public static String join(CharSequence sep,Iterable<? extends CharSequence> items){
  StringBuilder sb=new StringBuilder();
  join(sb,sep,items);
  return sb.toString();
}

public static String join ( CharSequence sep , Iterable < ? extends CharSequence > items ) { StringBuilder sb = new StringBuilder ( ) ; join ( sb , sep , items ) ; return sb . toString ( ) ; }
join items on separator .
