public PunctuationTrie<T> lookup(CharSequence s){
  PunctuationTrie<T> t=this;
  for (int i=0, n=s.length(); i < n; ++i) {
    t=t.lookup(s.charAt(i));
    if (null == t) {
      break;
    }
  }
  return t;
}

public PunctuationTrie < T > lookup ( CharSequence s ) { PunctuationTrie < T > t = this ; for ( int i = 0 , n = s . length ( ) ; i < n ; ++ i ) { t = t . lookup ( s . charAt ( i ) ) ; if ( null == t ) { break ; } } return t ; }
the descendant of this trie corresponding to the string for this trie appended with s .
