code: public boolean containsValue(Object value) {
          Object[] tab = table;
          for (int i = 1; i < tab.length; i += 2)
              if (tab[i] == value && tab[i - 1] != null)
                  return true;
  
          return false;
      }
docs: Tests whether the specified object reference is a value in this identity
  hash map.
  
  @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 object reference
  @see     #containsKey(Object)