Question

What are the two ways of invoking functions?

Answer 1

The two ways of invoking functions in java are

• Call by value
• Call by reference.

Call by value is a method of invoking by passing the copy of actual parameters to the formal one.

Example: 
1. class Sample
2. {
3. void accept(int a, int b)
4. {
5. int sum = a + b;
6. System.out.println(sum);
7. }
8. public static void main (String args[])
9. {
10. int a = 6;
11. int b = 10;
12. Sample obj = new Sample();
13. obj.accept(a,b);
14. }

Call by reference is another method of invoking in java by passing the actual reference to the formal parameters. You can find any changes in the actual parameter that is reflected from the formal one.  

Example: 
1. class Sample1 
2. {
3. void Add(int x[])
4. {
5. int i, p;
6. p = x.length;
7. for (i = 0; i < p; i++)
8. {
9. System.out.print(x[i] + " ");
10. System.out.println();
11. }
12. }
13. public static void main (String args[])
14. {
15. int a[] = {3, 6, 8, 9};
16. int j, q;
17. q = a.length;
18. Sample2 obj = new Sample2();
19. obj.Add(a);
20. System.out.println("The arguments after function call: ");
21. for (j = 0; j < q; j++)
22. {
23. System.out.println(a[j] + " ");
24. System.out.println();
25. }
26. }