软件设计模式ch5 - 单件模式.ppt

1、软件设计方法及设计模式,张聚礼 副教授/系统分析师,单 件 模 式,5,一,二,三,四,五,六,独一无二,剖析经典的单件模式实现,巧克力工厂,定义单件模式,线程问题,处理多线程,主要内容,一、独一无二,独一无二,小小单件,(一),(二),(一) 独一无二,如何创建一个对象？ 一旦有类，就可以多次创建。那么 等等，private构造器的类不能实例化。,(二) 小小单件,这样，如何呢？ 合在一起，就可以实例化了。,(二) 小小单件,二、剖析经典的单件模式实现,剖析经典的单件模式实现,看看这里,剖析经典的单件模式实现,三、巧克力工厂,巧克力锅炉,(一),(一) 巧克力锅炉,(一) 巧克力锅炉,(一)

2、 巧克力锅炉,四、定义单件模式,定义,类图,(一),(二),单件（Singleton）模式：确保一个类只有一个实例，并提供一个全局访问点。,(一) 定义,(二) 类图,五、线程问题,线程问题,JVM,(一),(二),(一) 线程问题,遇到麻烦了,(二) JVM,现在，扮演JVM角色，判断出这两个线程是否能抓住不同的锅炉对象而扰乱代码。,六、处理多线程,处理多线程,改善多线程,(一),(二),(一) 处理多线程,(一) 处理多线程,(二) 改善多线程,可以有以下选择,(二) 改善多线程,七、总结,Abstraction Encapsulation Polymorphism Inheritance

3、,Encapsulate what varies. Favor composition over inheritence. Program to interfaces, not implementations.,Strategy - defines a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.,总结,OO Basics,OO Princip

4、les,OO Patterns,1,Observer - defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically,总结,OO Patterns,Strive for loosely coupled designs between objects that interact.,OO Principles,2,Decorator - Attach additiona

5、l responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.,总结,OO Patterns,Classes should be open for extension but closed for modification.,OO Principles,3,Abstract Factory - Provide an interface for creating families of related

6、 or depedent objects without specifying their concrete classes. Factory Method - Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to the subclasses.,总结,OO Patterns,Depend on abstractions. Do not depend on concrete classes.,OO Principles,4,Singleton - ensu