class Employee {
   private String name;
   private double salary;

   public Employee(String n, double s) {
      name = n;
      salary = s;
   }

   public String toString() {
      return name + " ($" + salary + ") ";
   }

   private static void swapEmployee(Employee e1, Employee e2) {
      Employee temp = e1; // Cannot really swap caller's arguments
      e1 = e2; 
      e2 = temp;
   }

   private static void swapSalary(Employee e1, Employee e2) {
      double temp = e1.salary; // OK: Can swap the instance fields 
      e1.salary = e2.salary; 
      e2.salary = temp; 
   }

   public static void main(String[] args) // unit test for Employee class
   {
      Employee a = new Employee("Harry", 10000);
      Employee b = new Employee("Helena", 20000);

      Employee.swapEmployee(a, b); // No change: a still refers Harry; b still refers Helena
      Employee.swapSalary(a, b); // Changed! salaries swapped
      System.out.println(a);
      System.out.println(b);
   }
}