private boolean isNumberDelta(String string){
  String s=string.trim();
  if (s.length() < 2)   return false;
  return (s.charAt(0) == '+' || s.charAt(0) == '-') && isUnsignedNumber(s.substring(1));
}

private boolean isNumberDelta ( String string ) { String s = string . trim ( ) ; if ( s . length ( ) < 2 ) return false ; return ( s . charAt ( 0 ) == '+' || s . charAt ( 0 ) == '-' ) && isUnsignedNumber ( s . substring ( 1 ) ) ; }
tell whether the string contains a positive or negative number delta , i . e . , a number with an obligatory + or - sign .
