HashMap1.8源码分析(红黑树)

转载：https://segmentfault.com/a/1190000012926722?utm_source=tag-newest

https://blog.csdn.net/weixin_40255793/article/details/80748946(方法全面)

方法

treeifyBin(普通节点链表转换成树形节点链表)

static final int TREEIFY_THRESHOLD = 8;

/**
 * 当桶数组容量小于该值时，优先进行扩容，而不是树化
 */
static final int MIN_TREEIFY_CAPACITY = 64;

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);
    }
}

/**
 * 将普通节点链表转换成树形节点链表
 */
final void treeifyBin(Node<K,V>[] tab, int hash) {
    int n, index; Node<K,V> e;
    // 桶数组容量小于 MIN_TREEIFY_CAPACITY，优先进行扩容而不是树化
    if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
        resize();
    else if ((e = tab[index = (n - 1) & hash]) != null) {
        // hd 为头节点（head），tl 为尾节点（tail）
        TreeNode<K,V> hd = null, tl = null;
        do {
            // 将普通节点替换成树形节点
            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);  // 将普通链表转成由树形节点链表
        if ((tab[index] = hd) != null)
            // 将树形链表转换成红黑树
            hd.treeify(tab);
    }
}

TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
    return new TreeNode<>(p.hash, p.key, p.value, next);
}

View Code