public static String join(CharSequence separator,Iterable<String> strings){
  StringBuilder sb=new StringBuilder();
  boolean first=true;
  for (  String s : strings) {
    if (first) {
      first=false;
    }
 else {
      sb.append(separator);
    }
    sb.append(s);
  }
  return sb.toString();
}

public static String join ( CharSequence separator , Iterable < String > strings ) { StringBuilder sb = new StringBuilder ( ) ; boolean first = true ; for ( String s : strings ) { if ( first ) { first = false ; } else { sb . append ( separator ) ; } sb . append ( s ) ; } return sb . toString ( ) ; }
concatenates strings , using a separator .
