Java基础-容器

Java集合概述

集合类结构与关系

Map结尾的实现了Map接口,其他的都实现了Collection接口.

Map接口源码

JDK版本1.8.0_261,可以看到除了一些容器的增,删,查,迭代操作以外,还有一些JDK1.8以后提供的默认方法和静态方法,使用到了函数式编程参数传入的是一个Funcation对象。

package java.util;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.io.Serializable;
 *
 * @param <K> the type of keys maintained by this map
 * @param <V> the type of mapped values
 *
 * @author  Josh Bloch
 * @see HashMap
 * @see TreeMap
 * @see Hashtable
 * @see SortedMap
 * @see Collection
 * @see Set
 * @since 1.2
 */
public interface Map<K,V> {
    int size();
    boolean isEmpty();
    boolean containsKey(Object key);
    boolean containsValue(Object value);
    V get(Object key);
    V put(K key, V value);
    V remove(Object key);
    void putAll(Map<? extends K, ? extends V> m);
    void clear();
    Set<K> keySet();
    Collection<V> values();
    Set<Map.Entry<K, V>> entrySet();
    interface Entry<K,V> {
        K getKey();
        V getValue();
        V setValue(V value);
        boolean equals(Object o);
        int hashCode();
        /**
         * @since 1.8
         */
        public static <K extends Comparable<? super K>, V> Comparator<Map.Entry<K,V>> comparingByKey() {
            return (Comparator<Map.Entry<K, V>> & Serializable)
                (c1, c2) -> c1.getKey().compareTo(c2.getKey());
        }
        /**
         * @since 1.8
         */
        public static <K, V extends Comparable<? super V>> Comparator<Map.Entry<K,V>> comparingByValue() {
            return (Comparator<Map.Entry<K, V>> & Serializable)
                (c1, c2) -> c1.getValue().compareTo(c2.getValue());
        }
        /**
         * @since 1.8
         */
        public static <K, V> Comparator<Map.Entry<K, V>> comparingByKey(Comparator<? super K> cmp) {
            Objects.requireNonNull(cmp);
            return (Comparator<Map.Entry<K, V>> & Serializable)
                (c1, c2) -> cmp.compare(c1.getKey(), c2.getKey());
        }
        /**
         * @since 1.8
         */
        public static <K, V> Comparator<Map.Entry<K, V>> comparingByValue(Comparator<? super V> cmp) {
            Objects.requireNonNull(cmp);
            return (Comparator<Map.Entry<K, V>> & Serializable)
                (c1, c2) -> cmp.compare(c1.getValue(), c2.getValue());
        }
    }
    boolean equals(Object o);
    int hashCode();
    // Defaultable methods
    /**
     * @since 1.8
     */
    default V getOrDefault(Object key, V defaultValue) {
        V v;
        return (((v = get(key)) != null) || containsKey(key))
            ? v
            : defaultValue;
    }
    /**
     * @since 1.8
     */
    default void forEach(BiConsumer<? super K, ? super V> action) {
        Objects.requireNonNull(action);
        for (Map.Entry<K, V> entry : entrySet()) {
            K k;
            V v;
            try {
                k = entry.getKey();
                v = entry.getValue();
            } catch(IllegalStateException ise) {
                // this usually means the entry is no longer in the map.
                throw new ConcurrentModificationException(ise);
            }
            action.accept(k, v);
        }
    }
    /**
     * @since 1.8
     */
    default void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
        Objects.requireNonNull(function);
        for (Map.Entry<K, V> entry : entrySet()) {
            K k;
            V v;
            try {
                k = entry.getKey();
                v = entry.getValue();
            } catch(IllegalStateException ise) {
                // this usually means the entry is no longer in the map.
                throw new ConcurrentModificationException(ise);
            }
            // ise thrown from function is not a cme.
            v = function.apply(k, v);
            try {
                entry.setValue(v);
            } catch(IllegalStateException ise) {
                // this usually means the entry is no longer in the map.
                throw new ConcurrentModificationException(ise);
            }
        }
    }
    /**
     * If the specified key is not already associated with a value (or is mapped
     * to {@code null}) associates it with the given value and returns
     * {@code null}, else returns the current value.
     *
     * @since 1.8
     */
    default V putIfAbsent(K key, V value) {
        V v = get(key);
        if (v == null) {
            v = put(key, value);
        }
        return v;
    }
    /**
     * Removes the entry for the specified key only if it is currently
     * mapped to the specified value.
     * @since 1.8
     */
    default boolean remove(Object key, Object value) {
        Object curValue = get(key);
        if (!Objects.equals(curValue, value) ||
            (curValue == null && !containsKey(key))) {
            return false;
        }
        remove(key);
        return true;
    }
    /**
     * Replaces the entry for the specified key only if currently
     * mapped to the specified value.
     *
     * @since 1.8
     */
    default boolean replace(K key, V oldValue, V newValue) {
        Object curValue = get(key);
        if (!Objects.equals(curValue, oldValue) ||
            (curValue == null && !containsKey(key))) {
            return false;
        }
        put(key, newValue);
        return true;
    }
    /**
     * Replaces the entry for the specified key only if it is
     * currently mapped to some value.
     *
     * @since 1.8
     */
    default V replace(K key, V value) {
        V curValue;
        if (((curValue = get(key)) != null) || containsKey(key)) {
            curValue = put(key, value);
        }
        return curValue;
    }
    /**
     * If the specified key is not already associated with a value (or is mapped
     * to {@code null}), attempts to compute its value using the given mapping
     * function and enters it into this map unless {@code null}.
     * @since 1.8
     */
    default V computeIfAbsent(K key,
            Function<? super K, ? extends V> mappingFunction) {
        Objects.requireNonNull(mappingFunction);
        V v;
        if ((v = get(key)) == null) {
            V newValue;
            if ((newValue = mappingFunction.apply(key)) != null) {
                put(key, newValue);
                return newValue;
            }
        }
        return v;
    }
    /**
     * If the value for the specified key is present and non-null, attempts to
     * compute a new mapping given the key and its current mapped value.
     *
     * <p>If the function returns {@code null}, the mapping is removed.  If the
     * function itself throws an (unchecked) exception, the exception is
     * rethrown, and the current mapping is left unchanged.
     * @since 1.8
     */
    default V computeIfPresent(K key,
            BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
        Objects.requireNonNull(remappingFunction);
        V oldValue;
        if ((oldValue = get(key)) != null) {
            V newValue = remappingFunction.apply(key, oldValue);
            if (newValue != null) {
                put(key, newValue);
                return newValue;
            } else {
                remove(key);
                return null;
            }
        } else {
            return null;
        }
    }
    /**
     * Attempts to compute a mapping for the specified key and its current
     * mapped value (or {@code null} if there is no current mapping). For
     * example, to either create or append a {@code String} msg to a value
     * mapping:
     *
     * @since 1.8
     */
    default V compute(K key,
            BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
        Objects.requireNonNull(remappingFunction);
        V oldValue = get(key);
        V newValue = remappingFunction.apply(key, oldValue);
        if (newValue == null) {
            // delete mapping
            if (oldValue != null || containsKey(key)) {
                // something to remove
                remove(key);
                return null;
            } else {
                // nothing to do. Leave things as they were.
                return null;
            }
        } else {
            // add or replace old mapping
            put(key, newValue);
            return newValue;
        }
    }
    /**
     * If the specified key is not already associated with a value or is
     * associated with null, associates it with the given non-null value.
     * Otherwise, replaces the associated value with the results of the given
     * remapping function, or removes if the result is {@code null}. This
     * method may be of use when combining multiple mapped values for a key.
     * For example, to either create or append a {@code String msg} to a
     * value mapping:
     * @since 1.8
     */
    default V merge(K key, V value,
            BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
        Objects.requireNonNull(remappingFunction);
        Objects.requireNonNull(value);
        V oldValue = get(key);
        V newValue = (oldValue == null) ? value :
                   remappingFunction.apply(oldValue, value);
        if(newValue == null) {
            remove(key);
        } else {
            put(key, newValue);
        }
        return newValue;
    }
}

Iterable源码

主要的方法只有一个iterator,但是为了支持Java8的函数式编程Stream也提供了一个默认方法for Each

package java.lang;
import java.util.Iterator;
import java.util.Objects;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;
/**
 * Implementing this interface allows an object to be the target of
 * the "for-each loop" statement.
 *
 * @since 1.5
 * @jls 14.14.2 The enhanced for statement
 */
public interface Iterable<T> {
    /**
     * Returns an iterator over elements of type {@code T}.
     *
     * @return an Iterator.
     */
    Iterator<T> iterator();
    /**
     * Performs the given action for each element of the {@code Iterable}
     * until all elements have been processed or the action throws an
     * exception.  Unless otherwise specified by the implementing class,
     * actions are performed in the order of iteration (if an iteration order
     * is specified).  Exceptions thrown by the action are relayed to the
     * caller
     * @since 1.8
     */
    default void forEach(Consumer<? super T> action) {
        Objects.requireNonNull(action);
        for (T t : this) {
            action.accept(t);
        }
    }
    /**
     * Creates a {@link Spliterator} over the elements described by this
     * {@code Iterable}.
     * @since 1.8
     */
    default Spliterator<T> spliterator() {
        return Spliterators.spliteratorUnknownSize(iterator(), 0);
    }
}

Collection源码

同样,为了支持Stream操作,增加了一些默认方法

package java.util;
import java.util.function.Predicate;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
 * The root interface in the <i>collection hierarchy</i>.  A collection
 * represents a group of objects, known as its <i>elements</i>.  Some
 * collections allow duplicate elements and others do not.  Some are ordered
 * and others unordered.  The JDK does not provide any <i>direct</i>
 * implementations of this interface: it provides implementations of more
 * specific subinterfaces like <tt>Set</tt> and <tt>List</tt>.  This interface
 * is typically used to pass collections around and manipulate them where
 * maximum generality is desired.
 *
 * @author  Josh Bloch
 * @author  Neal Gafter
 * @see     Set
 * @see     List
 * @see     Map
 * @see     SortedSet
 * @see     SortedMap
 * @see     HashSet
 * @see     TreeSet
 * @see     ArrayList
 * @see     LinkedList
 * @see     Vector
 * @see     Collections
 * @see     Arrays
 * @see     AbstractCollection
 * @since 1.2
 */
public interface Collection<E> extends Iterable<E> {
    int size();
    boolean isEmpty();
    boolean contains(Object o);
    Iterator<E> iterator();
    Object[] toArray();
    <T> T[] toArray(T[] a);
    boolean add(E e);
    boolean remove(Object o);
    boolean containsAll(Collection<?> c);
    boolean addAll(Collection<? extends E> c);
    boolean removeAll(Collection<?> c);
    /**
     * Removes all of the elements of this collection that satisfy the given
     * predicate.  Errors or runtime exceptions thrown during iteration or by
     * the predicate are relayed to the caller.
     * @since 1.8
     */
    default boolean removeIf(Predicate<? super E> filter) {
        Objects.requireNonNull(filter);
        boolean removed = false;
        final Iterator<E> each = iterator();
        while (each.hasNext()) {
            if (filter.test(each.next())) {
                each.remove();
                removed = true;
            }
        }
        return removed;
    }
    boolean retainAll(Collection<?> c);
    void clear();
    boolean equals(Object o);
    int hashCode();
    /**
     * Creates a {@link Spliterator} over the elements in this collection.
     * @since 1.8
     */
    @Override
    default Spliterator<E> spliterator() {
        return Spliterators.spliterator(this, 0);
    }
    /**
     * Returns a sequential {@code Stream} with this collection as its source.
     * @since 1.8
     */
    default Stream<E> stream() {
        return StreamSupport.stream(spliterator(), false);
    }
    /**
     * Returns a possibly parallel {@code Stream} with this collection as its
     * source.  It is allowable for this method to return a sequential stream.
     * @since 1.8
     */
    default Stream<E> parallelStream() {
        return StreamSupport.stream(spliterator(), true);
    }
}

HashMap源码解析

简介

HashMap采用key/value存储结构，每个key对应唯一的value，查询和修改的速度都很快，能达到O(1)的平均时间复杂度。它是非线程安全的，且不保证元素存储的顺序；

继承体系

HashMap实现了Cloneable，可以被克隆。
HashMap实现了Serializable，可以被序列化。

HashMap继承自AbstractMap，实现了Map接口，具有Map的所有功能。

存储结构

在Java中，HashMap的实现采用了（数组 + 链表 + 红黑树）的复杂结构，数组的一个元素又称作桶。
在添加元素时，会根据hash值算出元素在数组中的位置，如果该位置没有元素，则直接把元素放置在此处，如果该位置有元素了，则把元素以链表的形式放置在链表的尾部。
当一个链表的元素个数达到一定的数量（且数组的长度达到一定的长度）后，则把链表转化为红黑树，从而提高效率。
数组的查询效率为O(1)，链表的查询效率是O(k)，红黑树的查询效率是O(log k)，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。

源码解析

属性

/**
 * 默认的初始容量为16
 */
static final int DEFAULT_INITIAL_CAPACITY = 1 << 4;
/**
 * 最大的容量为2的30次方
 */
static final int MAXIMUM_CAPACITY = 1 << 30;
/**
 * 默认的装载因子
 */
static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
 * 当一个桶中的元素个数大于等于8时进行树化
 */
static final int TREEIFY_THRESHOLD = 8;
/**
 * 当一个桶中的元素个数小于等于6时把树转化为链表
 */
static final int UNTREEIFY_THRESHOLD = 6;
/**
 * 当桶的个数达到64的时候才进行树化
 */
static final int MIN_TREEIFY_CAPACITY = 64;
/**
 * 数组，又叫作桶（bucket）
 */
transient Node<K,V>[] table;
/**
 * 作为entrySet()的缓存
 */
transient Set<Map.Entry<K,V>> entrySet;
/**
 * 元素的数量
 */
transient int size;
/**
 * 修改次数，用于在迭代的时候执行快速失败策略
 */
transient int modCount;
/**
 * 当桶的使用数量达到多少时进行扩容，threshold = capacity * loadFactor
 */
int threshold;
/**
 * 装载因子
 */
final float loadFactor;
复制代码

（1）容量
容量为数组的长度，亦即桶的个数，默认为16，最大为2的30次方，当容量达到64时才可以树化。
（2）装载因子
装载因子用来计算容量达到多少时才进行扩容，默认装载因子为0.75。
（3）树化
树化，当容量达到64且链表的长度达到8时进行树化，当链表的长度小于6时反树化。

Node内部类-链表基类

Node是一个典型的单链表节点，其中，hash用来存储key计算得来的hash值。

 /**
     * 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; //Key计算出来的Hash值
        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;
        }
        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;
        }
    }
复制代码

TreeNode内部类-红黑树基类

这是一个神奇的类，它继承自LinkedHashMap中的Entry类，关于LInkedHashMap.Entry这个类我们后面再讲。
TreeNode是一个典型的树型节点,它实现了一颗红黑树，其中，prev是链表中的节点，用于在删除元素的时候可以快速找到它的前置节点。

/**
     * 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;
        }
        /**
         * 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;
                if (root == null) {
                    x.parent = null;
                    x.red = false;
                    root = x;
                }
                else {
                    K k = x.key;
                    int h = x.hash;
                    Class<?> kc = null;
                    for (TreeNode<K,V> p = root;;) {
                        int dir, ph;
                        K pk = p.key;
                        if ((ph = p.hash) > h)
                            dir = -1;
                        else if (ph < h)
                            dir = 1;
                        else if ((kc == null &&
                                  (kc = comparableClassFor(k)) == null) ||
                                 (dir = compareComparables(kc, k, pk)) == 0)
                            dir = tieBreakOrder(k, pk);
                        TreeNode<K,V> xp = p;
                        if ((p = (dir <= 0) ? p.left : p.right) == null) {
                            x.parent = xp;
                            if (dir <= 0)
                                xp.left = x;
                            else
                                xp.right = x;
                            root = balanceInsertion(root, x);
                            break;
                        }
                    }
                }
            }
            moveRootToFront(tab, root);
        }
        /**
         * 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;
        }
        /**
         * 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;
            boolean searched = false;
            TreeNode<K,V> root = (parent != null) ? root() : this;
            for (TreeNode<K,V> p = root;;) {
                int dir, ph; K pk;
                if ((ph = p.hash) > h)
                    dir = -1;
                else if (ph < h)
                    dir = 1;
                else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                    return p;
                else if ((kc == null &&
                          (kc = comparableClassFor(k)) == null) ||
                         (dir = compareComparables(kc, k, pk)) == 0) {
                    if (!searched) {
                        TreeNode<K,V> q, ch;
                        searched = true;
                        if (((ch = p.left) != null &&
                             (q = ch.find(h, k, kc)) != null) ||
                            ((ch = p.right) != null &&
                             (q = ch.find(h, k, kc)) != null))
                            return q;
                    }
                    dir = tieBreakOrder(k, pk);
                }
                TreeNode<K,V> xp = p;
                if ((p = (dir <= 0) ? p.left : p.right) == null) {
                    Node<K,V> xpn = xp.next;
                    TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
                    if (dir <= 0)
                        xp.left = x;
                    else
                        xp.right = x;
                    xp.next = x;
                    x.parent = x.prev = xp;
                    if (xpn != null)
                        ((TreeNode<K,V>)xpn).prev = x;
                    moveRootToFront(tab, balanceInsertion(root, x));
                    return null;
                }
            }
        }
        /**
         * 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;
        }
    }