code: public boolean containsValue(Object value) {
          for (TreeMapEntry<K,V> e = getFirstEntry(); e != null; e = successor(e))
              if (valEquals(value, e.value))
                  return true;
          return false;
      }
docs: Returns {@code true} if this map maps one or more keys to the
  specified value.  More formally, returns {@code true} if and only if
  this map contains at least one mapping to a value {@code v} such
  that {@code (value==null ? v==null : value.equals(v))}.  This
  operation will probably require time linear in the map size for
  most implementations.
  
  @param value value whose presence in this map is to be tested
  @return {@code true} if a mapping to {@code value} exists;
  {@code false} otherwise
  @since 1.2