code: public CharsTrie resetToState(State state) {
          if(chars_==state.chars && chars_!=null && root_==state.root) {
              pos_=state.pos;
              remainingMatchLength_=state.remainingMatchLength;
          } else {
              throw new IllegalArgumentException("incompatible trie state");
          }
          return this;
      }
docs: Resets this trie to the saved state.
  @param state The State object which holds a saved trie state.
  @return this
  @throws IllegalArgumentException if the state object contains no state,
  or the state of a different trie
  @see #saveState
  @see #reset