question: protected int determineIndex ( String s , int numAttributes ) throws Exception { int result ; if ( s . equals ( "first" ) ) { result = 0 ; } else if ( s . equals ( "last" ) ) { result = numAttributes - 1 ; } else { result = Integer . parseInt ( s ) - 1 ; } if ( ( result < 0 ) || ( result > numAttributes - 1 ) ) { throw new IllegalArgumentException ( "'" + s + "' is not a valid index for the range '1-" + numAttributes + "'!" ) ; } return result ; }
target:  parses the index string and returns the corresponding int index