HashMap 的containsKey(Objec…

•  /a**
      * Returns true if this map contains a mapping forthe
      * specified key.
      *
      * @param  key   The key whose presence inthis map is to be tested
      * @return true if this map contains a mapping for thespecified
      * key.
      */
  
• 
  
•     publicboolean 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;
      }