• 【JDK8】HashMap集合 源码阅读


        JDK8的HashMap数据结构上复杂了很多,因此读取效率得以大大提升,关于源码中红黑树的增删改查,博主没有细读,会在下一篇博文中使用Java实现红黑树的增删改查。

        下面是类的结构图:

         代码(摘抄自JDK):

    import java.lang.reflect.ParameterizedType;
    import java.lang.reflect.Type;
    import java.util.*;
    
    
    
    /**
     * hashMap
     * 作为Kit ,保证健壮、高效,然后才是可阅读性
     * http://www.mamicode.com/info-detail-2219646.html
     * java红黑树:
     * http://www.cnblogs.com/skywang12345/p/3624343.html
     * hashMap中概念解读
     * https://blog.csdn.net/fan2012huan/article/details/51087722
     * hashmap解读:
     * https://blog.csdn.net/AJ1101/article/details/79413939#commentBox
     * <p>
     * 概念摘抄:
     * 约定前面的数组结构的每一个格格称为桶
     * 约定桶后面存放的每一个数据称为bin
     * bin这个术语来自于JDK 1.8的HashMap注释。
     *
     * @param <K>
     * @param <V>
     * @author jdk
     */
    public class HappyMap<K, V> extends HashMap<K, V>
            implements Map<K, V> {
        /**
         * The default initial capacity - MUST be a power of two.
         */
        static final int DEFAULT_INITIAL_CAPACITY = 1 << 4;
        /**
         * The maximum capacity, used if a higher value is implicitly specified
         * by either of the constructors with arguments.
         * MUST be a power of two <= 1<<30.
         * 最大容量,如果一个更高的值被构造函数用参数隐式指定,那么依旧使用这个容量
         * <p>
         * 必须是2的次方
         */
        static final int MAXIMUM_CAPACITY = 1 << 30;
        /**
         * 当没有在构造函数里面指定,将使用这个默认负载因子
         * The load factor used when none specified in constructor
         */
        static final float DEFAULT_LOAD_FACTOR = 0.75f;
        /**
         * The bin count threshold for using a tree rather than list for a
         * bin.  Bins are converted to trees when adding an element to a
         * bin with at least this many nodes. The value must be greater
         * than 2 and should be at least 8 to mesh with assumptions in
         * tree removal about conversion back to plain bins upon
         * shrinkage.
         * 一个bucket的树化阈值(红黑树)
         * <p>
         * 为bin使用tree还是list一个bin数目阈值。在至少达到这个数目节点的情况下增加元素,bins将会转化成tree。该值必须大于2,至少应该是8,与移除树的假设相适应。
         */
        static final int TREEIFY_THRESHOLD = 8;
        /**
         * The bin count threshold for untreeifying a (split) bin during a
         * resize operation. Should be less than TREEIFY_THRESHOLD, and at
         * most 6 to mesh with shrinkage detection under removal.
         * 一个树的链表还原阈值
         * <p>
         * 在调整大小操作时反树化(切分)一个bin的bin数目阈值,在移除时检测最大是6。
         */
        static final int UNTREEIFY_THRESHOLD = 6;
        /**
         * The smallest table capacity for which bins may be treeified.
         * (Otherwise the table is resized if too many nodes in a bin.)
         * Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
         * between resizing and treeification thresholds.
         * 树形化时bins的最小哈希表容量(否则如果bin中有太多的节点就对哈希表调整大小)。
         * 为避免在调整大小和树形化阈值之间产生矛盾,这个值至少是4 * TREEIFY_THERSHOLD。
         */
        static final int MIN_TREEIFY_CAPACITY = 64;
    
        /**
         * NODE-use HashMap
         * Basic hash bin node, used for most entries.  (See below for
         * TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
         */
        static class Node<K, V> implements Map.Entry<K, V> {
            final int hash;
            final K key;
            V value;
            HappyMap.Node<K, V> next;
    
            Node(int hash, K key, V value, HappyMap.Node<K, V> next) {
                this.hash = hash;
                this.key = key;
                this.value = value;
                this.next = next;
            }
    
            @Override
            public final K getKey() {
                return key;
            }
    
            @Override
            public final V getValue() {
                return value;
            }
    
            @Override
            public final String toString() {
                return key + "=" + value;
            }
    
            @Override
            public final int hashCode() {
                return Objects.hashCode(key) ^ Objects.hashCode(value);
            }
    
            @Override
            public final V setValue(V newValue) {
                V oldValue = value;
                value = newValue;
                return oldValue;
            }
    
            @Override
            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;
            }
        }
    
        /**
         * Create a tree bin node
         */
        HappyMap.TreeNode<K, V> newTreeNode(int hash, K key, V value, HappyMap.Node<K, V> next) {
            return new HappyMap.TreeNode<>(hash, key, value, next);
        }
        /* ---------------- Static utilities(没抄) -------------- */
    
        /* ---------------- Fields -------------- */
    
        /**
         * The table, initialized on first use, and resized as
         * necessary. When allocated, length is always a power of two.
         * (We also tolerate length zero in some operations to allow
         * bootstrapping mechanics that are currently not needed.)
         */
        transient HappyMap.Node<K, V>[] table;
    
        /**
         * Holds cached entrySet(). Note that AbstractMap fields are used
         * for keySet() and values().
         */
        transient Set<Map.Entry<K, V>> entrySet;
    
        /**
         * The number of key-value mappings contained in this map.
         */
        transient int size;
    
        /**
         * The number of times this HashMap has been structurally modified
         * Structural modifications are those that change the number of mappings in
         * the HashMap or otherwise modify its internal structure (e.g.,
         * rehash).  This field is used to make iterators on Collection-views of
         * the HashMap fail-fast.  (See ConcurrentModificationException).
         */
        transient int modCount;
    
        /**
         * The next size value at which to resize (capacity * load factor).
         * threshold表示当HashMap的size大于threshold时会执行resize操作。
         * threshold=capacity*loadFactor
         *
         * @serial
         */
        // (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;
    
        /**
         * The load factor for the hash table.
         *
         * @serial
         */
        final float loadFactor;
    
        /**
         * Constructs an empty <tt>HashMap</tt> with the default initial capacity
         * (16) and the default load factor (0.75).
         */
        public HappyMap() {
            // all other fields defaulted
            this.loadFactor = DEFAULT_LOAD_FACTOR;
        }
    
        /* ---------------- Public operations -------------- */
    
    
        @Override
        public Set<Entry<K, V>> entrySet() {
            return null;
        }
    
        /**
         * Returns the number of key-value mappings in this map.
         *
         * @return the number of key-value mappings in this map
         */
        @Override
        public int size() {
            return size;
        }
    
        /**
         * Returns <tt>true</tt> if this map contains no key-value mappings.
         *
         * @return <tt>true</tt> if this map contains no key-value mappings
         */
        @Override
        public boolean isEmpty() {
            return size == 0;
        }
    
    
        /**
         * Computes key.hashCode() and spreads (XORs) higher bits of hash
         * to lower.  Because the table uses power-of-two masking, sets of
         * hashes that vary only in bits above the current mask will
         * always collide. (Among known examples are sets of Float keys
         * holding consecutive whole numbers in small tables.)  So we
         * apply a transform that spreads the impact of higher bits
         * downward. There is a tradeoff between speed, utility, and
         * quality of bit-spreading. Because many common sets of hashes
         * are already reasonably distributed (so don't benefit from
         * spreading), and because we use trees to handle large sets of
         * collisions in bins, we just XOR some shifted bits in the
         * cheapest possible way to reduce systematic lossage, as well as
         * to incorporate impact of the highest bits that would otherwise
         * never be used in index calculations because of table bounds.
         */
        static final int hash(Object key) {
            int h;
            return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
        }
    
        /**
         * Associates the specified value with the specified key in this map.
         * If the map previously contained a mapping for the key, the old
         * value is replaced.
         *
         * @param key   key with which the specified value is to be associated
         * @param value value to be associated with the specified key
         * @return the previous value associated with <tt>key</tt>, or
         * <tt>null</tt> if there was no mapping for <tt>key</tt>.
         * (A <tt>null</tt> return can also indicate that the map
         * previously associated <tt>null</tt> with <tt>key</tt>.)
         */
        @Override
        public V put(K key, V value) {
            return putVal(hash(key), key, value, false, true);
        }
    
        /**
         * Implements Map.put and related methods
         *
         * @param hash         hash for key
         * @param key          the key
         * @param value        the value to put
         * @param onlyIfAbsent if true, don't change existing value
         * @param evict        if false, the table is in creation mode.
         * @return previous value, or null if none
         */
    
        final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
                       boolean evict) {
            HappyMap.Node<K, V>[] tab;
            HappyMap.Node<K, V> calPosiNode;
            int tabLenth, position;
            //如果 table属性 为空,初始化定义大小,返回新的长度(初始化长度)
            if ((tab = table) == null || (tabLenth = tab.length) == 0) {
                tabLenth = (tab = resize()).length;
            }
            //hash(key)&(n-1)查找位置,如果位置上的Node为null,新建一个Node
            if ((calPosiNode = tab[position = (tabLenth - 1) & hash]) == null) {
                tab[position] = newNode(hash, key, value, null);
            } else {//如果位置上有Node了
                HappyMap.Node<K, V> tempNode;
                K k;
                //新旧元素key值相等(或哈希值相同,地址相等),覆盖
                if (calPosiNode.hash == hash && ((k = calPosiNode.key) == key || (key != null && key.equals(k)))) {
                    tempNode = calPosiNode;
                    //如果key不相等且是此位置上的RB树节点
                } else if (calPosiNode instanceof HappyMap.TreeNode) {
                    tempNode = ((HappyMap.TreeNode<K, V>) calPosiNode).putTreeVal(this, tab, hash, key, value);
    
                } else {//key 不相等 且非RB树节点
                    for (int binCount = 0; ; ++binCount) {
                        // 当链表只有一个头部结点,则新建(append)一个结点
                        if ((tempNode = calPosiNode.next) == null) {
                            calPosiNode.next = newNode(hash, key, value, null);
                            // 链表长度大于8(0 to 7)时,将链表转红黑树
                            if (binCount >= TREEIFY_THRESHOLD - 1) {
                                treeifyBin(tab, hash);
                            }
                            break;
                        }
                        if (tempNode.hash == hash && ((k = tempNode.key) == key || (key != null && key.equals(k)))) {
                            break;
                        }
                        //更新
                        calPosiNode = tempNode;
                    }
                }
                // existing mapping for key
                if (tempNode != null) {
                    V oldValue = tempNode.value;
                    if (!onlyIfAbsent || oldValue == null) {
                        tempNode.value = value;
                    }
                    afterNodeAccess(tempNode);
                    return oldValue;
                }
            }
            ++modCount;
            if (++size > threshold) {
                resize();
            }
    
            afterNodeInsertion(evict);
            return null;
        }
    
        // Callbacks to allow LinkedHashMap post-actions
        void afterNodeAccess(HappyMap.Node<K, V> p) {
        }
    
        void afterNodeInsertion(boolean evict) {
        }
    
        /**
         * Initializes or doubles table size.  If null, allocates in
         * accord with initial capacity target held in field threshold.
         * Otherwise, because we are using power-of-two expansion, the
         * elements from each bin must either stay at same index, or move
         * with a power of two offset in the new table.
         * 初始化或者扩容之后元素调整
         *
         * @return the table
         */
        final HappyMap.Node<K, V>[] resize() {
            HappyMap.Node<K, V>[] oldTab = table;
            //原数组长度
            int oldCap = (oldTab == null) ? 0 : oldTab.length;
            //原扩充临界值
            int oldThr = threshold;
            int newCap, newThr = 0;
            //table不为空
            if (oldCap > 0) {
                //如果数组长度达到最大值,则修改临界值为Integer.MAX_VALUE
                if (oldCap >= MAXIMUM_CAPACITY) {
                    threshold = Integer.MAX_VALUE;
                    return oldTab;
                }
                //没有达到最大值则容量*2
                else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                        oldCap >= DEFAULT_INITIAL_CAPACITY) {
                    // doubles threshold
                    newThr = oldThr << 1;
                }
            }
            // initial capacity was placed in threshold(直接赋值)
            else if (oldThr > 0) {
                newCap = oldThr;
            }
            // zero initial threshold signifies using defaults(初始化容量与边界)
            else {
                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"})
            HappyMap.Node<K, V>[] newTab = (HappyMap.Node<K, V>[]) new HappyMap.Node[newCap];
            table = newTab;
            // 调整数组大小之后,需要调整红黑树或者链表的指向
            if (oldTab != null) {
                for (int j = 0; j < oldCap; ++j) {
                    HappyMap.Node<K, V> e;
                    if ((e = oldTab[j]) != null) {
                        oldTab[j] = null;
                        if (e.next == null) {
                            newTab[e.hash & (newCap - 1)] = e;
                        }
                        // 红黑树调整
                        else if (e instanceof HappyMap.TreeNode) {
                            ((HappyMap.TreeNode<K, V>) e).split(this, newTab, j, oldCap);
                        }
                        // preserve order链表顺序调整
                        else {
                            HappyMap.Node<K, V> loHead = null, loTail = null;
                            HappyMap.Node<K, V> hiHead = null, hiTail = null;
                            HappyMap.Node<K, V> 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;
        }
    
        // Create a regular (non-tree) node
        HappyMap.Node<K, V> newNode(int hash, K key, V value, HappyMap.Node<K, V> next) {
            return new HappyMap.Node<>(hash, key, value, next);
        }
    
        // For conversion from TreeNodes to plain nodes
        HappyMap.Node<K, V> replacementNode(HappyMap.Node<K, V> p, HappyMap.Node<K, V> next) {
            return new HappyMap.Node<>(p.hash, p.key, p.value, next);
        }
    
        /**
         * Replaces all linked nodes in bin at index for given hash unless
         * table is too small, in which case resizes instead.
         * bin(Node)转换为 TreeNode
         */
        final void treeifyBin(HappyMap.Node<K, V>[] tab, int hash) {
            int n, index;
            HappyMap.Node<K, V> e;
            if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY) {
                resize();
            } else if ((e = tab[index = (n - 1) & hash]) != null) {
                HappyMap.TreeNode<K, V> hd = null, tl = null;
                do {
                    //Node转TreeNode
                    HappyMap.TreeNode<K, V> p = replacementTreeNode(e, null);
                    if (tl == null) {
                        hd = p;
                    } else {
                        p.prev = tl;
                        tl.next = p;
                    }
                    tl = p;
                } while ((e = e.next) != null);
                if ((tab[index] = hd) != null) {
                    //转为红黑树
                    hd.treeify(tab);
                }
    
            }
        }
    
        // For treeifyBin
        HappyMap.TreeNode<K, V> replacementTreeNode(HappyMap.Node<K, V> p, HappyMap.Node<K, V> next) {
            return new HappyMap.TreeNode<>(p.hash, p.key, p.value, next);
        }
        /**
         * HashMap.Node subclass for normal LinkedHashMap entries.
         */
        /* ------------------------------------------------------------ */
    
        /**
         * Returns x's Class if it is of the form "class C implements
         * Comparable<C>", else null.
         */
        static Class<?> comparableClassFor(Object x) {
            if (x instanceof Comparable) {
                Class<?> c;
                Type[] ts, as;
                Type t;
                ParameterizedType p;
                if ((c = x.getClass()) == String.class) // bypass checks
                    return c;
                if ((ts = c.getGenericInterfaces()) != null) {
                    for (int i = 0; i < ts.length; ++i) {
                        if (((t = ts[i]) instanceof ParameterizedType) &&
                                ((p = (ParameterizedType) t).getRawType() ==
                                        Comparable.class) &&
                                (as = p.getActualTypeArguments()) != null &&
                                as.length == 1 && as[0] == c) // type arg is c
                            return c;
                    }
                }
            }
            return null;
        }
    
        /**
         * Returns k.compareTo(x) if x matches kc (k's screened comparable
         * class), else 0.
         */
        @SuppressWarnings({"rawtypes", "unchecked"}) // for cast to Comparable
        static int compareComparables(Class<?> kc, Object k, Object x) {
            return (x == null || x.getClass() != kc ? 0 :
                    ((Comparable) k).compareTo(x));
        }
    
        /**
         * Returns the value to which the specified key is mapped,
         * or {@code null} if this map contains no mapping for the key.
         *
         * <p>More formally, if this map contains a mapping from a key
         * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
         * key.equals(k))}, then this method returns {@code v}; otherwise
         * it returns {@code null}.  (There can be at most one such mapping.)
         *
         * <p>A return value of {@code null} does not <i>necessarily</i>
         * indicate that the map contains no mapping for the key; it's also
         * possible that the map explicitly maps the key to {@code null}.
         * The {@link #containsKey containsKey} operation may be used to
         * distinguish these two cases.
         *
         * @see #put(Object, Object)
         */
        @Override
        public V get(Object key) {
            HappyMap.Node<K, V> e;
            return (e = getNode(hash(key), key)) == null ? null : e.value;
        }
    
        /**
         * Implements Map.get and related methods
         *
         * @param hash hash for key
         * @param key  the key
         * @return the node, or null if none
         */
        final HappyMap.Node<K, V> getNode(int hash, Object key) {
            HappyMap.Node<K, V>[] tab;
            HappyMap.Node<K, V> first, e;
            int n;
            K k;
            if ((tab = table) != null && (n = tab.length) > 0 &&
                    (first = tab[(n - 1) & hash]) != null) {
                if (first.hash == hash && // always check first node
                        ((k = first.key) == key || (key != null && key.equals(k))))
                    return first;
                if ((e = first.next) != null) {
                    if (first instanceof HappyMap.TreeNode)
                        return ((HappyMap.TreeNode<K, V>) first).getTreeNode(hash, key);
                    do {
                        if (e.hash == hash &&
                                ((k = e.key) == key || (key != null && key.equals(k))))
                            return e;
                    } while ((e = e.next) != null);
                }
            }
            return null;
        }
    
        // Tree bins
    
        /**
         * Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn
         * extends Node) so can be used as extension of either regular or
         * linked node.
         */
        static final class TreeNode<K, V> extends HappyMap.Node<K, V> {
            HappyMap.Entry<K, V> before, after;
    //        TreeNode(int hash, K key, V value, HappyMap.Node<K,V> next) {
    //            super(hash, key, value, next);
    //        }
    
            HappyMap.TreeNode<K, V> parent;  // red-black tree links
            HappyMap.TreeNode<K, V> left;
            HappyMap.TreeNode<K, V> right;
            HappyMap.TreeNode<K, V> prev;    // needed to unlink next upon deletion
            boolean red;
    
            TreeNode(int hash, K key, V val, HappyMap.Node<K, V> next) {
                super(hash, key, val, next);
            }
    
            /**
             * Returns root of tree containing this node.
             */
            final HappyMap.TreeNode<K, V> root() {
                for (HappyMap.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(HappyMap.Node<K, V>[] tab, HappyMap.TreeNode<K, V> root) {
                int n;
                if (root != null && tab != null && (n = tab.length) > 0) {
                    int index = (n - 1) & root.hash;
                    HappyMap.TreeNode<K, V> first = (HappyMap.TreeNode<K, V>) tab[index];
                    if (root != first) {
                        HappyMap.Node<K, V> rn;
                        tab[index] = root;
                        HappyMap.TreeNode<K, V> rp = root.prev;
                        if ((rn = root.next) != null)
                            ((HappyMap.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 HappyMap.TreeNode<K, V> find(int h, Object k, Class<?> kc) {
                HappyMap.TreeNode<K, V> p = this;
                do {
                    int ph, dir;
                    K pk;
                    HappyMap.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 HappyMap.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.
             * 将链表中每个值进行红黑树插入操作
             *
             * @return root of tree
             */
            final void treeify(HappyMap.Node<K, V>[] tab) {
                HappyMap.TreeNode<K, V> root = null;
                for (HappyMap.TreeNode<K, V> x = this, next; x != null; x = next) {
                    next = (HappyMap.TreeNode<K, V>) x.next;
                    // 初始化Root
                    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;
                        //TREENODE节点插入
                        for (HappyMap.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);
                            }
                            HappyMap.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 HappyMap.Node<K, V> untreeify(HappyMap<K, V> map) {
                HappyMap.Node<K, V> hd = null, tl = null;
                for (HappyMap.Node<K, V> q = this; q != null; q = q.next) {
                    HappyMap.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.
             * 红黑树节点插入
             */
            final HappyMap.TreeNode<K, V> putTreeVal(HappyMap<K, V> map,
                                                     HappyMap.Node<K, V>[] tab,
                                                     int h,
                                                     K k,
                                                     V v) {
                Class<?> kc = null;
                boolean searched = false;
                HappyMap.TreeNode<K, V> root = (parent != null) ? root() : this;
                for (HappyMap.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) {
                            HappyMap.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);
                    }
    
                    HappyMap.TreeNode<K, V> xp = p;
                    if ((p = (dir <= 0) ? p.left : p.right) == null) {
                        HappyMap.Node<K, V> xpn = xp.next;
                        HappyMap.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)
                            ((HappyMap.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(HappyMap<K, V> map, HappyMap.Node<K, V>[] tab,
                                      boolean movable) {
                int n;
                if (tab == null || (n = tab.length) == 0)
                    return;
                int index = (n - 1) & hash;
                HappyMap.TreeNode<K, V> first = (HappyMap.TreeNode<K, V>) tab[index], root = first, rl;
                HappyMap.TreeNode<K, V> succ = (HappyMap.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 || root.right == null ||
                        (rl = root.left) == null || rl.left == null) {
                    tab[index] = first.untreeify(map);  // too small
                    return;
                }
                HappyMap.TreeNode<K, V> p = this, pl = left, pr = right, replacement;
                if (pl != null && pr != null) {
                    HappyMap.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
                    HappyMap.TreeNode<K, V> sr = s.right;
                    HappyMap.TreeNode<K, V> pp = p.parent;
                    if (s == pr) { // p was s's direct parent
                        p.parent = s;
                        s.right = p;
                    } else {
                        HappyMap.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) {
                    HappyMap.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;
                }
    
                HappyMap.TreeNode<K, V> r = p.red ? root : balanceDeletion(root, replacement);
    
                if (replacement == p) {  // detach
                    HappyMap.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(HappyMap<K, V> map, HappyMap.Node<K, V>[] tab, int index, int bit) {
                HappyMap.TreeNode<K, V> b = this;
                // Relink into lo and hi lists, preserving order
                HappyMap.TreeNode<K, V> loHead = null, loTail = null;
                HappyMap.TreeNode<K, V> hiHead = null, hiTail = null;
                int lc = 0, hc = 0;
                for (HappyMap.TreeNode<K, V> e = b, next; e != null; e = next) {
                    next = (HappyMap.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> HappyMap.TreeNode<K, V> rotateLeft(HappyMap.TreeNode<K, V> root,
                                                             HappyMap.TreeNode<K, V> p) {
                HappyMap.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> HappyMap.TreeNode<K, V> rotateRight(HappyMap.TreeNode<K, V> root,
                                                              HappyMap.TreeNode<K, V> p) {
                HappyMap.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;
            }
    
            /**
             * 插入后的平衡操作
             *
             * @param root
             * @param x
             * @param <K>
             * @param <V>
             * @return
             */
            static <K, V> HappyMap.TreeNode<K, V> balanceInsertion(HappyMap.TreeNode<K, V> root,
                                                                   HappyMap.TreeNode<K, V> x) {
                x.red = true;
                for (HappyMap.TreeNode<K, V> xp, xpp, xppl, xppr; ; ) {
                    //空
                    if ((xp = x.parent) == null) {
                        x.red = false;
                        return x;
                    }
                    //root
                    else if (!xp.red || (xpp = xp.parent) == null) {
                        return root;
                    }
    
                    //左子树插入
                    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 {
                        //右子树插入
                        // 祖父结点不为空,并且颜色为红色时
                        if (xppl != null && xppl.red) {
                            xppl.red = false;
                            xp.red = false;
                            xpp.red = true;
                            x = xpp;
                        } else {
                            // 左子树插入
                            if (x == xp.left) {
                                root = rotateRight(root, x = xp);
                                xpp = (xp = x.parent) == null ? null : xp.parent;
                            }
                            // x 的父亲结点设置成黑色
                            if (xp != null) {
                                xp.red = false;
                                if (xpp != null) {
                                    xpp.red = true;
                                    // 左旋
                                    root = rotateLeft(root, xpp);
                                }
                            }
                        }
                    }
                }
            }
    
            static <K, V> HappyMap.TreeNode<K, V> balanceDeletion(HappyMap.TreeNode<K, V> root,
                                                                  HappyMap.TreeNode<K, V> x) {
                for (HappyMap.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 {
                            HappyMap.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 {
                            HappyMap.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(HappyMap.TreeNode<K, V> t) {
                HappyMap.TreeNode<K, V> tp = t.parent, tl = t.left, tr = t.right,
                        tb = t.prev, tn = (HappyMap.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;
            }
        }
    
    }
    
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  • 原文地址:https://www.cnblogs.com/the-fool/p/11054034.html
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