HashMap 的containsKey(Objec…

•  /a**
       * Returns true if this map contains a mapping for the
       * specified key.
       *
       * @param   key   The key whose presence in this map is to be tested
       * @return true if this map contains a mapping for the specified
       * key.
       */
  
• 
  
•     public boolean containsKey(Object key) {
          Object k = maskNull(key);
          int hash = hash(k.hashCode());
          int i = indexFor(hash, table.length);
          Entry e = table[i];
          while (e != null) {
              if (e.hash == hash && eq(k, e.key))
                  return true;
              e = e.next;
          }
          return false;
      }