question: 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 ) ) ; }
target:  Tell whether the string contains a positive or negative number delta, i.e., a number with an obligatory + or - sign.