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核心的数据结构是TreeNode和TreeBin,其余与HashMap相同
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# TreeNode
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treeNode就是红黑树结构
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# TreeBin
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是TreeNode的容器，提供转换黑红树的一些条件和锁的控制。通过读写锁来实现线程安全。
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```java
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static final class TreeBin<K,V> extends Node<K,V> {
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TreeNode<K,V> root;
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volatile TreeNode<K,V> first;
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volatile Thread waiter;
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volatile int lockState;
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// values for lockState
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static final int WRITER = 1; // 持有写锁
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static final int WAITER = 2; // 等待写锁
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static final int READER = 4; // 读锁
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/**
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* Tie-breaking utility for ordering insertions when equal
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* hashCodes and non-comparable. We don't require a total
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* order, just a consistent insertion rule to maintain
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* equivalence across rebalancings. Tie-breaking further than
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* necessary simplifies testing a bit.
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*/
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static int tieBreakOrder(Object a, Object b) {
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int d;
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if (a == null || b == null ||
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(d = a.getClass().getName().
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compareTo(b.getClass().getName())) == 0)
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d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
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-1 : 1);
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return d;
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}
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/**
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* Creates bin with initial set of nodes headed by b.
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*/
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TreeBin(TreeNode<K,V> b) {
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super(TREEBIN, null, null, null);
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this.first = b;
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TreeNode<K,V> r = null;
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for (TreeNode<K,V> x = b, next; x != null; x = next) {
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next = (TreeNode<K,V>)x.next;
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x.left = x.right = null;
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if (r == null) {
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x.parent = null;
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x.red = false;
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r = x;
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}
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else {
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K k = x.key;
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int h = x.hash;
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Class<?> kc = null;
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for (TreeNode<K,V> p = r;;) {
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int dir, ph;
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K pk = p.key;
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if ((ph = p.hash) > h)
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dir = -1;
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else if (ph < h)
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dir = 1;
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else if ((kc == null &&
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(kc = comparableClassFor(k)) == null) ||
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(dir = compareComparables(kc, k, pk)) == 0)
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dir = tieBreakOrder(k, pk);
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TreeNode<K,V> xp = p;
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if ((p = (dir <= 0) ? p.left : p.right) == null) {
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x.parent = xp;
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if (dir <= 0)
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xp.left = x;
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else
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xp.right = x;
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r = balanceInsertion(r, x);
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break;
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}
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}
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}
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}
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this.root = r;
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assert checkInvariants(root);
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}
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``` |
