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The CreateEmployee application sets the variable amount to 500 and invokes the
Employee class increment method with amount as an argument.
CreateEmployee
1 class CreateEmployee {
2
3 public static void main(String[] args) {
4 int amount = 500;
5
6 Employee fred = new Employee();
7 fred.increment(amount);
8 System.out.println("amount outside method: " + amount
);
9 }
10 }
The output of running the CreateEmployee application follows:
> java CreateEmployee
amount within method: 510
amount outside method: 500
CreateEmployee
So although the increment method has increased the amount to 510, the amount in the
calling program remains at 500.
If, however, the argument passed to a method is a reference data type, the memory address
of the argument is copied to the method's parameter. Consequently, both the calling method
argument and the called method parameter reference the same object. If the method
changes the value of this object, then this change is reflected in the calling program. To
illustrate this, the second version of Employee has the increment method modified to
accept an array argument, salary, of type int. The first element of salary is
incremented by 10.
Employee—second version
1 class Employee {
2
3 public void increment(int[] salary) {
4 salary[0] = salary[0] + 10;
5 System.out.println(''amount within method: " +
6 salary[0]);
7 }
8 }
Employee—second version