hashMap源码解读

HashMap

（1）HashMap是一种散列表，采用（数组 + 链表 + 红黑树）的存储结构；

（2）HashMap的默认初始容量为16（1<<4），默认装载因子为0.75f，容量总是2的n次方；

（3）HashMap扩容时每次容量变为原来的两倍；

（4）当桶的数量小于64时不会进行树化，只会扩容；

（5）当桶的数量大于64且单个桶中元素的数量大于8时，进行树化；

（6）当单个桶中元素数量小于6时，进行反树化；

（7）HashMap是非线程安全的容器；

（8）HashMap查找添加元素的时间复杂度都为O(1)；

为什么会用三种数据结构:

数组的查询效率为O(1)->定位是哪个桶（时间复杂度O(1)如果没有冲突那么查询过程完毕），链表的查询效率是O(k)->定位桶内的元素（如果有冲突），红黑树的查询效率是O(log k)->定位桶内的元素（如果有冲突），k为桶中的元素个数(所以当元素数量非常多的时候，转化为红黑树能极大地提高效率)

存储结构

包位置

HashMap位于java.util包

蓝线继承，绿线实现

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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;

依赖关系

HashMap继承了AbstractMap，实现了Map，Cloneable，Serializable接口

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public class HashMap<K,V> extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable {

    private static final long serialVersionUID = 362498820763181265L;

HashMap的默认参数

变量 默认值 功能
DEFAULT_INITIAL_CAPACITY 16 初始桶的数目
MAXIMUM_CAPACITY $2^{30}$ 最大容量
DEFAULT_LOAD_FACTOR 0.75 负载因子
TREEIFY_THRESHOLD 8 将链表转化成红黑树的阈值
MIN_TREEIFY_CAPACITY 64 桶树化的阈值（当桶的个数达到64的时候才进行树化）

Hash表每次会扩容长度为以前的2倍

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/**
 * The default initial capacity - MUST be a power of two.
 */
static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

/**
 * The maximum capacity, used if a higher value is implicitly specified
 * by either of the constructors with arguments.
 * MUST be a power of two <= 1<<30.
 */
static final int MAXIMUM_CAPACITY = 1 << 30;

/**
 * The load factor used when none specified in constructor.
 */
static final float DEFAULT_LOAD_FACTOR = 0.75f;

/**
 * The bin count threshold for using a tree rather than list for a
 * bin.  Bins are converted to trees when adding an element to a
 * bin with at least this many nodes. The value must be greater
 * than 2 and should be at least 8 to mesh with assumptions in
 * tree removal about conversion back to plain bins upon
 * shrinkage.
 */
static final int TREEIFY_THRESHOLD = 8;

/**
 * The bin count threshold for untreeifying a (split) bin during a
 * resize operation. Should be less than TREEIFY_THRESHOLD, and at
 * most 6 to mesh with shrinkage detection under removal.
 */
static final int UNTREEIFY_THRESHOLD = 6;

/**
 * The smallest table capacity for which bins may be treeified.
 * (Otherwise the table is resized if too many nodes in a bin.)
 * Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
 * between resizing and treeification thresholds.
 */
static final int MIN_TREEIFY_CAPACITY = 64;

桶元素的数据结构（数组的每个元素的数据结构）

每个节点包含四个属性，hash，键，值，和下一个元素的指针

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/**
 * Basic hash bin node, used for most entries.  (See below for
 * TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
 */
static class Node<K,V> implements Map.Entry<K,V> {
    final int hash;
    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; }

    public final int hashCode() {
        return Objects.hashCode(key) ^ Objects.hashCode(value);
    }

    public final V setValue(V newValue) {
        V oldValue = value;
        value = newValue;
        return oldValue;
    }
    // 判断元素的地址是否相同，相同则equals，否则判断键和值是不是完全相同，相同则equals
    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;
    }
}
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/* ---------------- Static utilities -------------- */

static final int hash(Object key) {
    int h;
    // 如果key为null，则hash值为0，否则调用key的hashCode()方法
    // 并让高16位与整个hash异或，这样做是为了使计算出的hash更分散
    return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}

/**
 * Returns x's Class if it is of the form "class C implements
 * Comparable<C>", else null.
 */
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;
}

/**
 * Returns k.compareTo(x) if x matches kc (k's screened comparable
 * class), else 0.
 */
@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));
}

/**
 * Returns a power of two size for the given target capacity.
 */
// 处理容量使其成为2的幂
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;
}

成员变量

变量 术语 说明
size 大小 HashMap的存储大小
threshold 临界值 HashMap大小达到临界值，需要重新分配大小。
loadFactor 负载因子 HashMap大小负载因子，默认为75%。
modCount 统一修改 HashMap被修改或者删除的次数总数。
Entry 实体 HashMap存储对象的实际实体，由Key，value，hash，next组成。 
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/* ---------------- Fields -------------- */
transient Node<K,V>[] table;// 桶数组 length is always a power of two

/**
 * Holds cached entrySet(). Note that AbstractMap fields are used
 * for keySet() and values().
 */
transient Set<Map.Entry<K,V>> entrySet;
transient int size;
transient int modCount;
int threshold;
final float loadFactor;

构造函数

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

/**
 * Constructs an empty <tt>HashMap</tt> with the specified initial
 * capacity and load factor.
 *
 * @param  initialCapacity the initial capacity
 * @param  loadFactor      the load factor
 * @throws IllegalArgumentException if the initial capacity is negative
 *         or the load factor is nonpositive
 */
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;
    this.threshold = tableSizeFor(initialCapacity);
}

/**
 * Constructs an empty <tt>HashMap</tt> with the specified initial
 * capacity and the default load factor (0.75).
 *
 * @param  initialCapacity the initial capacity.
 * @throws IllegalArgumentException if the initial capacity is negative.
 */
public HashMap(int initialCapacity) {
    this(initialCapacity, DEFAULT_LOAD_FACTOR);
}

/**
 * Constructs an empty <tt>HashMap</tt> with the default initial capacity
 * (16) and the default load factor (0.75).
 */
public HashMap() {
    this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
}

/**
 * Constructs a new <tt>HashMap</tt> with the same mappings as the
 * specified <tt>Map</tt>.  The <tt>HashMap</tt> is created with
 * default load factor (0.75) and an initial capacity sufficient to
 * hold the mappings in the specified <tt>Map</tt>.
 *
 * @param   m the map whose mappings are to be placed in this map
 * @throws  NullPointerException if the specified map is null
 */
public HashMap(Map<? extends K, ? extends V> m) {
    this.loadFactor = DEFAULT_LOAD_FACTOR;
    putMapEntries(m, false);
}

常用方法

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public int size() {
    return size;
}

public boolean isEmpty() {
    return size == 0;
}

public boolean containsKey(Object key) {
    return getNode(hash(key), key) != null;
}

public V get(Object key) {
    Node<K,V> e;
    return (e = getNode(hash(key), key)) == null ? null : e.value;
}

get()方法的实现

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/**
 * Implements Map.get and related methods.
 *
 * @param hash hash for key
 * @param key the key
 * @return the node, or null if none
 */
final Node<K,V> getNode(int hash, Object key) {
    Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
    // 检查边界条件
    if ((tab = table) != null && (n = tab.length) > 0 &&
        (first = tab[(n - 1) & hash]) != null) {
        // 总是检查第一个Node是不是要找的
        if (first.hash == hash && // always check first node
            ((k = first.key) == key || (key != null && key.equals(k))))
            return first;
        // 如果第一个不是要找的
        if ((e = first.next) != null) {
            // 看下一个节点是不是TreeNode
            if (first instanceof TreeNode)
                // 是TreeNode使用树查找
                return ((TreeNode<K,V>)first).getTreeNode(hash, key);
            do {
                // 不是TreeNode 进行链表查找
                if (e.hash == hash &&
                    ((k = e.key) == key || (key != null && key.equals(k))))
                    return e;
            } while ((e = e.next) != null);
        }
    }
    return null;
}

put方法的实现

（1）计算key的hash值；

（2）如果桶（数组）数量为0，则初始化桶；

（3）如果key所在的桶没有元素，则直接插入；

（4）如果key所在的桶中的第一个元素的key与待插入的key相同，说明找到了元素，转后续流程（9）处理；

（5）如果第一个元素是树节点，则调用树节点的putTreeVal()寻找元素或插入树节点；

（6）如果不是以上三种情况，则遍历桶对应的链表查找key是否存在于链表中；

（7）如果找到了对应key的元素，则转后续流程（9）处理；

（8）如果没找到对应key的元素，则在链表最后插入一个新节点并判断是否需要树化；

（9）如果找到了对应key的元素，则判断是否需要替换旧值，并直接返回旧值；

（10）如果插入了元素，则数量加1并判断是否需要扩容；

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

/**
 * Implements Map.put and related methods.
 *
 * @param hash hash for key
 * @param key the key
 * @param value the value to put
 * @param onlyIfAbsent if true, don't change existing value
 * @param evict if false, the table is in creation mode.
 * @return previous value, or null if none
 */
final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
               boolean evict) {
    Node<K,V>[] tab; Node<K,V> p; int n, i;
    // 如果没有初始化,初始化，分配内存
    if ((tab = table) == null || (n = tab.length) == 0)
        n = (tab = resize()).length;
    // 如果要放的位置 (n - 1) & hash 没有元素，直接分配内并放元素
    if ((p = tab[i = (n - 1) & hash]) == null)
        tab[i] = newNode(hash, key, value, null);
    else {
        Node<K,V> e; K k;
        // 如果桶中第一个元素的key与待插入元素的key相同，保存到e中用于后续修改value值
        if (p.hash == hash &&
            ((k = p.key) == key || (key != null && key.equals(k))))
            e = p;
        else if (p instanceof TreeNode)
            // 如果第一个元素是树节点，则调用树节点的putTreeVal插入元素
            e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
        else {
            // 遍历这个桶对应的链表，binCount用于存储链表中元素的个数
            for (int binCount = 0; ; ++binCount) {
                // 如果链表遍历完了都没有找到相同key的元素，说明该key对应的元素不存在，则在链表最后插入一个新节点
                if ((e = p.next) == null) {
                    p.next = newNode(hash, key, value, null);
                    // 如果插入新节点后链表长度大于8，则判断是否需要树化，因为第一个元素没有加到binCount中，所以这里-1
                    if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
                        treeifyBin(tab, hash);
                    break;
                }
                // 如果插入新节点后链表长度大于8，则判断是否需要树化，因为第一个元素没有加到binCount中，所以这里-1
                if (e.hash == hash &&
                    ((k = e.key) == key || (key != null && key.equals(k))))
                    break;
                p = e;
            }
        }

        // 如果找到了对应key的元素
        if (e != null) { // existing mapping for key
            V oldValue = e.value;
            if (!onlyIfAbsent || oldValue == null)
                e.value = value;
            afterNodeAccess(e);
            return oldValue;
        }
    }
    ++modCount;
    // 判断是否需要扩容
    if (++size > threshold)
        resize();
    afterNodeInsertion(evict);
    return null;
}

resize()方法的实现

（1）如果使用是默认构造方法，则第一次插入元素时初始化为默认值，容量为16，扩容门槛为12；

（2）如果使用的是非默认构造方法，则第一次插入元素时初始化容量等于扩容门槛，扩容门槛在构造方法里等于传入容量向上最近的2的n次方；

（3）如果旧容量大于0，则新容量等于旧容量的2倍，但不超过最大容量2的30次方，新扩容门槛为旧扩容门槛的2倍；

（4）创建一个新容量的桶；

（5）搬移元素，原链表分化成两个链表(原红黑树分成两棵树)，低位链表存储在原来桶的位置，高位链表搬移到原来桶的位置加旧容量的位置；

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/**
 * Initializes or doubles table size.  If null, allocates in
 * accord with initial capacity target held in field threshold.
 * Otherwise, because we are using power-of-two expansion, the
 * elements from each bin must either stay at same index, or move
 * with a power of two offset in the new table.
 *
 * @return the table
 */
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) {
        if (oldCap >= MAXIMUM_CAPACITY) {
            // 如果旧容量达到了最大容量，则不再进行扩容
            threshold = Integer.MAX_VALUE;
            return oldTab;
        }
        else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                 oldCap >= DEFAULT_INITIAL_CAPACITY)
            // 如果旧容量的两倍小于最大容量，并且旧容量大于默认初始容量（16），则容量扩大为两倍，扩容阈值也扩大为两倍
            newThr = oldThr << 1; // double threshold
    }
    else if (oldThr > 0) // initial capacity was placed in threshold
        // 使用非默认构造方法创建的map，第一次插入元素会走到这里
        // 如果旧容量为0且旧扩容阈值大于0，则把新容量赋值为旧阈值
        newCap = oldThr;
    else {               // zero initial threshold signifies using defaults
        // 调用默认构造方法创建的map，第一次插入元素会走到这里
        // 如果旧容量旧扩容阈值都是0，说明还未初始化过，则初始化容量为默认容量，扩容阈值为默认容量*默认装载因子
        newCap = DEFAULT_INITIAL_CAPACITY;
        newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
    }
    if (newThr == 0) {
        // 如果新的阈值是0，则阈值应为新的容量乘以负载因子的值
        float ft = (float)newCap * loadFactor;
        newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
                  (int)ft : Integer.MAX_VALUE);
    }
    // 修改扩容后的阈值
    threshold = newThr;
    // 创建新的Node数组（桶数组）
    @SuppressWarnings({"rawtypes","unchecked"})
    Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
    table = newTab;
    if (oldTab != null) {
        for (int j = 0; j < oldCap; ++j) {
            Node<K,V> e;
            // 如果桶中第一个元素不为空，赋值给e
            if ((e = oldTab[j]) != null) {
                // 清空旧桶，便于GC回收  
                oldTab[j] = null;
                // 如果后面不跟着其余的元素
                if (e.next == null)
                    // 如果这个桶中只有一个元素，则计算它在新桶中的位置并把它搬移到新桶中
                    // 因为每次都扩容两倍，所以这里的第一个元素搬移到新桶的时候新桶肯定还没有元素
                    newTab[e.hash & (newCap - 1)] = e;
                else if (e instanceof TreeNode)
                    // 如果后面跟着红黑树，则把这颗树打散成两颗树插入到新桶中去
                    ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
                else { // preserve order
                    // 如果这个链表不止一个元素且不是一颗树
                    // 则分化成两个链表插入到新的桶中去
                    // 比如，假如原来容量为4，3、7、11、15这四个元素都在三号桶中
                    // 现在扩容到8，则3和11还是在三号桶，7和15要搬移到七号桶中去
                    // 也就是分化成了两个链表
                    Node<K,V> loHead = null, loTail = null;
                    Node<K,V> hiHead = null, hiTail = null;
                    Node<K,V> next;
                    do {
                        next = e.next;
                        // (e.hash & oldCap) == 0的元素放在低位链表中
                        // 比如，3 & 4 == 0
                        if ((e.hash & oldCap) == 0) {
                            if (loTail == null)
                                loHead = e;
                            else
                                loTail.next = e;
                            loTail = e;
                        }
                        else {
                            // (e.hash & oldCap) != 0的元素放在高位链表中
                            // 比如，7 & 4 != 0
                            if (hiTail == null)
                                hiHead = e;
                            else
                                hiTail.next = e;
                            hiTail = e;
                        }
                    } while ((e = next) != null);
                    // 遍历完成分化成两个链表了
                    // 低位链表在新桶中的位置与旧桶一样（即3和11还在三号桶中）
                    if (loTail != null) {
                        loTail.next = null;
                        newTab[j] = loHead;
                    }
                    // 高位链表在新桶中的位置正好是原来的位置加上旧容量（即7和15搬移到七号桶了）
                    if (hiTail != null) {
                        hiTail.next = null;
                        newTab[j + oldCap] = hiHead;
                    }
                }
            }
        }
    }
    return newTab;
}

treeifyBin()与方法实现

（1）从链表的第一个元素开始遍历；

（2）将第一个元素作为根节点；

（3）其它元素依次插入到红黑树中，再做平衡；

（4）将根节点移到链表第一元素的位置（因为平衡的时候根节点会改变）；

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/**
 * Replaces all linked nodes in bin at index for given hash unless
 * table is too small, in which case resizes instead.
 */
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)
        // 如果桶数量小于64，直接扩容而不用树化
        // 因为扩容之后，链表会分化成两个链表，达到减少元素的作用
        // 当然也不一定，比如容量为4，里面存的全是除以4余数等于3的元素
        // 这样即使扩容也无法减少链表的长度
        resize();
    else if ((e = tab[index = (n - 1) & hash]) != null) {
        TreeNode<K,V> hd = null, tl = null;// 头节点和尾节点
        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);
        // 如果进入过上面的循环，则从头节点开始树化
        if ((tab[index] = hd) != null)
            hd.treeify(tab);
    }
}


putAll的实现

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/**
 * Copies all of the mappings from the specified map to this map.
 * These mappings will replace any mappings that this map had for
 * any of the keys currently in the specified map.
 *
 * @param m mappings to be stored in this map
 * @throws NullPointerException if the specified map is null
 */
public void putAll(Map<? extends K, ? extends V> m) {
    putMapEntries(m, true);
}
/**
 * Implements Map.putAll and Map constructor.
 *
 * @param m the map
 * @param evict false when initially constructing this map, else
 * true (relayed to method afterNodeInsertion).
 */
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);
        }
    }
}

remove()的实现

（1）先查找元素所在的节点；

（2）如果找到的节点是树节点，则按树的移除节点处理；

（3）如果找到的节点是桶中的第一个节点，则把第二个节点移到第一的位置；

（4）否则按链表删除节点处理；

（5）修改size，调用移除节点后置处理等；

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

/**
 * Implements Map.remove and related methods.
 *
 * @param hash hash for key
 * @param key the key
 * @param value the value to match if matchValue, else ignored
 * @param matchValue if true only remove if value is equal
 * @param movable if false do not move other nodes while removing
 * @return the node, or null if none
 */
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;
    if ((tab = table) != null && (n = tab.length) > 0 &&
        (p = tab[index = (n - 1) & hash]) != null) {
        // 要删除的元素存在
        Node<K,V> node = null, e; K k; V v;
        if (p.hash == hash &&
            ((k = p.key) == key || (key != null && key.equals(k))))
            // 第一个元素是要删除的元素
            node = p;
        else if ((e = p.next) != null) {
            // 第一个不是要删除的元素，如果第二个是红黑树节点，红黑树查找要删除的节点
            if (p instanceof TreeNode)
                node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
            else {
                // 第一个不是要删除的元素，如果第二个是链表的节点，链表定位到要删除的节点
                do {
                    if (e.hash == hash &&
                        ((k = e.key) == key ||
                         (key != null && key.equals(k)))) {
                        node = e;
                        break;
                    }
                    p = e;
                } while ((e = e.next) != null);
            }
        }
        // 如果找到了元素，则看参数是否需要匹配value值，如果不需要匹配直接删除，如果需要匹配则看value值是否与传入的value相等
        if (node != null && (!matchValue || (v = node.value) == value ||
                             (value != null && value.equals(v)))) {
            if (node instanceof TreeNode)
                // 如果是树节点，调用树的删除方法（以node调用的，是删除自己）
                ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
            else if (node == p)
                // 如果待删除的元素是第一个元素，则把第二个元素移到第一的位置
                tab[index] = node.next;
            else
                // 否则删除node节点
                p.next = node.next;
            ++modCount;
            --size;
            // 删除节点后置处理
            afterNodeRemoval(node);
            return node;
        }
    }
    return null;
}

/**
 * Removes all of the mappings from this map.
 * The map will be empty after this call returns.
 */
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;
    }
}

/**
 * Returns <tt>true</tt> if this map maps one or more keys to the
 * specified value.
 *
 * @param value value whose presence in this map is to be tested
 * @return <tt>true</tt> if this map maps one or more keys to the
 *         specified value
 */
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;
}

/**
 * Returns a {@link Set} view of the keys contained in this map.
 * The set is backed by the map, so changes to the map are
 * reflected in the set, and vice-versa.  If the map is modified
 * while an iteration over the set is in progress (except through
 * the iterator's own <tt>remove</tt> operation), the results of
 * the iteration are undefined.  The set supports element removal,
 * which removes the corresponding mapping from the map, via the
 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
 * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
 * operations.  It does not support the <tt>add</tt> or <tt>addAll</tt>
 * operations.
 *
 * @return a set view of the keys contained in this map
 */
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();
        }
    }
}

/**
 * Returns a {@link Collection} view of the values contained in this map.
 * The collection is backed by the map, so changes to the map are
 * reflected in the collection, and vice-versa.  If the map is
 * modified while an iteration over the collection is in progress
 * (except through the iterator's own <tt>remove</tt> operation),
 * the results of the iteration are undefined.  The collection
 * supports element removal, which removes the corresponding
 * mapping from the map, via the <tt>Iterator.remove</tt>,
 * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
 * <tt>retainAll</tt> and <tt>clear</tt> operations.  It does not
 * support the <tt>add</tt> or <tt>addAll</tt> operations.
 *
 * @return a view of the values contained in this map
 */
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();
        }
    }
}

/**
 * Returns a {@link Set} view of the mappings contained in this map.
 * The set is backed by the map, so changes to the map are
 * reflected in the set, and vice-versa.  If the map is modified
 * while an iteration over the set is in progress (except through
 * the iterator's own <tt>remove</tt> operation, or through the
 * <tt>setValue</tt> operation on a map entry returned by the
 * iterator) the results of the iteration are undefined.  The set
 * supports element removal, which removes the corresponding
 * mapping from the map, via the <tt>Iterator.remove</tt>,
 * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
 * <tt>clear</tt> operations.  It does not support the
 * <tt>add</tt> or <tt>addAll</tt> operations.
 *
 * @return a set view of the mappings contained in this map
 */
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();
        }
    }
}

// Overrides of JDK8 Map extension methods

@Override
public V getOrDefault(Object key, V defaultValue) {
    Node<K,V> e;
    return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
}

@Override
public V putIfAbsent(K key, V value) {
    return putVal(hash(key), key, value, true, true);
}

@Override
public boolean remove(Object key, Object value) {
    return removeNode(hash(key), key, value, true, true) != null;
}

@Override
public boolean replace(K key, V oldValue, V newValue) {
    Node<K,V> e; V v;
    if ((e = getNode(hash(key), key)) != null &&
        ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
        e.value = newValue;
        afterNodeAccess(e);
        return true;
    }
    return false;
}

@Override
public V replace(K key, V value) {
    Node<K,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) {
    if (mappingFunction == 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;
        if (old != null && (oldValue = old.value) != null) {
            afterNodeAccess(old);
            return oldValue;
        }
    }
    V v = mappingFunction.apply(key);
    if (v == null) {
        return null;
    } else if (old != null) {
        old.value = v;
        afterNodeAccess(old);
        return v;
    }
    else if (t != null)
        t.putTreeVal(this, tab, hash, key, v);
    else {
        tab[i] = newNode(hash, key, v, first);
        if (binCount >= TREEIFY_THRESHOLD - 1)
            treeifyBin(tab, hash);
    }
    ++modCount;
    ++size;
    afterNodeInsertion(true);
    return v;
}

public V computeIfPresent(K key,
                          BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
    if (remappingFunction == null)
        throw new NullPointerException();
    Node<K,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;
}

@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;
}

@Override
public V merge(K key, V value,
               BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
    if (value == null)
        throw new NullPointerException();
    if (remappingFunction == null)
        throw new NullPointerException();
    int hash = hash(key);
    Node<K,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);
        }
    }
    if (old != null) {
        V v;
        if (old.value != null)
            v = remappingFunction.apply(old.value, value);
        else
            v = value;
        if (v != null) {
            old.value = v;
            afterNodeAccess(old);
        }
        else
            removeNode(hash, key, null, false, true);
        return v;
    }
    if (value != null) {
        if (t != null)
            t.putTreeVal(this, tab, hash, key, value);
        else {
            tab[i] = newNode(hash, key, value, first);
            if (binCount >= TREEIFY_THRESHOLD - 1)
                treeifyBin(tab, hash);
        }
        ++modCount;
        ++size;
        afterNodeInsertion(true);
    }
    return value;
}

@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
    Node<K,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();
    }
}

@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
    Node<K,V>[] tab;
    if (function == 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) {
                e.value = function.apply(e.key, e.value);
            }
        }
        if (modCount != mc)
            throw new ConcurrentModificationException();
    }
}

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

/**
 * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
 * values themselves are not cloned.
 *
 * @return a shallow copy of this map
 */
@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;
}

// These methods are also used when serializing HashSets
final float loadFactor() { return loadFactor; }
final int capacity() {
    return (table != null) ? table.length :
        (threshold > 0) ? threshold :
        DEFAULT_INITIAL_CAPACITY;
}

/**
 * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
 * serialize it).
 *
 * @serialData The <i>capacity</i> of the HashMap (the length of the
 *             bucket array) is emitted (int), followed by the
 *             <i>size</i> (an int, the number of key-value
 *             mappings), followed by the key (Object) and value (Object)
 *             for each key-value mapping.  The key-value mappings are
 *             emitted in no particular order.
 */
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);
}

/**
 * Reconstitutes this map from a stream (that is, deserializes it).
 * @param s the stream
 * @throws ClassNotFoundException if the class of a serialized object
 *         could not be found
 * @throws IOException if an I/O error occurs
 */
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);
        }
    }
}

/* ------------------------------------------------------------ */
// iterators

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(); }
}

/* ------------------------------------------------------------ */
// spliterators

static class HashMapSpliterator<K,V> {
    final HashMap<K,V> map;
    Node<K,V> current;          // current node
    int index;                  // current index, modified on advance/split
    int fence;                  // one past last index
    int est;                    // size estimate
    int expectedModCount;       // for comodification checks

    HashMapSpliterator(HashMap<K,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;
    }

    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;
    }

    public final long estimateSize() {
        getFence(); // force init
        return (long) est;
    }
}

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);
    }

    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();
        }
    }

    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;
    }

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

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);
    }
}

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;
    }
}

/* ------------------------------------------------------------ */
// LinkedHashMap support


/*
 * The following package-protected methods are designed to be
 * overridden by LinkedHashMap, but not by any other subclass.
 * Nearly all other internal methods are also package-protected
 * but are declared final, so can be used by LinkedHashMap, view
 * classes, and HashSet.
 */

// Create a regular (non-tree) node
Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
    return new Node<>(hash, key, value, next);
}

// For conversion from TreeNodes to plain nodes
Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
    return new Node<>(p.hash, p.key, p.value, next);
}

// Create a tree bin node
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);
}

/**
 * Reset to initial default state.  Called by clone and readObject.
 */
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) { }

// Called only from writeObject, to ensure compatible ordering.
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

/**
 * Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn
 * extends Node) so can be used as extension of either regular or
 * linked node.
 */
static final class TreeNode<K,V> extends LinkedHashMap.Entry<K,V> {
    TreeNode<K,V> parent;  // red-black tree links
    TreeNode<K,V> left;
    TreeNode<K,V> right;
    TreeNode<K,V> prev;    // needed to unlink next upon deletion
    boolean red;
    TreeNode(int hash, K key, V val, Node<K,V> next) {
        super(hash, key, val, next);
    }

    /**
     * Returns root of tree containing this node.
     */
    final TreeNode<K,V> root() {
        for (TreeNode<K,V> r = this, p;;) {
            if ((p = r.parent) == null)
                return r;
            r = p;
        }
    }

    /**
     * Ensures that the given root is the first node of its bin.
     */
    static <K,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);
        }
    }

    /**
     * Finds the node starting at root p with the given hash and key.
     * The kc argument caches comparableClassFor(key) upon first use
     * comparing keys.
     */
    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;
    }

    /**
     * Calls find for root node.
     */
    final TreeNode<K,V> getTreeNode(int h, Object k) {
        return ((parent != null) ? root() : this).find(h, k, null);
    }

    /**
     * Tie-breaking utility for ordering insertions when equal
     * hashCodes and non-comparable. We don't require a total
     * order, just a consistent insertion rule to maintain
     * equivalence across rebalancings. Tie-breaking further than
     * necessary simplifies testing a bit.
     */
    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;
    }

TreeNode的treeify（）方法

（1）从链表的第一个元素开始遍历；

（2）将第一个元素作为根节点；

（3）其它元素依次插入到红黑树中，再做平衡；

（4）将根节点移到链表第一元素的位置（因为平衡的时候根节点会改变）；

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/**
 * Forms tree of the nodes linked from this node.
 */
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;
        // 第一个元素作为根节点且为黑节点，其它元素依次插入到树中再做平衡
        if (root == null) {
            x.parent = null;
            x.red = false;
            root = x;
        }
        else {
            K k = x.key;
            int h = x.hash;
            Class<?> kc = null;
            // 从根节点查找元素插入的位置
            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);
                // 如果最后没找到元素，则插入
                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;
                    // 插入后平衡，默认插入的是红节点，在balanceInsertion()方法里
                    root = balanceInsertion(root, x);
                    break;
                }
            }
        }
    }
    // 把根节点移动到链表的头节点，因为经过平衡之后原来的第一个元素不一定是根节点了
    moveRootToFront(tab, root);
}

/**
 * Returns a list of non-TreeNodes replacing those linked from
 * this node.
 */
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;
}

向红黑树中插入元素putTreeVal（）

（1）寻找根节点；

（2）从根节点开始查找；

（3）比较hash值及key值，如果都相同，直接返回，在putVal()方法中决定是否要替换value值；

（4）根据hash值及key值确定在树的左子树还是右子树查找，找到了直接返回；

（5）如果最后没有找到则在树的相应位置插入元素，并做平衡；

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/**
 * Tree version of putVal.
 */
final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
                               int h, K k, V v) {
    Class<?> kc = null;
    // 标记是否找到这个key的节点
    boolean searched = false;
    // 定位到根节点
    TreeNode<K,V> root = (parent != null) ? root() : this;
    for (TreeNode<K,V> p = root;;) {
        // dir=direction，标记是在左边还是右边
        // ph=p.hash，当前节点的hash值
        // pk=p.key，当前节点的key值
        int dir, ph; K pk;
        if ((ph = p.hash) > h)
            // 当前hash比目标hash大，说明在左边
            dir = -1;
        else if (ph < h)
            // 当前hash比目标hash小，说明在右边
            dir = 1;
        else if ((pk = p.key) == k || (k != null && k.equals(pk)))
            // 两者hash相同且key相等，说明找到了节点，直接返回该节点
            // 回到putVal()中判断是否需要修改其value值
            return p;
        else if ((kc == null &&
                // 如果k是Comparable的子类则返回其真实的类，否则返回null
                  (kc = comparableClassFor(k)) == null) ||
                  // 如果k和pk不是同样的类型则返回0，否则返回两者比较的结果
                 (dir = compareComparables(kc, k, pk)) == 0) {
                    // 这个条件表示两者hash相同但是其中一个不是Comparable类型或者两者类型不同
                    // 比如key是Object类型，这时可以传String也可以传Integer，两者hash值可能相同
                    // 在红黑树中把同样hash值的元素存储在同一颗子树，这里相当于找到了这颗子树的顶点
                    // 从这个顶点分别遍历其左右子树去寻找有没有跟待插入的key相同的元素

            if (!searched) {
                TreeNode<K,V> q, ch;
                searched = true;
                 // 遍历左右子树找到了直接返回
                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;
            }
            // 如果两者类型相同，再根据它们的内存地址计算hash值进行比较
            dir = tieBreakOrder(k, pk);
        }

        TreeNode<K,V> xp = p;
        if ((p = (dir <= 0) ? p.left : p.right) == null) {
            // 如果最后确实没找到对应key的元素，则新建一个节点
            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;
            // 插入树节点后平衡
            // 把root节点移动到链表的第一个节点
            moveRootToFront(tab, balanceInsertion(root, x));
            return null;
        }
    }
}

红黑树删除元素removeTreeNode（）

（1）TreeNode本身既是链表节点也是红黑树节点；

（2）先删除链表节点；

（3）再删除红黑树节点并做平衡；

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        /**
         * Removes the given node, that must be present before this call.
         * This is messier than typical red-black deletion code because we
         * cannot swap the contents of an interior node with a leaf
         * successor that is pinned by "next" pointers that are accessible
         * independently during traversal. So instead we swap the tree
         * linkages. If the current tree appears to have too few nodes,
         * the bin is converted back to a plain bin. (The test triggers
         * somewhere between 2 and 6 nodes, depending on tree structure).
         */
        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);
        }

        /**
         * Splits nodes in a tree bin into lower and upper tree bins,
         * or untreeifies if now too small. Called only from resize;
         * see above discussion about split bits and indices.
         *
         * @param map the map
         * @param tab the table for recording bin heads
         * @param index the index of the table being split
         * @param bit the bit of hash to split on
         */
        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);
                }
            }
        }

        /* ------------------------------------------------------------ */
        // Red-black tree methods, all adapted from CLR

        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;
                        }
                    }
                }
            }
        }

        /**
         * Recursive invariant check
         */
        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;
        }
    }

}

参考文献

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作者：技术见闻
链接：https://www.jianshu.com/p/8b372f3a195d
来源：简书
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
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作者：彤哥读源码
链接：https://juejin.cn/post/6844903817855631373
来源：掘金
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
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    缺失模块。
    1、请确保node版本大于6.2
    2、在博客根目录（注意不是yilia根目录）执行以下命令：
    npm i hexo-generator-json-content --save

    3、在根目录_config.yml里添加配置： 

      jsonContent:
    meta: false
    pages: false
    posts:
      title: true
      date: true
      path: true
      text: false
      raw: false
      content: false
      slug: false
      updated: false
      comments: false
      link: false
      permalink: false
      excerpt: false
      categories: false
      tags: true

我是一只<br>又水又笨又菜的<br>菜狗子<br>希望有一天被领走