Constructors

• Constructors are the functinalities which are going to be executed  automatically when the object is created.
•  Can be executed only once with respect to object
• Can't have any return type not even void.
• Name of the constructor should and must be always name of the class.
• Two types: default constructor and parametrized constructor

Default Constructor:

• A Constructor that have no parameters is known as Default Constructor.

 Example program for default constructor :

1. package com.instanceofjava;
2.  
3. public class MyDefaultConstructor{
4.  
5. public MyDefaultConstructor(){
6.  
7. System.out.println("I am inside default constructor");
8.  
9.  }
10.  
11. public static void main(String args[]){
12.  
13. MyDefaultConstructor mdc=new MyDefaultConstructor(); 
14.  
15. }
16. }
    

Output:

1. I am inside default constructor

Parameterized Constructor:

• A Constructor that have parameters is known as Parameterized Constructor.

Program for Parameterized Constructor:

1. package com.instanceofjava;
2.  
3. public class Employee{
4.  
5. private int id;
6. private String name;
7.  
8. Employee(int id,String name){
9.  this.id=id;
10. this.name=name;
11. }
12.  
13. public void display(){ 
14.  
15. System.out.println(id+" "+name); 
16.  
17. }
18.  
19. public static void  main (String args[]){
20.  
21. Emploee e=new Employee(1,"Indhu"); Employee e1=new Employee(2,"Sindhu"); e.display();
22. e1.display();
23.  
24. }
25. }

Output:

1. 1 Indhu 
2. 2 Sindhu