Head First Java Chapter 8Tom Henricksen

Abstract Classabstract class Canine extends Animal {

public void roam() {}

}

Dog class extends Canine {

Abstract vs Concrete● Abstract

○ Canine canine = new Canine();

● Concrete

○ Dog dog = new Dog();

Abstract methods● No body

● Must override

public abstract void eat();

java.lang.Object● Extend Object

● Basic methods

● Can instantiate

○ Object o = new Object();

Object overuseArrayList<Object> list = new ArrayList<Object>();

list.add(dog);

Dog dog2 = list.get(0);

Method calls● Reference type

○ Dog dog = new Dog();

○ Object o = dog;

○ o.bark();

Use your methods● Object methods

● Polymorphism

○ Snowboard s = new Snowboar();

○ Object o = s;

Casting● Cast back

○ Dog d = (Dog)o;

○ d.bark();

● Instanceof

Interface● Similar to an abstract class

○ public interface Pet {...}

○ public Dog implements Pet {...}

Interface methods● No body

○ void play();

● Must implement

Invoking the Superclassvoid runReport() {

super.runReport();

}

Assignment

● Exercise 1

● Exercise 2

● Exercise 3

Interfaces

Interfaces

Interfaces

Super