anchor.diff:      return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
   }
   ----
  -JDK1.7计算hash值::
  +JDK1.7计算hash值
   [source,java]
   ----
   final int hash(Object k) {
  
positive.code:      */
      if ((p = tab[i = (n - 1) & hash]) == null)
          /*
           * 当这里是空桶位时，就直接构造新的Node节点，将其放入桶位中
           * newNode()方法，就是对new Node(,,,)的包装
           * 同时也可以看到Node中的hash值就是重新计算的hash(key)
           */
          tab[i] = newNode(hash, key, value, null);
      else {
          //桶位不为空时
          Node<K,V> e; K k;
          if (p.hash == hash && ((k = p.key) == key || (key != null && key.equals(k))))
              //当存放元素的hash、key、value和桶位的元素都相等时，原来的p赋给e；
              e = p;
          else if (p instanceof TreeNode)
              // 如果存放的元素不等于原来桶位的元素，判断原来元素p是否是红黑树，如果是，把存放元素按红黑树存放
              e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
          else {
              // 如果原来的元素p是链表结构，按链表方式存储
              for (int binCount = 0; ; ++binCount) {
                  if ((e = p.next) == null) {
                      p.next = newNode(hash, key, value, null);
                      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))))
                      break;
                  p = e;
              }
          }
          if (e != null) { // existing mapping for key
              V oldValue = e.value;
              if (!onlyIfAbsent || oldValue == null)
                  e.value = value;
              afterNodeAccess(e);
              return oldValue;
          }
      }
      ++modCount;
      if (++size > threshold)
          resize();
      afterNodeInsertion(evict);
      return null;
  }
  ----
  
  
  
  
  ssh luotong@101.200.210.70
  
negative.code: ----
  final V putVal(int hash, K key, V value, boolean onlyIfAbsent, boolean evict) {
      Node<K,V>[] tab; Node<K,V> p; int n, i;
      //table未初始化或者长度为0，进行扩容
      if ((tab = table) == null || (n = tab.length) == 0)
          //可以看到put元素时，如果数组没有初始化，会调用resize()方法进行初始化。后面分析resize()方法
          n = (tab = resize()).length;
  