工厂模式

/* * 工厂模式：工厂模式是一种创建型模式，目的是封装对象的创建过程，利用一个工厂类来“生产”对象，具体流程有工厂来负责。 * 工厂模式有三种：Simple Factory简单工厂模式，Factory Methods 工厂方法模式，Abstract Factory抽象工厂模式 *1）Simple Factory Pattern（简单工厂模式) *简单地把产生对象的代码封装成一个工厂类，具体生产出来的对象由参数决定，这个模式在创建对象时，利用的是switch或if语句等 *来做判断所生产的对象类型，由此使得该工厂类会涉及到了大量变动，当需要增加或减少一个类时，需要修改代码，随之带来将是很丑 *的代码。 *2）Factory Methods(工厂方法模式）就利用继承而不是利用判断语句实现，这种情况对工厂类修改不大，只需提供接口，具体类继承实现 *各自创建办法，而工厂类不需知道各类的创建。 起到隔离工厂类与实现类的作用。 *3）Abstract Factory(抽象工厂模式）提供了一个抽象工厂类，其他具体工厂类继承该抽象工厂类，实现多种产品的生产，而不是工厂方法提供 *的一种产品生产，即在生产产品的层次上加了一个抽象层。 * *在这章中提到了一个Dependency Inversion Principle（依赖倒置原则DIP） *:depend upon abstractions ,do not depend upon concrete classes *有点类似于Program to interface,not to implemention *提到的是依赖于抽象，不要依赖于具体类 *下面是DIP原则的重点： *A. HIGH LEVEL MODULES SHOULD NOT DEPEND UPON LOW LEVEL MODULES. BOTH SHOULD DEPEND UPON ABSTRACTIONS. *B. ABSTRACTIONS SHOULD NOT DEPEND UPON DETAILS. DETAILS SHOULD DEPEND UPON ABSTRACTIONS. *当设计依赖于低层时，构造一个抽象层，使设计依赖于此抽象层，这样可以提高代码的独立性，提高复用性。 *另外对这个原则，有三点指导性意见（guidelines) *1.no variable should hold a reference to an concrete class; *2.no class should derived from concrete class; *3.no method should overide an implemented method of any of its base class; * * *还有一个就是：如果对(”生产产品“接口）creator（下面的creteBread（）)使用static ，确实可以保证用类来产生产品 *但是static不可以继承，这时缺点。 * *下面是练习的两个例子，一个简单工厂模式，一个是工厂方法模式，抽象工厂模式（暂缺） *///1--------------------------Simple Factory Pattern----------------------------------abstract class Bread{private String _name;public Bread(String name){_name = name;}public void prepare(){System.out.println("prepare for " + _name);}public void bake(){System.out.println("baking.... ");}public void cut(){System.out.println("cut 4 piece");}public void pack(){System.out.println("packing.......");}}class BlackBread extends Bread{public BlackBread(){super("BlackBread");}}class WhiteBread extends Bread{public WhiteBread(){super("WhiteBread");}}class CheezeBread extends Bread{public CheezeBread(){super("CheezeBread");}}class BreadFactory{private Bread br;public static Bread createBread(String name){ //注意比较这个函数，在Factory Methods 与 Simple Factory的不同if(name == "BlackBread")return new BlackBread();elseif(name == "WhiteBread")return new WhiteBread();elsereturn new CheezeBread();}}public class BreadStore {/** * @param args */public static void main(String[] args) {// TODO 自动生成方法存根Bread br1 = BreadFactory.createBread("BlackBread");br1.prepare();br1.bake();br1.cut();br1.pack();System.out.println(".......................");Bread br2 = BreadFactory.createBread("WhiteBread");br2.prepare();br2.bake();br2.cut();br2.pack();}}//2-------------------------- Factory Methods Pattern----------------------------------abstract class Bread{String type;public Bread(String type){this.type = type;}public void prepare(){System.out.println("running prepare()" + type);}public void bake(){System.out.println("running bake()" + type);}public void cut(){System.out.println("running cut()" + type);}public void pack(){System.out.println("running pack()" + type);}}class BJBlackBread extends Bread{public BJBlackBread(){super("BJBlackBread");}}class BJWhiteBread extends Bread{public BJWhiteBread(){super("BJWhiteBread");}}class GZBlackBread extends Bread{public GZBlackBread(){super("GZBlackBread");}}class GZWhiteBread extends Bread{public GZWhiteBread(){super("GZWhiteBread");}}abstract class AbstractFactory{public abstract Bread createBread(String type);public void orderBread(String type){Bread bread = createBread(type);bread.prepare();bread.bake();bread.cut();bread.pack();}}class BJFactory extends AbstractFactory{public Bread createBread(String type){Bread bread;if(type == "BJBlackBread"){bread = new BJBlackBread();return bread;}else{bread = new BJWhiteBread();return bread;}}}class GZFactory extends AbstractFactory{public Bread createBread(String type){Bread bread;if(type == "GZBlackBread"){bread = new GZBlackBread();return bread;}else{bread = new GZWhiteBread();return bread;}}}public class Factory_Test{public static void main(String args[]){AbstractFactory BJfactory = new BJFactory();BJfactory.orderBread("BJBlackBread");System.out.println("---------------------------------");AbstractFactory GZfactory = new GZFactory();GZfactory.orderBread("GZBlackBread");}}