question: public static String join ( Collection < ? > col , String delim ) { if ( UtilValidate . isEmpty ( col ) ) return null ; StringBuilder buf = new StringBuilder ( ) ; Iterator < ? > i = col . iterator ( ) ; while ( i . hasNext ( ) ) { buf . append ( i . next ( ) ) ; if ( i . hasNext ( ) ) buf . append ( delim ) ; } return buf . toString ( ) ; }
target:  Creates a single string from a Collection of strings seperated by a delimiter.