code: public boolean containsValue(Object value) {
          for (LinkedHashMapEntry<K,V> e = head; e != null; e = e.after) {
              V v = e.value;
              if (v == value || (value != null && value.equals(v)))
                  return true;
          }
          return false;
      }
docs: Returns <tt>true</tt> if this map maps one or more keys to the
  specified value.
  
  @param value value whose presence in this map is to be tested
  @return <tt>true</tt> if this map maps one or more keys to the
  specified value