Abstract

For abstract method, the concret class must implement the body of it.

For example if we have Animal and Canine is abstract. Then Dog must implement all the abstract methods from both these class

Note: if Canine is abstract then it could implement the abstract method from Animal. If that happens, Dog doesn't need to implement anything.

Note: abstract method cannot be private.

When to use Abstract class, when to use Interface

Use:

• abstract class if you want to emphasize what the object is.
• interface if you want to emphasize what the object can do

For example, interface does not say that "wewewowo is the type of dog that can fly" but more like "this thing can fly"