public V get(Object key) {    Node
    
      e;    return (e = getNode(hash(key), key)) == null ? null : e.value;}final Node
     
       getNode(int hash, Object key) {    Node
      
       [] tab;    Node
       
         first, e;     int n;     K k;    //如果table数组不为空 且 该键值对对应的位置存有node节点        if ((tab = table) != null && (n = tab.length) > 0 && (first = tab[(n - 1) & hash]) != null) {        if (first.hash == hash && ((k = first.key) == key || (key != null && key.equals(k))))            return first;        //如果table中存储的键值对不是要查找的这对，就从该桶的链中查找        if ((e = first.next) != null) {                    if (first instanceof TreeNode)                return ((TreeNode
        
         )first).getTreeNode(hash, key);            do {                if (e.hash == hash && ((k= e.key) == key || (key != null && key.equals(k))))                    return e;            } while ((e = e.next) != null);        }    }    return null;//该键值对不存在}