public static void main ( ) {
System.out.println ( "output = " + numberStack ( 4 ) ) ;
}
public static String numberStack ( int n ) {
if ( n <= 0) {
System.out.println ( ) ;
return "" ;
}
System.out.println ( n ) ;
numberStack ( n -1 ) ;
System.out.println ( n ) ;
return "done";
}