HashMap源码解析

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;


public class HashMap extends AbstractMap
        implements Map, Cloneable, Serializable {

    //默认初始容量为16 位运算更高效
    static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16
    //最大容量为2的30次幂 位运算更高效
    static final int MAXIMUM_CAPACITY = 1 << 30;
    //默认负载因子，当插入元素时，超过（当前容量*负载因子）（如未初始化容量为默认容量）此时就该扩容了，加载因子越大时间利用越多，越小利用的空间越多，权衡后为0.75（概率论）。
    static final float DEFAULT_LOAD_FACTOR = 0.75f;
    ///链表变树的阈值，java8之前解决hash冲突是通过链表的方式，java8中引入了红黑树，当某个hash节点冲突大于【TREEIFY_THRESHOLD】，使用红黑树，从而大大的提高查找效率（平衡树查询性能更好，但是增删操作性能低于红黑树）
    static final int TREEIFY_THRESHOLD = 8;
    //取消树阀值，在红黑树中节点数量小于6个，将其转化为链表结构
    static final int UNTREEIFY_THRESHOLD = 6;
    //最小的树化容量，链表树化红黑树条件：
    //1，链表中元素数量超过(>)8个;
    //2, 满足map中元素个数(size)大于等于64否则会先扩容，扩容对解决hash冲突更有效。
    static final int MIN_TREEIFY_CAPACITY = 64;
    private static final long serialVersionUID = 362498820763181265L;
    
    final float loadFactor;

    
    
    transient Node[] table;
    
    transient Set> entrySet;
    
    transient int size;
    
    transient int modCount;

    
    
    // (The javadoc description is true upon serialization.
    // Additionally, if the table array has not been allocated, this
    // field holds the initial array capacity, or zero signifying
    // DEFAULT_INITIAL_CAPACITY.)
    int threshold;

    
    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);
    }

    
    public HashMap(int initialCapacity) {
        this(initialCapacity, DEFAULT_LOAD_FACTOR);
    }

    
    public HashMap() {
        this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
    }

    
    public HashMap(Map m) {
        this.loadFactor = DEFAULT_LOAD_FACTOR;
        putMapEntries(m, false);
    }

    //key的hash计算方式
    static final int hash(Object key) {
        int h;
        return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16); //这段代码叫“扰动函数”，详见https://www.zhihu.com/question/20733617
    }

    

    //如果对象x的类是C，如果C实现了Comparable接口，那么返回C，否则返回null
    static Class comparableClassFor(Object x) {
        if (x instanceof Comparable) {   //判断x是否是实现Comparable接口的对象
            Class c;
            Type[] ts, as;
            Type t;
            ParameterizedType p;
            if ((c = x.getClass()) == String.class) // bypass checks //如果x是个字符串，则返回String.class ,因为String类是实现Comparable接口的对象
                return c;
            if ((ts = c.getGenericInterfaces()) != null) {  // 如果 c 不是字符串类，获取c直接实现的接口（如果是泛型接口则附带泛型信息）    
                for (int i = 0; i < ts.length; ++i) {   // 遍历接口数组
                    if (((t = ts[i]) instanceof ParameterizedType) &&    //如果当前接口t是个泛型接口
                            ((p = (ParameterizedType) t).getRawType() ==    //如果该泛型接口t的原始类型p 是 Comparable 接口
                                    Comparable.class) &&
                            (as = p.getActualTypeArguments()) != null &&  // 如果该Comparable接口p只定义了一个泛型参数
                            as.length == 1 && as[0] == c) // type arg is c 
                        return c;   // 如果这一个泛型参数的类型就是c，那么返回c
                }

                // 上面for循环的目的就是为了看看x的class是否 implements  Comparable
            }
        }
        return null;  // 如果c并没有实现 Comparable 那么返回空
    }

    //如果x所属的类是kc，返回k.compareTo(x)的比较结果，如果x为空，或者其所属的类不是kc，返回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));
    }

    //通过位运算进行扩容（无符号右移）2 倍扩容
    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;
    }

    
    final void putMapEntries(Map 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 e : m.entrySet()) {
                K key = e.getKey();
                V value = e.getValue();
                putVal(hash(key), key, value, false, evict);
            }
        }
    }

    
    //返回个数
    public int size() {
        return size;
    }

    // 是否为空
    public boolean isEmpty() {
        return size == 0;
    }

    //调用内部方法通过key查找value
    public V get(Object key) {
        Node e;
        return (e = getNode(hash(key), key)) == null ? null : e.value;
    }

    final Node getNode(int hash, Object key) {
        Node[] tab;
        Node first, e;
        int n;
        K k;
        // 桶不为空，那么进行查找，否则直接返回 null。
        if ((tab = table) != null && (n = tab.length) > 0 &&
                //HashMap 中的桶数组大小总是为 2 的幂。在这个情况下，(n - 1) & hash 等价于对 length 取余，算一个小优化
                (first = tab[(n - 1) & hash]) != null) {
            //检查要查找的是否是第一个节点，是则返回第一个节点
            if (first.hash == hash && // always check first node
                    ((k = first.key) == key || (key != null && key.equals(k))))
                return first;
            //沿着第一个节点继续查找
            if ((e = first.next) != null) {
                //如果是红黑树，调用红黑树的查找方法
                if (first instanceof TreeNode)
                    return ((TreeNode) first).getTreeNode(hash, key);
                //如果是链表，调用链表查找方法
                do {
                    if (e.hash == hash &&
                            ((k = e.key) == key || (key != null && key.equals(k))))
                        return e;
                } while ((e = e.next) != null);
            }
        }
        return null;
    }

    //判断Map中是否包含Key
    public boolean containsKey(Object key) {
        return getNode(hash(key), key) != null;
    }

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

    

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

    final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
                   boolean evict) {
        Node[] tab;
        Node p;
        int n, i;
        if ((tab = table) == null || (n = tab.length) == 0)
            n = (tab = resize()).length;
        if ((p = tab[i = (n - 1) & hash]) == null)
            tab[i] = newNode(hash, key, value, null);
        else {
            Node e;
            K k;
            if (p.hash == hash &&
                    ((k = p.key) == key || (key != null && key.equals(k))))
                e = p;
            else if (p instanceof TreeNode)
                e = ((TreeNode) p).putTreeval(this, tab, hash, key, value);
            else {
                for (int binCount = 0; ; ++binCount) {
                    if ((e = p.next) == null) {
                        p.next = newNode(hash, key, value, null);
                        if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
                            treeifyBin(tab, hash);
                        break;
                    }
                    if (e.hash == hash &&
                            ((k = e.key) == key || (key != null && key.equals(k))))
                        break;
                    p = e;
                }
            }
            if (e != null) { // existing mapping for key
                V oldValue = e.value;
                if (!onlyIfAbsent || oldValue == null)
                    e.value = value;
                afterNodeAccess(e);
                return oldValue;
            }
        }
        ++modCount;
        if (++size > threshold)
            resize();
        afterNodeInsertion(evict);
        return null;
    }

    
    final Node[] resize() {
        Node[] oldTab = table;    //保存扩容前表的数据
        int oldCap = (oldTab == null) ? 0 : oldTab.length;  //
        int oldThr = threshold;
        int newCap, newThr = 0;
        if (oldCap > 0) {
            if (oldCap >= MAXIMUM_CAPACITY) {
                threshold = Integer.MAX_VALUE;
                return oldTab;
            } else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                    oldCap >= DEFAULT_INITIAL_CAPACITY)
                newThr = oldThr << 1; // double threshold
        } else if (oldThr > 0) // initial capacity was placed in threshold
            newCap = oldThr;
        else {               // zero initial threshold signifies using defaults
            newCap = DEFAULT_INITIAL_CAPACITY;
            newThr = (int) (DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
        }
        if (newThr == 0) {
            float ft = (float) newCap * loadFactor;
            newThr = (newCap < MAXIMUM_CAPACITY && ft < (float) MAXIMUM_CAPACITY ?
                    (int) ft : Integer.MAX_VALUE);
        }
        threshold = newThr;
        @SuppressWarnings({"rawtypes", "unchecked"})
        Node[] newTab = (Node[]) new Node[newCap];
        table = newTab;
        if (oldTab != null) {
            for (int j = 0; j < oldCap; ++j) {
                Node 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) e).split(this, newTab, j, oldCap);
                    else { // preserve order
                        Node loHead = null, loTail = null;
                        Node hiHead = null, hiTail = null;
                        Node next;
                        do {
                            next = e.next;
                            if ((e.hash & oldCap) == 0) {
                                if (loTail == null)
                                    loHead = e;
                                else
                                    loTail.next = e;
                                loTail = e;
                            } else {
                                if (hiTail == null)
                                    hiHead = e;
                                else
                                    hiTail.next = e;
                                hiTail = e;
                            }
                        } while ((e = next) != null);
                        if (loTail != null) {
                            loTail.next = null;
                            newTab[j] = loHead;
                        }
                        if (hiTail != null) {
                            hiTail.next = null;
                            newTab[j + oldCap] = hiHead;
                        }
                    }
                }
            }
        }
        return newTab;
    }

    
    final void treeifyBin(Node[] tab, int hash) {
        int n, index;
        Node e;
        if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
            resize();
        else if ((e = tab[index = (n - 1) & hash]) != null) {
            TreeNode hd = null, tl = null;
            do {
                TreeNode p = replacementTreeNode(e, null);
                if (tl == null)
                    hd = p;
                else {
                    p.prev = tl;
                    tl.next = p;
                }
                tl = p;
            } while ((e = e.next) != null);
            if ((tab[index] = hd) != null)
                hd.treeify(tab);
        }
    }

    
    public void putAll(Map m) {
        putMapEntries(m, true);
    }

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

    
    final Node removeNode(int hash, Object key, Object value,
                                boolean matchValue, boolean movable) {
        Node[] tab;
        Node p;
        int n, index;
        if ((tab = table) != null && (n = tab.length) > 0 &&
                (p = tab[index = (n - 1) & hash]) != null) {
            Node node = null, e;
            K k;
            V v;
            if (p.hash == hash &&
                    ((k = p.key) == key || (key != null && key.equals(k))))
                node = p;
            else if ((e = p.next) != null) {
                if (p instanceof TreeNode)
                    node = ((TreeNode) p).getTreeNode(hash, key);
                else {
                    do {
                        if (e.hash == hash &&
                                ((k = e.key) == key ||
                                        (key != null && key.equals(k)))) {
                            node = e;
                            break;
                        }
                        p = e;
                    } while ((e = e.next) != null);
                }
            }
            if (node != null && (!matchValue || (v = node.value) == value ||
                    (value != null && value.equals(v)))) {
                if (node instanceof TreeNode)
                    ((TreeNode) node).removeTreeNode(this, tab, movable);
                else if (node == p)
                    tab[index] = node.next;
                else
                    p.next = node.next;
                ++modCount;
                --size;
                afterNodeRemoval(node);
                return node;
            }
        }
        return null;
    }

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

    
    public boolean containsValue(Object value) {
        Node[] tab;
        V v;
        if ((tab = table) != null && size > 0) {
            for (int i = 0; i < tab.length; ++i) {
                for (Node e = tab[i]; e != null; e = e.next) {
                    if ((v = e.value) == value ||
                            (value != null && value.equals(v)))
                        return true;
                }
            }
        }
        return false;
    }

    
    public Set keySet() {
        Set ks = keySet;
        if (ks == null) {
            ks = new KeySet();
            keySet = ks;
        }
        return ks;
    }

    
    public Collection values() {
        Collection vs = values;
        if (vs == null) {
            vs = new Values();
            values = vs;
        }
        return vs;
    }

    
    public Set> entrySet() {
        Set> es;
        return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
    }

    @Override
    public V getOrDefault(Object key, V defaultValue) {
        Node 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 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;
    }

    // Overrides of JDK8 Map extension methods

    @Override
    public V replace(K key, V value) {
        Node 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 mappingFunction) {
        if (mappingFunction == null)
            throw new NullPointerException();
        int hash = hash(key);
        Node[] tab;
        Node first;
        int n, i;
        int binCount = 0;
        TreeNode t = null;
        Node 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) first).getTreeNode(hash, key);
            else {
                Node 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 remappingFunction) {
        if (remappingFunction == null)
            throw new NullPointerException();
        Node 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 remappingFunction) {
        if (remappingFunction == null)
            throw new NullPointerException();
        int hash = hash(key);
        Node[] tab;
        Node first;
        int n, i;
        int binCount = 0;
        TreeNode t = null;
        Node 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) first).getTreeNode(hash, key);
            else {
                Node 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 remappingFunction) {
        if (value == null)
            throw new NullPointerException();
        if (remappingFunction == null)
            throw new NullPointerException();
        int hash = hash(key);
        Node[] tab;
        Node first;
        int n, i;
        int binCount = 0;
        TreeNode t = null;
        Node 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) first).getTreeNode(hash, key);
            else {
                Node 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 action) {
        Node[] 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 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 function) {
        Node[] 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 e = tab[i]; e != null; e = e.next) {
                    e.value = function.apply(e.key, e.value);
                }
            }
            if (modCount != mc)
                throw new ConcurrentModificationException();
        }
    }

    
    @SuppressWarnings("unchecked")
    @Override
    public Object clone() {
        HashMap result;
        try {
            result = (HashMap) 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;
    }

    
    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);
    }

    
    // Cloning and serialization

    
    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[] tab = (Node[]) 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);
            }
        }
    }

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

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

    // Create a tree bin node
    TreeNode newTreeNode(int hash, K key, V value, Node next) {
        return new TreeNode<>(hash, key, value, next);
    }

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

    
    // iterators

    
    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 p) {
    }

    void afterNodeInsertion(boolean evict) {
    }

    void afterNodeRemoval(Node p) {
    }

    
    // spliterators

    // Called only from writeObject, to ensure compatible ordering.
    void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
        Node[] tab;
        if (size > 0 && (tab = table) != null) {
            for (int i = 0; i < tab.length; ++i) {
                for (Node e = tab[i]; e != null; e = e.next) {
                    s.writeObject(e.key);
                    s.writeObject(e.value);
                }
            }
        }
    }

    
    //HashMap 的 拉链的节点
    static class Node implements Map.Entry {
        final int hash;  //当前节点的Hash值
        final K key; //当前节点的Key
        V value; //当前节点的Value
        Node next; //指向下一个节点

        //初始化该节点
        Node(int hash, K key, V value, Node next) {
            this.hash = hash;
            this.key = key;
            this.value = value;
            this.next = next;
        }

        //获取该节点的Key
        public final K getKey() {
            return key;
        }

        //获取该节点的Value
        public final V getValue() {
            return value;
        }

        //toString
        public final String toString() {
            return key + "=" + value;
        }

        //进行hash操作 调用Object中的native方法
        public final int hashCode() {
            return Objects.hashCode(key) ^ Objects.hashCode(value);
        }

        //设置值并返回旧值
        public final V setValue(V newValue) {
            V oldValue = value;
            value = newValue;
            return oldValue;
        }

        //equals方法 先比较 地址值 如不相等再比较
        public final boolean equals(Object o) {
            if (o == this)
                return true;
            if (o instanceof Map.Entry) {  //instanceof比较左边的对象是否为右边的实例
                Map.Entry e = (Map.Entry) o;
                return Objects.equals(key, e.getKey()) &&
                        Objects.equals(value, e.getValue());
            }
            return false;
        }
    }

    static class HashMapSpliterator {
        final HashMap map;
        Node 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 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 m = map;
                est = m.size;
                expectedModCount = m.modCount;
                Node[] tab = m.table;
                hi = fence = (tab == null) ? 0 : tab.length;
            }
            return hi;
        }

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

    static final class KeySpliterator
            extends HashMapSpliterator
            implements Spliterator {
        KeySpliterator(HashMap m, int origin, int fence, int est,
                       int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public KeySpliterator 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 action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap m = map;
            Node[] 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 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 action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node[] 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;
        }
    }

    
    // linkedHashMap support


    

    static final class ValueSpliterator
            extends HashMapSpliterator
            implements Spliterator {
        ValueSpliterator(HashMap m, int origin, int fence, int est,
                         int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public ValueSpliterator 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 action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap m = map;
            Node[] 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 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 action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node[] 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
            extends HashMapSpliterator
            implements Spliterator> {
        EntrySpliterator(HashMap m, int origin, int fence, int est,
                         int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public EntrySpliterator 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> action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap m = map;
            Node[] 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 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> action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node[] 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 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;
        }
    }

    
    static final class TreeNode extends linkedHashMap.Entry {
        TreeNode parent;  // red-black tree links
        TreeNode left;
        TreeNode right;
        TreeNode prev;    // needed to unlink next upon deletion
        boolean red;

        TreeNode(int hash, K key, V val, Node next) {
            super(hash, key, val, next);
        }

        
        static  void moveRootToFront(Node[] tab, TreeNode root) {
            int n;
            if (root != null && tab != null && (n = tab.length) > 0) {
                int index = (n - 1) & root.hash;
                TreeNode first = (TreeNode) tab[index];
                if (root != first) {
                    Node rn;
                    tab[index] = root;
                    TreeNode rp = root.prev;
                    if ((rn = root.next) != null)
                        ((TreeNode) rn).prev = rp;
                    if (rp != null)
                        rp.next = rn;
                    if (first != null)
                        first.prev = root;
                    root.next = first;
                    root.prev = null;
                }
                assert checkInvariants(root);
            }
        }

        
        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;
        }

        static  TreeNode rotateLeft(TreeNode root,
                                                TreeNode p) {
            TreeNode 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  TreeNode rotateRight(TreeNode root,
                                                 TreeNode p) {
            TreeNode 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  TreeNode balanceInsertion(TreeNode root,
                                                      TreeNode x) {
            x.red = true;
            for (TreeNode 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  TreeNode balanceDeletion(TreeNode root,
                                                     TreeNode x) {
            for (TreeNode 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 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) && 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 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) && xp.red;
                                if ((sl = xpl.left) != null)
                                    sl.red = false;
                            }
                            if (xp != null) {
                                xp.red = false;
                                root = rotateRight(root, xp);
                            }
                            x = root;
                        }
                    }
                }
            }
        }

        
        static  boolean checkInvariants(TreeNode t) {
            TreeNode tp = t.parent, tl = t.left, tr = t.right,
                    tb = t.prev, tn = (TreeNode) 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;
            return tr == null || checkInvariants(tr);
        }

        
        final TreeNode root() {
            for (TreeNode r = this, p; ; ) {
                if ((p = r.parent) == null)
                    return r;
                r = p;
            }
        }

        
        final TreeNode find(int h, Object k, Class kc) {
            TreeNode p = this;
            do {
                int ph, dir;
                K pk;
                TreeNode 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;
        }

        
        final TreeNode getTreeNode(int h, Object k) {
            return ((parent != null) ? root() : this).find(h, k, null);
        }

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

        
        final void treeify(Node[] tab) {
            TreeNode root = null;
            for (TreeNode x = this, next; x != null; x = next) {
                next = (TreeNode) 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 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 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);
        }

        
        final Node untreeify(HashMap map) {
            Node hd = null, tl = null;
            for (Node q = this; q != null; q = q.next) {
                Node p = map.replacementNode(q, null);
                if (tl == null)
                    hd = p;
                else
                    tl.next = p;
                tl = p;
            }
            return hd;
        }

        
        final TreeNode putTreeval(HashMap map, Node[] tab,
                                        int h, K k, V v) {
            Class kc = null;
            boolean searched = false;
            TreeNode root = (parent != null) ? root() : this;
            for (TreeNode 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 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 xp = p;
                if ((p = (dir <= 0) ? p.left : p.right) == null) {
                    Node xpn = xp.next;
                    TreeNode 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) xpn).prev = x;
                    moveRootToFront(tab, balanceInsertion(root, x));
                    return null;
                }
            }
        }

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

            if (replacement == p) {  // detach
                TreeNode pp = p.parent;
                p.parent = null;
                if (pp != null) {
                    if (p == pp.left)
                        pp.left = null;
                    else if (p == pp.right)
                        pp.right = null;
                }
            }
            if (movable)
                moveRootToFront(tab, r);
        }

        
        final void split(HashMap map, Node[] tab, int index, int bit) {
            TreeNode b = this;
            // Relink into lo and hi lists, preserving order
            TreeNode loHead = null, loTail = null;
            TreeNode hiHead = null, hiTail = null;
            int lc = 0, hc = 0;
            for (TreeNode e = b, next; e != null; e = next) {
                next = (TreeNode) 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);
                }
            }
        }
    }

    final class KeySet extends AbstractSet {
        public final int size() {
            return size;
        }

        public final void clear() {
            HashMap.this.clear();
        }

        public final Iterator 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 spliterator() {
            return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
        }

        public final void forEach(Consumer action) {
            Node[] 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 e = tab[i]; e != null; e = e.next)
                        action.accept(e.key);
                }
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
    }

    final class Values extends AbstractCollection {
        public final int size() {
            return size;
        }

        public final void clear() {
            HashMap.this.clear();
        }

        public final Iterator iterator() {
            return new ValueIterator();
        }

        public final boolean contains(Object o) {
            return containsValue(o);
        }

        public final Spliterator spliterator() {
            return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
        }

        public final void forEach(Consumer action) {
            Node[] 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 e = tab[i]; e != null; e = e.next)
                        action.accept(e.value);
                }
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
    }

    final class EntrySet extends AbstractSet> {
        public final int size() {
            return size;
        }

        public final void clear() {
            HashMap.this.clear();
        }

        public final Iterator> 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 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> spliterator() {
            return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
        }

        public final void forEach(Consumer> action) {
            Node[] 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 e = tab[i]; e != null; e = e.next)
                        action.accept(e);
                }
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
    }

    abstract class HashIterator {
        Node next;        // next entry to return
        Node current;     // current entry
        int expectedModCount;  // for fast-fail
        int index;             // current slot

        HashIterator() {
            expectedModCount = modCount;
            Node[] 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 nextNode() {
            Node[] t;
            Node 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 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 {
        public final K next() {
            return nextNode().key;
        }
    }

    final class ValueIterator extends HashIterator
            implements Iterator {
        public final V next() {
            return nextNode().value;
        }
    }

    
    // Tree bins

    final class EntryIterator extends HashIterator
            implements Iterator> {
        public final Map.Entry next() {
            return nextNode();
        }
    }

}