Can we overload constructor in java?

Problem statement:
You are given a code for constructor overloading. What do you think, can we overload the constructor in java?

Ans: Yes.

1. class A {
2. A() {
3. System.out.println("default");
4. }
5. A(int id) {
6. System.out.println("id");
7. }
8. A(int id, String name) {
9. System.out.println("id & name");
10. }
11. A(String name, Double salary) {
12. System.out.println("name & salary");
13. }
14. }
15. public class Sample {
16. public static void main(String[] args) {
17. A a = new A();
18. }
19. }

Output:

default

Can we override constructor in java?

Problem statement:
You are given a code for constructor overriding. What do you think, can we override the constructor in java?

Ans: No.

1. class A {
2. A() {
3. System.out.println("A of A");
4. }
5. }
6. class B extends A {
7. A() {
8. System.out.println("A of B");
9. }
10. }
11. public class Sample {
12. public static void main(String[] args) {
13. B b = new B();
14. }
15. }

Output:

Return type of method is missing, meaning compiler is treating A() as a method not as a constructor and also compiler is expecting return type for the method A(), because in code there is no return type.

what is the output of the code?

Problem statement:
Given the code for constructor overloading. What will be the output?

1. public class ConstructorCall {
2.     ConstructorCall() {
3.         System.out.println("default constructor");
4.     }
5.     ConstructorCall(int a){
6.         this();
7.         System.out.println("parameterized constructor");
8.         System.out.println(10);
9.     }
10.     public static void main(String[] args) {
11.         ConstructorCall st = new ConstructorCall(3);
12.     }
13. }

Output:

default constructor

parameterized constructor

10

Can we have final constructor in java class?

Problem statement:
Can we have final constructor in java class?

No ! we cannot have final constructor in java class.

1. public class NoFinalConstructor {
2.     public final NoFinalConstructor() {
3.         System.out.println("default");
4.     }
5.     public static void main(String[] args) {
6.         NoFinalConstructor st = new NoFinalConstructor();
7.     }
8. }

Output: compile time error - modifier 'final' is not allowed.