Java + Android

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //Extends
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button bt = (Button) findViewById(R.id.button1);
        //Anonymous Class / Inner Class
        bt.setOnClickListener(new View.OnClickListener() {
            //Callback Function / Override
            public void onClick(View v) {
                //Method Chaining
                Toast.makeText(getBaseContext(), "Clicked", Toast.LENGTH_LONG).show();
            }
        });
    }
}

Extends
public class Init {
    public static void main(String[] args) {
        new Son();
    }
}

class Son extends Father {
    Son(){
        eat();
    }
}

class Father {
    public void eat(){
        System.out.println("Orange");
    }
}

Override
public class Init {
    public static void main(String[] args) {

        new Son();
    }
}

class Son implements Father {
    Son(){

    }

    @Override
    public void eat(){
        System.out.println("Apple");
    }
}

interface Father {
    public void eat();
}

Callback Function
public class Init {
    public static void main(String[] args) {

        Son cup = new Son();
        cup.drink(new Father(){     //Anonymous Class
            void eat(){         //Callback Function
                System.out.println("Apple");
            }
        });
    }
}

class Son {

    void drink(Father cup){
        cup.eat();
    }
}

class Father {

    void eat(){
    }
}
Anonymous Class
public class Init {
    public static void main(String[] args) {

        new Son();    //Anonymous class
    }
}

class Son {
    Son(){
        //drink("Coffee", new Father());
        drink("Coffee", new Father(){        //Anonymous class
            void eat(){
                System.out.println("Orange");
            }
        });
    }

    void drink(String cup1, Father cup2){
        System.out.println(cup2.Father(cup1));
        cup2.eat();
    }
}

class Father {
    String Father(String cup){
        return cup;
    }

    void eat(){
        System.out.println("Banana");
    }
}


Inner Class
public class Init {
    public static void main(String[] args) {

        new Son();
        new Son.Sson().eat();  // inner class
    }
}

class Son {
    Son(){
        System.out.println("Banana");
    }
    static class Sson{
        void eat(){
            System.out.println("Apple");
        }
    }
}


Method Chaining
public class Init {
    public static void main(String[] args) {

        new Son().drink().eat().desert();  //Method Chaining
    }
}

class Son {
    Son(){
    }

    Son drink(){
        System.out.println("Milk");
        return this;
    }

    Son eat(){
        System.out.println("Beef");
        return this;
    }

    void desert(){
        System.out.println("Cake");
    }
}