code: public final int getTrailValue(int leadvalue, char trail)
      {
          if (m_dataManipulate_ == null) {
              throw new NullPointerException(
                               "The field DataManipulate in this Trie is null");
          }
          int offset = m_dataManipulate_.getFoldingOffset(leadvalue);
          if (offset > 0) {
              return m_data_[getRawOffset(offset,
                                           (char)(trail & SURROGATE_MASK_))];
          }
          return m_initialValue_;
      }
docs: Get a value from a folding offset (from the value of a lead surrogate)
  and a trail surrogate.
  @param leadvalue the value of a lead surrogate that contains the
  folding offset
  @param trail surrogate
  @return trie data value associated with the trail character