Abstract class example in java

public class First {

public static void main(String[] args) {
// TODO Auto-generated method stub
Second reff = new four();
reff.display();
reff.first();
}

}

public abstract class Second {

abstract void display();

abstract void first();

}

abstract class Third extends Second{

//abstract void first();

void display(){

System.out.println("Third method");

}

}

class four extends Third{

void first(){

System.out.println("four method");

}

}

output:-

Third method

four method