question: public static String toCommaDelimitedString ( Collection c ) { if ( c . isEmpty ( ) ) { throw new IllegalArgumentException ( ) ; } StringBuffer result = new StringBuffer ( ) ; for ( Iterator i = c . iterator ( ) ; i . hasNext ( ) ; ) { Object o = i . next ( ) ; result . append ( ", " + o . toString ( ) ) ; } return result . substring ( 1 ) ; }
target:  Returns the elements of c separated by commas. c must not be empty.