1. Interfaces and Abstract Classes
I have wonderful news, mother. Joe finally implemented all his abstract methods! Now everything is working just the way we planned…

2. Abstract vs. Concrete Abstract Animal Concrete Canine Hippo Feline Dog
Wolf
Cat
Lion
Tiger

3. Abstract Classes You can not make a new instance of an abstract class!
Abstract public class Canine extends Animal {
public void roam() }
An abstract class means the class must be extended

4. It really sucks to be an abstract method. You don’t have a body.
Abstract Methods
public abstract void eat();
There is not a method body, end it with a semicolon
An interface includes abstract methods
An abstract method means it must be overridden
It really sucks to be an abstract method. You don’t have a body.

5. Making an Interface
A Java interface is like a 100% pure abstract class!
To define an Interface:
Public interface Pet {
public abstract void beFriendly();
public abstract void play(); }
All methods in an interface are abstract, so any class that is – A Pet MUST implement (i.e. override) the methods of Pet.

6. Showing the Pet Interface
Animal
Canine
Hippo
Feline
Dog
Wolf
Cat
Lion
Tiger

7. Implementing an Interface
public class Dog extends Canine implements Pet { public void beFriendly() {……} public void play() {……} public void roam() {……} public void eat() {…….} }
You must implement the pet methods!
These are just normal overriding methods.

8. Forget about animals! Flier Interface
What abstract methods would be needed for classes that fly
Classes that implement the flier interface could be:
Airplane
Ski jumper
????
Write out the interface and the classes that implement it.

9. Instance Variables
Does it make sense to say a Tub IS-A bathroom? Or a Bathroom IS-A Tub? Well it doesn’t to me. The relationship between my Tub and my Bathroom is HAS-A. Bathroom HAS-A Tub. That means Bathroom has a Tub instance variable.