java8HashMap源码阅读

之前阅读java7及之前版本HashMap源码时候，没有看全，所以这次决定一个一个方法去看。

先说结论，看完了除TreeNode的部分，红黑树的操作太头疼了(主要是源码很多代码进行了合并之类的，效率高，可读性差)，还好我之前看过红黑树，关于红黑的，可以看我的另一个文章 算法导论之第十三章-红黑树

HashMap内部的数据结构
由Node组成的数组table，一般的构造器并不会生成table数组，而是在第一次put时，发现数组不存在，进行resize数组操作时，新建数组，默认16个长度
table每一格保存一个Node，Node为链表格式，如果链表长度过长(大于8时),链表要转化为TreeNode格式，树的格式，是红黑树(较平衡的树，而且保持平衡的代价不是特别高)，TreeNode节点变小时，也会转回Node
插入(put)：
1、判断是否存在(不存在跳转2、存在直接跳转3)
2、扩容
3、根据(hash&(n-1))的值，判断要插入的位置(n为table的长度)，如果插入的位置是空的，直接插入，插入操作结束，如果Node值不为空，判断待插入的值是否和插入位置上的值是否相等(使用equals比较)，相等就结束插入，否则进行4
4、如果原位置的Node属于TreeNode，跳转5，否则跳转6
5、在树中边判断是否和节点相等边找寻插入的位置，如果有相等，此次插入结束，否则找到相应位置进行插入，然后进行平衡操作操持树的平衡，跳转7
6、依次判断Node链表里的每个值是否和插入的值相等，如果存在相等的，直接进行结束，否则插入到最后一个节点的后部，插入成功之后，判断链表长度，长度过长，链表转成树，结束之后跳转7
7、确定有新插入的，就要进行size++操作，当size过大时(与threshold进行比较，threshold又与loadFactor有关)，要进行扩容操作
获取(get)：
1、根据(hash&(n-1))的值，找到table中对应的节点，如果节点为空，直接返回null，如果节点的key和搜索的key一样(euqals比较)，直接返回该节点的value，如果节点是TreeNode，执行2，否则，执行3
2、红黑树也是二叉树，递归执行，从根节点开始往下判断，比较hash值，直到找到节点
3、链表就用while循环判断，只是不停next而已
删除(remove):
1、类似get，找到要删除的node，如果node为空，直接结束，不为空，进行判断，如果为树，执行树的删除，执行2，否则执行正常删除，执行3
2、红黑树的删除比较麻烦，在这也说不完，总之就是要保持树的平衡
3、链表的删除就很简单，前后连在一起，那就删除了
4、既然删除了，size–不要忘记
扩容(resize):
1、扩容其实更多是和插入时候才有的，但是毕竟复杂，单列出来。扩容也不一定会扩，如果table的长度够长，那就不会进行扩容，需要扩容时，进行2
2、扩容分为几种，一种是原来是空的，现在建立一个初始数组(一般16个长度)，这种情况下，到此就结束了。如果原来数组不为空，那就进行翻倍处理
3、数组长度翻倍，那原来的值就要进行重新加入新的格子里了，如果原位置为空，继续为空，如果原位置就单独Node，直接移动到计算出的新位置，如果是链表，进行4，如果是TreeNode，进行5
4、首先明白一点，hash&(n-1)的计算，会让原来位置在k的节点，重新计算得到k或者k+n。所以我们最后最多也就2个链表，分别移动到新位置就行
5、树的扩容前一步和链表一致的，因为这里的TreeNode保持了链表的特性，有next和pre。分成两个链表之后，如果链表长度大于8，再调用链表转树的方法，那就完成扩容了
线程不安全之处
看到扩容的方法，应该很多人想到了，不安全就在扩容时候。如果两个线程同时插入，线程1扩容，线程2插入，线程1扩容时候遍历数组table，已经遍历完k位置了，这时候线程2把数值插入，线程1扩容结束，线程2的数值只是插入到原table，并没有进入新table。
但是java8有效解决了java7中hashmap的死链问题，因为之前插入时候的值是插入在链表的首位，现在是插入在末尾。

一、构造器
1、无参构造器，只做了一件事，把扩容指数loadFactor设定为默认值0.75(之所以是0.75，后面边看边理解)

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

2、带有initialCapacity和loadFactor的构造器。

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))
		//大概意思就是怕传入一些奇怪的值，例如：0.0f/0.0f
        throw new IllegalArgumentException("Illegal load factor: " +
                                           loadFactor);
    this.loadFactor = loadFactor;
	//设置需要准备size的大小
    this.threshold = tableSizeFor(initialCapacity);
}

/**
 * 这个接口的目的就是找到与cap最接近的大于等于cap的且是2的指数的值
 * 例如传入5，返回8，传入19返回32
 */
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;
}

3、只带initialCapacity的构造器

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

4、传参是Map的构造器

public HashMap(Map<? extends K, ? extends V> m) {
    this.loadFactor = DEFAULT_LOAD_FACTOR;
    putMapEntries(m, false);
}

//将map值录入到this中
final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
	//获取需要插入map的size
    int s = m.size();
    if (s > 0) {
        if (table == null) { // pre-size
			//如果table为空
            float ft = ((float)s / loadFactor) + 1.0F;
            int t = ((ft < (float)MAXIMUM_CAPACITY) ?
                     (int)ft : MAXIMUM_CAPACITY);
            if (t > threshold)
				//设置table的数组大小
                threshold = tableSizeFor(t);
        }
        else if (s > threshold)
			//扩容操作
            resize();
        for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
            K key = e.getKey();
            V value = e.getValue();
			//把数据录入
            putVal(hash(key), key, value, false, evict);
        }
    }
}

上面代码中的扩容和插入方法，会在后面介绍

二、插入

 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<K,V>[] tab; Node<K,V> p; int n, i;
        if ((tab = table) == null || (n = tab.length) == 0)
			//数组为空时
            n = (tab = resize()).length;
        if ((p = tab[i = (n - 1) & hash]) == null)
			//进行hash计算后的位置上是空的，那就很简单了，直接放到上面去
            tab[i] = newNode(hash, key, value, null);
        else {
            Node<K,V> e; K k;
            if (p.hash == hash &&
                ((k = p.key) == key || (key != null && key.equals(k))))
				//已有存在，那就不进行不操作了
                e = p;
            else if (p instanceof TreeNode)
				//如果是树，按树的方法走
                e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
            else {
                for (int binCount = 0; ; ++binCount) {
                    if ((e = p.next) == null) {
						//把值插入到最后
                        p.next = newNode(hash, key, value, null);
						//次数多于8-1时，将链表转化成树
                        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))))
						//插入的和链表中某一个key是一样的，就结束循环
                        break;
                    p = e;
                }
            }
            if (e != null) { // existing mapping for key
				//e!=null表明是并没有插入，因为存在重复
                V oldValue = e.value;
                if (!onlyIfAbsent || oldValue == null)
                    e.value = value;
				//好像和LinkedHashMap有关
                afterNodeAccess(e);
				//没有插入插入成功，那就直接返回，不用执行之后的代码了
                return oldValue;
            }
        }
		//只是记录下，fail-fast机制需要
        ++modCount;
        if (++size > threshold)
            resize();
        afterNodeInsertion(evict);
        return null;
    }	
	
	//建树
	final void treeifyBin(Node<K,V>[] tab, int hash) {
        int n, index; Node<K,V> e;
        if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
            resize();
        else if ((e = tab[index = (n - 1) & hash]) != null) {
            TreeNode<K,V> hd = null, tl = null;
            do {
				//下面的操作是把数值插入链表中
                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)
				//把链表变成树
                hd.treeify(tab);
        }
    }

三、获取

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

final Node<K,V> getNode(int hash, Object key) {
    Node<K,V>[] tab; 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 TreeNode)
				//树的情况去TreeNode执行
                return ((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;
}

四、删除

public V remove(Object key) {
        Node<K,V> e;
        return (e = removeNode(hash(key), key, null, false, true)) == null ?
            null : e.value;
    }
	
    public boolean remove(Object key, Object value) {
        return removeNode(hash(key), key, value, true, true) != null;
    }
	
	
    final Node<K,V> removeNode(int hash, Object key, Object value,
                               boolean matchValue, boolean movable) {
        Node<K,V>[] tab; Node<K,V> p; int n, index;
        if ((tab = table) != null && (n = tab.length) > 0 &&
            (p = tab[index = (n - 1) & hash]) != null) {
            Node<K,V> node = null, e; K k; V v;
			//先找到要删除的节点node
            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)
					//树的话去树那查看
                    node = ((TreeNode<K,V>)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);
                }
            }
			//再进行删除
            if (node != null && (!matchValue || (v = node.value) == value ||
                                 (value != null && value.equals(v)))) {
                if (node instanceof TreeNode)
					//树的删除
                    ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
                else if (node == p)
					//节点为开头
                    tab[index] = node.next;
                else
                    p.next = node.next;
				//只是记录下，fail-fast机制需要
                ++modCount;
                --size;
				//同样，和LinkedHashMap有关
                afterNodeRemoval(node);
                return node;
            }
        }
        return null;
    }

五、扩容

//扩容操作
	final Node<K,V>[] resize() {
		//记录老数组
        Node<K,V>[] oldTab = table;
		//老的数组长度
        int oldCap = (oldTab == null) ? 0 : oldTab.length;
		//老的数组长度
        int oldThr = threshold;
        int newCap, newThr = 0;
        if (oldCap > 0) {
            if (oldCap >= MAXIMUM_CAPACITY) {
				//老的数组长度已经达到上限，就不再扩容了
                threshold = Integer.MAX_VALUE;
                return oldTab;
            }
            else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                     oldCap >= DEFAULT_INITIAL_CAPACITY)
				//数组长度*2
                newThr = oldThr << 1; // double threshold
        }
        else if (oldThr > 0) // initial capacity was placed in threshold
			//此时原数组是空的，但是原threshold是有的，那就建一个和threshold相等的数组就行
            newCap = oldThr;
        else {               // zero initial threshold signifies using defaults
            newCap = DEFAULT_INITIAL_CAPACITY;
			//默认扩容因子*默认数组长度
            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;
		//建新的数组
        @SuppressWarnings({"rawtypes","unchecked"})
            Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
        table = newTab;
		//如果oldTab为null，那就没有扩容必要，直接给个空数组回去就行
        if (oldTab != null) {
            for (int j = 0; j < oldCap; ++j) {
                Node<K,V> e;
                if ((e = oldTab[j]) != null) {
                    oldTab[j] = null;//旧的节点置空
                    if (e.next == null)
						//如果原来节点只有一个值，就将其移动至新的数组中就行
                        newTab[e.hash & (newCap - 1)] = e;
                    else if (e instanceof TreeNode)
						//如果节点已经是二叉树了，走二叉树的流程
                        ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
                    else { // preserve order
						//走到这的都是链表
						//lo即为low，偏小
                        Node<K,V> loHead = null, loTail = null;
						//hi即为high，偏大
                        Node<K,V> hiHead = null, hiTail = null;
                        Node<K,V> next;
                        do {
							//把next取出来
                            next = e.next;
                            if ((e.hash & oldCap) == 0) {
								//其实这个判断和(e.hash & (newCap - 1))<oldCap是一致的，就是判断在新的数组的哪一部分
								//这就是在0-(oldCap-1)部分，即插入loHead列表
                                if (loTail == null)
                                    loHead = e;
                                else
                                    loTail.next = e;
                                loTail = e;
                            }
                            else {
								//这就是在oldCap-(newCap-1)部分，即插入hiHead列表
                                if (hiTail == null)
                                    hiHead = e;
                                else
                                    hiTail.next = e;
                                hiTail = e;
                            }
							//当next一直存在时，进行循环
                        } while ((e = next) != null);
						//下面的操作就是把列表放入table数组中了
                        if (loTail != null) {
                            loTail.next = null;
                            newTab[j] = loHead;
                        }
                        if (hiTail != null) {
                            hiTail.next = null;
                            newTab[j + oldCap] = hiHead;
                        }
                    }
                }
            }
        }
        return newTab;
    }

六、TreeNodede的方法

1、插入

	//TreeNode的put
    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的作用就是判断是走左节点还是右节点
                dir = -1;
            else if (ph < h)
                dir = 1;
            else if ((pk = p.key) == k || (k != null && k.equals(pk)))
				//重复
                return p;
            else if ((kc == null &&
                      (kc = comparableClassFor(k)) == null) ||
                     (dir = compareComparables(kc, k, pk)) == 0) {
				//不能比较，或者比较为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))
						 //如果能在左右节点找到，说明有重复，那就直接返回
                        return q;
                }
				//真的没法比了，那就比内存地址吧
                dir = tieBreakOrder(k, pk);
            }

            TreeNode<K,V> xp = p;
            if ((p = (dir <= 0) ? p.left : p.right) == null) {
				//如果要插入的地方是null，那就进行插入，否则进行循环
                Node<K,V> xpn = xp.next;
                TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
				//将节点放到目标的左边或者右边
                if (dir <= 0)
                    xp.left = x;
                else
                    xp.right = x;
				//next和pre的操作，和树没关系，其实只是保持这个树还是链表
                xp.next = x;
                x.parent = x.prev = xp;
                if (xpn != null)
                    ((TreeNode<K,V>)xpn).prev = x;
				//平衡红黑树，然后再检验
                moveRootToFront(tab, balanceInsertion(root, x));
                return null;
            }
        }
    }

2、扩容

	//该方法属于HashMap的内部类TreeNode，树进行扩容
	final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
		//这一步就是准备好要拆开的树
        TreeNode<K,V> b = this;
        // Relink into lo and hi lists, preserving order
		//很明确，把两个新树准备好
        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) {
			//TreeNode应该还保留了链表的部分特性，有next
            next = (TreeNode<K,V>)e.next;
            e.next = null;
            if ((e.hash & bit) == 0) {
                if ((e.prev = loTail) == null)
                    loHead = e;
                else
					//把所有的值都先放入tail中
                    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)
				//当小于等于6时，把树改成链表
                tab[index] = loHead.untreeify(map);
            else {
                tab[index] = loHead;
                if (hiHead != null) // (else is already treeified)
					//那就把链表转成树(上面的操作还是链表)
                    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);
            }
        }
    }

3、删除

	//删除
    final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
                              boolean movable) {
        int n;
        if (tab == null || (n = tab.length) == 0)
			//tab为空
            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;
		//在链表里删除
        if (pred == null)
            tab[index] = first = succ;
        else
            pred.next = succ;
        if (succ != null)
            succ.prev = pred;
        if (first == null)
			//要删除的不存在，直接结束
            return;
        if (root.parent != null)
			//找到根节点
            root = root.root();
        if (root == null || root.right == null ||
            (rl = root.left) == null || rl.left == null) {
			//我也不知道为啥就这么几个判断，就能得出too small的结论，不过作为较平衡树，如果这样确实too small
			//既然too small，那就不要当树了，变回链表吧
            tab[index] = first.untreeify(map);  // too small
            return;
        }
        TreeNode<K,V> p = this, pl = left, pr = right, replacement;
        if (pl != null && pr != null) {
			//左右节点都不为空时
            TreeNode<K,V> s = pr, sl;
			//sl是右节点的左节点
            while ((sl = s.left) != null) // find successor
                s = sl;
			//s为(右节点的左节点或者右节点)
			//下面三部的操作是交换p和s的颜色
            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
				//如果右节点没有左节点
                p.parent = s;
                s.right = p;
            }
            else {
				//右节点有左节点
                TreeNode<K,V> sp = s.parent;//sp是p的右节点
                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)
			//右节点为空
            replacement = pl;
        else if (pr != null)
			//左节点为空
            replacement = pr;
        else
			//两个节点都是空的
            replacement = p;
        if (replacement != p) {
			//下面这个操作，就是把p从树中移除了
            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;
        }

		//如果p是黑节点，需要进行保持平衡操作
        TreeNode<K,V> r = p.red ? root : balanceDeletion(root, replacement);

        if (replacement == p) {  // detach
			//如果p是叶节点，直接删除
            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);
    }

4、树改链表

	//树改成链表代码
	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) {
			//this现在就是个链表，所以直接转成Node就行
            Node<K,V> p = map.replacementNode(q, null);
            if (tl == null)
                hd = p;
            else
                tl.next = p;
            tl = p;
        }
        return hd;
    }

5、链表改成树

	//链表改成树
	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);
    }

6、把root设置为链表的头结点

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

7、搜索

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

	//找位置
    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)
				//hash偏小居左
                p = pl;
            else if (ph < h)
				//hash偏大居左
                p = pr;
            else if ((pk = p.key) == k || (k != null && k.equals(pk)))
				//值对了
                return p;
            else if (pl == null)
				//左树空了在判断右树
                p = pr;
            else if (pr == null)
				//右树为空判断左树
                p = pl;
            else if ((kc != null ||
                      (kc = comparableClassFor(k)) != null) &&
                     (dir = compareComparables(kc, k, pk)) != 0)
				//对象是否可比较，如果可以，获取比较的值
                p = (dir < 0) ? pl : pr;
            else if ((q = pr.find(h, k, kc)) != null)
				//先搜左树
                return q;
            else
				//再搜右树
                p = pl;
        } while (p != null);
        return null;
    }

8、查root

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

9、比较内存的hash值

	//这是在比较内存地址？
    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;
    }

10、插入后保持树的平衡

	//插入后保持树的平衡
    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);
                        }
                    }
                }
            }
        }
    }

11、删除后保持树的平衡

	//删除后保持树的平衡
    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;
                    }
                }
            }
        }
    }

12、左旋

	//左旋
    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;
    }

13、右旋

	//右旋
    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;
    }

14、检查树是否正常

	//检查树是否正常
	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)
			//t的前节点的后节点不是自己
            return false;
        if (tn != null && tn.prev != t)
			//t的后节点的前节点不是自己
            return false;
        if (tp != null && t != tp.left && t != tp.right)
			//t的父节点的左右节点都不是自己
            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;
    }

七、其他

//对象是否可比较(这个不是重点，不在这上面花时间了)
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;
}

//进行比较
static int compareComparables(Class<?> kc, Object k, Object x) {
    return (x == null || x.getClass() != kc ? 0 :
            ((Comparable)k).compareTo(x));
}