L4-Abstract Classes,Interfaces and OOD principles-CSDN博客

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Intended Learning Outcomes

To understand abstract type.
To enforce a design protocol by using abstract classes or interfaces.
To know the similarities and differences between an abstract class and an
interface.
To become familiar with the process of program development.
To discover classes using CRC cards.
To understand the impacts of coupling to a system.
To learn the relationship types: association, aggregation, composition,
realization and generalization.(UML class diagram)
To understand design principles and guidelines

Interface Syntax

Similar to a class but contains only constants and abstract methods.
Using abstract modifier.

public interface InterfaceName{
   
	constant declarations;
	method signatures;
	}
public interface Stack{
   
	public static final int MAX_SIZE=100;
	public abstract int pop();
	public abstract void push(int e);
	}

Interface class is a special class:
- interfaces contain abstract methods which don’t define method bodies, you can’t create instances from an interface using the new as usual, but you can use an interface to declare a variable.