Java数据结构-HashMap详解

时间:2022-09-13 12:16:18

java数据结构-hashmap

1. hashmap数据结构

没有哈希冲突时,为数组,支持动态扩容

Java数据结构-HashMap详解

哈希冲突时,分为两种情况:

1.当冲突长度小于8或数组长度小于64(min_treeify_capacity默认值为64)时,为数组+链表(node)

2.当冲突长度大于8时,为数组+红黑树/链表(treenode)。

红黑树用于快速查找,链表用于遍历。

Java数据结构-HashMap详解

2. 红黑树

hashmap中的treenode是红黑树的实现。

treenode几个方法

1. 左旋转

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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;
    }

实现效果如图

Java数据结构-HashMap详解

2. 右旋转

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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;
    }

实现效果如图

Java数据结构-HashMap详解

3. 插入

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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) //①
          return root;
        if (xp == (xppl = xpp.left)) {
          if ((xppr = xpp.right) != null && xppr.red) { //②
            xppr.red = false;
            xp.red = false;
            xpp.red = true;
            x = xpp;
          }
          else {
            if (x == xp.right) { //③
              root = rotateleft(root, x = xp);
              xpp = (xp = x.parent) == null ? null : xp.parent;
            }
            if (xp != null) { //④
              xp.red = false;
              if (xpp != null) {
                xpp.red = true;
                root = rotateright(root, xpp);
              }
            }
          }
        }
        else {
          if (xppl != null && xppl.red) { //②
            xppl.red = false;
            xp.red = false;
            xpp.red = true;
            x = xpp;
          }
          else {
            if (x == xp.left) {    //⑤
              root = rotateright(root, x = xp);
              xpp = (xp = x.parent) == null ? null : xp.parent;
            }
            if (xp != null) {  //⑥
              xp.red = false;
              if (xpp != null) {
                xpp.red = true;
                root = rotateleft(root, xpp);
              }
            }
          }
        }
      }
    }

实现效果如下:

Java数据结构-HashMap详解

Java数据结构-HashMap详解

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原文链接:https://www.cnblogs.com/huiyao/p/10549752.html