public PunctuationTrie<T> lookup(char ch){
  int i=Arrays.binarySearch(childMap,ch);
  return i >= 0 ? children[i] : null;
}

public PunctuationTrie < T > lookup ( char ch ) { int i = Arrays . binarySearch ( childMap , ch ) ; return i >= 0 ? children [ i ] : null ; }
the child corresponding to the given character .
