anchor.diff:      return putVal(hash(key), key, value, false, true);    //调用putVal()方法
   }
   ----
  -JDK1.8计算hash值::
  +JDK1.8计算hash值
   [source,java]
   ----
   static final int hash(Object key) {
  
positive.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没有初始化
      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;
  
negative.code: 
  ==== HashMap存取机制
  
  ===== 1.添加元素
  
  [source,java]
  ----
  