when is constructor used in java code example

Example 1: constructor in java

A constructor is a special method used to initialize objects in java.
we use constructors to initialize all variables in the class 
when an object is created. As and when an object
is created it is initialized automatically with the help of 
constructor in java.
  
We have two types of constructors:
Default Constructor
Parameterized Constructor

public classname(){
}
public classname(parameters list){
}

Example 2: constructor in java

public class ConstructorDemo
{
   int a;
   ConstructorDemo()
   {
      a = 26;
   }
   public static void main(String[] args)
   {
      ConstructorDemo obj = new ConstructorDemo();
      System.out.println(obj.a);
   }
}