HIT软件构造笔记 面向对象的编程（Object-Oriented Programming (OOP)）

面向对象的编程（Object-Oriented Programming (OOP)）

考点：小的知识点，多看例子，都是纠错程序

基础概念Basic concepts: object, class, attribute, and method

类成员、class methods类方法、instance methods实例方法、实例成员变量

共享栈与新建栈的区别

所有和类中的对象相关的数据（即使是基本数据类型）都存在堆里；方法里的基本数据类型存在栈里–考

下图不考

接口Interface

– Interface和Class: 定义和实现ADT；也可以不需要接口直接使用类作为ADT，既 有ADT定义也有ADT实现；实际中更倾向于使用接口来定义变量

– 接口之间可以继承与扩展

– 一个类可以实现多个接口（从而具备了多个接口中的方法）现在支持接口中的方法

– 一个接口可以有多种实现类

！java不允许实现多重继承的类，但是接口可以实现多重继承

Set :接口

继承：B中有的操作A中一定都要有，A包含B----程序员自己注意，没法检查

多态：1、重写2、重载3、泛型

设计一个好的类Designing good classes

Advantages of immutable classes

immutable对象可以多个引用中share(反正改变不了其它的引用值)

§ Simplicity
§ Inherently Thread-Safe
§ Can be shared freely
§ No need for defensive copies
§ Excellent building blocks

How to write an immutable class

§ Don’t provide any mutators
§ Ensure that no methods may be overridden
§ Make all fields final
§ Make all fields private
§ Ensure security of any mutable components (avoid rep exposure)
§ Implement toString(), hashCode(), clone(), equals(), etc.

When to make classes immutable什么时候要immutable类型的类

§ Always, unless there’s a good reason， not to经常会改变值的类就设置成mutable
§ Always make small “value classes” immutable!
– Examples: Color, PhoneNumber, Unit
– Date and Point were mistakes!
– Experts often use long instead of Date

When to make classes mutable什么时候要mutable类型的类

§ Class represents entity whose state changes
– Real-world - BankAccount, TrafficLight
– Abstract - Iterator, Matcher, Collection
– Process classes - Thread, Timer
§ If class must be mutable, minimize mutability
– Constructors should fully initialize instance
– Avoid reinitialize methods

Summary

§ Criteria of Object-Orientation
§ Basic concepts: object, class, attribute, method, and interface
§ Distinct features of OOP
Encapsulation and information hiding
Inheritance and overriding
Polymorphism, subtyping and overloading
Static and Dynamic dispatch
§ Some important Object methods in Java
§ To write an immutable class
§ History of OOP
§ Summary
tant Object methods in Java
§ To write an immutable class
§ History of OOP
§ Summary