Constructor overloading is a concept of having more than one constructor with different parameters list, in such a way so that each constructor performs a different task. For e.g. Vector class has 4 types of constructors. If you do not want to specify the initial capacity and capacity increment then you can simply use default constructor of Vector class like this Vector v = new Vector(); however if you need to specify the capacity and increment then you call the parameterized constructor of Vector class with two int arguments like this: Vector v= new Vector(10, 5);

Constructor overloading Program :-

1. public class Student {  
2. //instance variables of the class  
3. int id;  
4. String name;  
5.   
6. Student(){  
7. System.out.println("this a default constructor");  
8. }  
9.   
10. Student(int i, String n){  
11. id = i;  
12. name = n;  
13. }  
14.   
15. public static void main(String[] args) {  
16. //object creation  
17. Student s = new Student();  
18. System.out.println(" Default Constructor values:  ");  
19. System.out.println("Student Id : "+s.id + " Student Name : "+s.name);  
20.   
21. System.out.println(" Parameterized Constructor values:  ");  
22. Student student = new Student(10, "David");  
23. System.out.println("Student Id : "+student.id + " Student Name : "+student.name);  
24. }  
25. }  

Output :-

this a default constructor

Default Constructor values:

Student Id : 0

Student Name : null

Parameterized Constructor values: 

Student Id : 10

Student Name : David