(Consumer<? super K> action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node<K,V>[] tab = map.table;
            if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                while (current != null || index < hi) {
                    if (current == null)
                        current = tab[index++];
                    else {
                        K k = current.key;
                        current = current.next;
                        action.accept(k);
                        if (map.modCount != expectedModCount)
                            throw new ConcurrentModificationException();
                        return true;
                    }
                }
            }
            return false;
        }
        //返回当前数组数量
        public int characteristics() {
            return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
                Spliterator.DISTINCT;
        }
    }
    //内容分割类
    static final class ValueSpliterator<K,V>
        extends HashMapSpliterator<K,V>
        implements Spliterator<V> {
        ValueSpliterator(HashMap<K,V> m, int origin, int fence, int est,
                         int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public ValueSpliterator<K,V> trySplit() {
            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid || 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,V> m = map;
            Node<K,V>[] tab = m.table;
            if ((hi = fence) < 0) {
                mc = expectedModCount = m.modCount;
                hi = fence = (tab == null) ? 0 : tab.length;
            }
            else
                mc = expectedModCount;
            if (tab != null && tab.length >= hi &&
                (i = index) >= 0 && (i < (index = hi) || current != null)) {
                Node<K,V> p = current;
                current = null;
                do {
                    if (p == null)
                        p = tab[i++];
                    else {
                        action.accept(p.value);
                        p = p.next;
                    }
                } while (p != null || i < hi);
                if (m.modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        public boolean tryAdvance(Consumer<? super V> action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node<K,V>[] tab = map.table;
            if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                while (current != null || index < hi) {
                    if (current == null)
                        current = tab[index++];
                    else {
                        V v = current.value;
                        current = current.next;
                        action.accept(v);
                        if (map.modCount != expectedModCount)
                            throw new ConcurrentModificationException();
                        return true;
                    }
                }
            }
            return false;
        }

        public int characteristics() {
            return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
        }
    }
    //实体分割迭代器
    static final class EntrySpliterator<K,V>
        extends HashMapSpliterator<K,V>
        implements Spliterator<Map.Entry<K,V>> {
        EntrySpliterator(HashMap<K,V> m, int origin, int fence, int est,
                         int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public EntrySpliterator<K,V> trySplit() {
            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid || current != null) ? null :
                new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
                                          expectedModCount);
        }

        public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap<K,V> m = map;
            Node<K,V>[] tab = m.table;
            if ((hi = fence) < 0) {
                mc = expectedModCount = m.modCount;
                hi = fence = (tab == null) ? 0 : tab.length;
            }
            else
                mc = expectedModCount;
            if (tab != null && tab.length >= hi &&
                (i = index) >= 0 && (i < (index = hi) || current != null)) {
                Node<K,V> p = current;
                current = null;
                do {
                    if (p == null)
                        p = tab[i++];
                    else {
                        action.accept(p);
                        p = p.next;
                    }
                } while (p != null || i < hi);
                if (m.modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node<K,V>[] tab = map.table;
            if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                while (current != null || index < hi) {
                    if (current == null)
                        current = tab[index++];
                    else {
                        Node<K,V> e = current;
                        current = current.next;
                        action.accept(e);
                        if (map.modCount != expectedModCount)
                            throw new ConcurrentModificationException();
                        return true;
                    }
                }
            }
            return false;
        }

        public int characteristics() {
            return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
                Spliterator.DISTINCT;
        }
    }


    //创建新节点方法
    Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
        return new Node<>(hash, key, value, next);
    }

    // 获取新节点方法
    Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
        return new Node<>(p.hash, p.key, p.value, next);
    }

    // 创建新节点方法
    TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
        return new TreeNode<>(hash, key, value, next);
    }

    // For treeifyBin
    TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
        return new TreeNode<>(p.hash, p.key, p.value, next);
    }

    //初始化方法
    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,V> p) { }
    void afterNodeInsertion(boolean evict) { }
    void afterNodeRemoval(Node<K,V> p) { }

    void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
        Node<K,V>[] tab;
        if (size > 0 && (tab = table) != null) {
            for (int i = 0; i < tab.length; ++i) {
                for (Node<K,V> e = tab[i]; e != null; e = e.next) {
                    s.writeObject(e.key);
                    s.writeObject(e.value);
                }
            }
        }
    }

    /* ------------------------------------------------------------ */
    // Tree bins

    //树节点类实现（红黑）
    static final class TreeNode<K,V> extends LinkedHashMap.Entry<K,V> {
        //红黑树父类
        TreeNode<K,V> parent; // red-black tree links
        //左边
        TreeNode<K,V> left;
        //右边
        TreeNode<K,V> right;
        //上一个节点
        TreeNode<K,V> prev; // needed to unlink next upon deletion
        //是否为红
        boolean red;
        //构造方法
        TreeNode(int hash, K key, V val, Node<K,V> next) {
            super(hash, key, val, next);
        }

        //获取根节点
        final TreeNode<K,V> root() {
            for (TreeNode<K,V> r = this, p;;) {
                if ((p = r.parent) == null)
                    return r;
                r = p;
            }
        }

        //确保根为第一个节点
        static <K,V> void moveRootToFront(Node<K,V>[] tab, TreeNode<K,V> root) {
            int n;
            if (root != null && tab != null && (n = tab.length) > 0) {
                int index = (n - 1) & root.hash;
                TreeNode<K,V> first = (TreeNode<K,V>)tab[index];
                if (root != first) {
                    Node<K,V> rn;
                    tab[index] = root;
                    TreeNode<K,V> rp = root.prev;
                    if ((rn = root.next) != null)
                        ((TreeNode<K,V>)rn).prev = rp;
                    if (rp != null)
                        rp.next = rn;
                    if (first != null)
                        first.prev = root;
                    root.next = first;
                    root.prev = null;
                }
                assert checkInvariants(root);
            }
        }

        //通过key
        final TreeNode<K,V> find(int h, Object k, Class<?> kc) {
            TreeNode<K,V> p = this;
            do {
                int ph, dir; K pk;
                TreeNode<K,V> pl = p.left, pr = p.right, q;
                if ((ph = p.hash) > h)
                    p = pl;
                else if (ph < h)
                    p = pr;
                else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                    return p;
                else if (pl == null)
                    p = pr;
                else if (pr == null)
                    p = pl;
                else if ((kc != null ||
                          (kc = comparableClassFor(k)) != null) &&
                         (dir = compareComparables(kc, k, pk)) != 0)
                    p = (dir < 0) ? pl : pr;
                else if ((q = pr.find(h, k, kc)) != null)
                    return q;
                else
                    p = pl;
            } while (p != null);
            return null;
        }

        //查找根节点
        final TreeNode<K,V> getTreeNode(int h, Object k) {
            return ((parent != null) ? root() : this).find(h, k, null);
        }
        //对name是否相同 返回 -1和1
        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) <= System.identityHashCode(b) ?
                     -1 : 1);
            return d;
        }

        //形成树方法
        final void treeify(Node<K,V>[] tab) {
            TreeNode<K,V> root = null;
            for (TreeNode<K,V> x = this, next; x != null; x = next) {
                next = (TreeNode<K,V>)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,V> p = root;;) {
                        int dir, ph;
                        K pk = p.key;
                        if ((ph = p.hash) > h)
                            dir = -1;
                        else if (ph < h)
                            dir = 1;
                        else if ((kc == null &&
                                  (kc = comparableClassFor(k)) == null) ||
                                 (dir = compareComparables(kc, k, pk)) == 0)
                            dir = tieBreakOrder(k, pk);

                        TreeNode<K,V> xp = p;
                        if ((p = (dir <= 0) ? p.left : p.right) == null) {
                            x.parent = xp;
                            if (dir <= 0)
                                xp.left = x;
                            else
                                xp.right = x;
                            root = balanceInsertion(root, x);
                            break;
                        }
                    }
                }
            }
            moveRootToFront(tab, root);
        }

        //替换树节点方法
        final Node<K,V> untreeify(HashMap<K,V> map) {
            Node<K,V> hd = null, tl = null;
            for (Node<K,V> q = this; q != null; q = q.next) {
                Node<K,V> p = map.replacementNode(q, null);
                if (tl == null)
                    hd = p;
                else
                    tl.next = p;
                tl = p;
            }
            return hd;
        }

        //添加树方法
        final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
                                       int h, K k, V v) {
            Class<?> kc = null;
            boolean searched = false;
            TreeNode<K,V> root = (parent != null) ? root() : this;
            for (TreeNode<K,V> p = root;;) {
                int dir, ph; K pk;
                if ((ph = p.hash) > h)
                    dir = -1;
                else if (ph < h)
                    dir = 1;
                else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                    return p;
                else if ((kc == null &&
                          (kc = comparableClassFor(k)) == null) ||
                         (dir = compareComparables(kc, k, pk)) == 0) {
                    if (!searched) {
                        TreeNode<K,V> 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,V> xp = p;
                if ((p = (dir <= 0) ? p.left : p.right) == null) {
                    Node<K,V> xpn = xp.next;
                    TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
                    if (dir <= 0)
                        xp.left = x;
                    else
                        xp.right = x;
                    xp.next = x;
                    x.parent = x.prev = xp;
                    if (xpn != null)
                        ((TreeNode<K,V>)xpn).prev = x;
                    moveRootToFront(tab, balanceInsertion(root, x));
                    return null;
                }
            }
        }

        //删除树节点
        final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
                                  boolean movable) {
            int n;
            if (tab == null || (n = tab.length) == 0)
                return;
            int index = (n - 1) & hash;
            TreeNode<K,V> first = (TreeNode<K,V>)tab[index], root = first, rl;
            TreeNode<K,V> succ = (TreeNode<K,V>)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
                || (movable
                    && (root.right == null
                        || (rl = root.left) == null
                        || rl.left == null))) {
                tab[index] = first.untreeify(map); // too small
                return;
            }
            TreeNode<K,V> p = this, pl = left, pr = right, replacement;
            if (pl != null && pr != null) {
                TreeNode<K,V> 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,V> sr = s.right;
                TreeNode<K,V> pp = p.parent;
                if (s == pr) { // p was s's direct parent
                    p.parent = s;
                    s.right = p;
                }
                else {
                    TreeNode<K,V> 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,V> 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,V> r = p.red ? root : balanceDeletion(root, replacement);

            if (replacement == p) { // detach
                TreeNode<K,V> 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);
        }

        //map分割方法
        final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
            TreeNode<K,V> b = this;
            // Relink into lo and hi lists, preserving order
            TreeNode<K,V> loHead = null, loTail = null;
            TreeNode<K,V> hiHead = null, hiTail = null;
            int lc = 0, hc = 0;
            for (TreeNode<K,V> e = b, next; e != null; e = next) {
                next = (TreeNode<K,V>)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 <= UNTREEIFY_THRESHOLD)
                    tab[index] = loHead.untreeify(map);
                else {
                    tab[index] = loHead;
                    if (hiHead != null) // (else is already treeified)
                        loHead.treeify(tab);
                }
            }
            if (hiHead != null) {
                if (hc <= UNTREEIFY_THRESHOLD)
                    tab[index + bit] = hiHead.untreeify(map);
                else {
                    tab[index + bit] = hiHead;
                    if (loHead != null)
                        hiHead.treeify(tab);
                }
            }
        }

        //读取红黑树方法
        static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,
                                              TreeNode<K,V> p) {
            TreeNode<K,V> 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,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,
                                               TreeNode<K,V> p) {
            TreeNode<K,V> 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,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,
                                                    TreeNode<K,V> x) {
            x.red = true;
            for (TreeNode<K,V> 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,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,
                                                   TreeNode<K,V> x) {
            for (TreeNode<K,V> 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,V> 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,V> 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;
                        }
                    }
                }
            }
        }

        /**
         * 递归检查
         */
        static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
            TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
                tb = t.prev, tn = (TreeNode<K,V>)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 < t.hash))
                return false;
            if (t.red && tl != null && tl.red && tr != null && tr.red)
                return false;
            if (tl != null && !checkInvariants(tl))
                return false;
            if (tr != null && !checkInvariants(tr))
                return false;
            return true;
        }
    }

}