corejava-OOPs: What is the purpose of default constructor ?

Constructor is a special type of method that is used to initialize the object. Constructor is invoked at the time of object creation. It constructs the values i.e. provides data for the object that is why it is known as constructor.

Default constructor provides the default values to the object like 0, null etc. depending on the type.

Let´s see the following example :

class Student{  
int id;  
String name;  
 
void display(){System.out.println(id+" "+name);}  
 
public static void main(String args[]){  
Student s1=new Student();  
Student s2=new Student();  
s1.display();  
s2.display();  
}  
}  
It´ll give following output :
0 null  
0 null  

In the above class,you are not creating any constructor so compiler provides you a default constructor. Here 0 and null values are provided by default constructor.