Post date: Nov 8, 2014 6:48:37 PM

Starter

• SubClass extends SuperClass.
• SubClass inherits the members of SuperClass(instance variable and methods).
• SuperClass is more abstract while SubClass is more specific.
• IS-A test : SubClass IS-A SuperClass. e.g. Triangle is a shape.
• SubClass over-riding method can call the SuperClass version with keyword Super. Super.rotate();
• final method can't be over-ridden.

Polymorphism

• Dog mydog = new Dog();

1. Dog mydog Declares a reference variable on stack
2. new Dog() creates an object/instance on heap
3. = link the object and reference

• Animal mydog = new Dog();

Abstract Class

• It can't be instantiated or simply object of Abstract class can't be created.
• To use abstract class, it must be extended(inherited).
• It can be used as Reference Type to objects of concrete SubClass.

1. Extending the Abstract class:

    class ConcreteClass extends AbstractClass {}     AbstractClass c = new ConcreteClass();

2. Using Anonymous Class: To store the object/instance of anonymous inner Subclass of AbstractClass

    AbstractClass c = new  AbstractClass(){};

EDIT: You can of course not reuse the anonymous inner class, since it is anonymous and implicitly final, and the only place where an instance of it can be created is right here.

Abstract Method

• Abstract method has no body. public abstract void eat();
• The Class must be declared Abstract.
• The method must be over-ridden in the concrete SubClass.