09_工厂和单例模式_思路与案例.doc

简单工厂模式农场（FruitGardener）生产的水果（Fruit）有三种：葡萄（Grape）、苹果（Apple）和草莓（Strawberry）public interface Fruit public void plan();public void grow();public void harvest();public class Apple implements Fruit public void grow() System.out.println(苹果在生长.);public class Grape implements Fruit public void grow() System.out.println(葡萄在生长.);public class Strawberry implements Fruit public void grow() System.out.println(草莓在生长.);public class FruitGardener public static Fruit createFruit(String name)if(apple.equals(name)return new Apple();if(grape.equals(name)return new Grape();if(strawberry.equals(name)return new Strawberry();return new Apple();public class Test public static void main(String args) FruitGardener.createFruit(apple).plan();FruitGardener.createFruit(grape).grow();FruitGardener.createFruit(strawberry).grow();随着业务的扩大，农场生产的果品种类越来越多，按照原有的模式，由一个农场生产所有种类的水果，导致任务过重、判断过多，逻辑过于复杂，容易出错，难于管理，牵一发而动全身，增加新品种困难，需要改进设计模式，适应于新的情况。工厂方法模式将农场分为若干种：苹果农场负责生产苹果、草莓农场负责生产草莓、葡萄农场负责生产葡萄public interface Fruit /抽象的产品public void grow();public interface FruitFactoy /抽象的工厂public Fruit createFruit();public class Apple implements Fruit /具体的产品public void grow() System.out.println(苹果在生长.);public class Grape implements Fruit /具体的产品public void grow() System.out.println(葡萄在生长.);public class Strawberry implements Fruit /具体的产品public void grow() System.out.println(草莓在生长.);public class AppleFactory implements FruitFactoy /具体的工厂public Fruit createFruit() return new Apple();public class GrapeFactory implements FruitFactoy /具体的工厂public Fruit createFruit() return new Grape();public class StrawberryFactory implements FruitFactoy /具体的工厂public Fruit createFruit() return new Strawberry();public class Test public static void main(String args) new AppleFactory().createFruit().grow();new GrapeFactory().createFruit().grow();new StrawberryFactory().createFruit().grow();随着市场和企业定位变化，决定只生产苹果、葡萄和草莓等少数果品，但每一果品呈系列化，如：普通水果、绿色水果等等，原设计模式不能很好地适应这种需要，需要改进设计模式。抽象工厂模式农场分为两种：普通农场生产各种普通水果，绿色农场生产各种绿色水果。public interface Fruit /抽象的水果产品public void grow();public interface FruitFactoy /抽象的工厂类public Fruit createApple();/生产苹果public Fruit createGrape();/生产葡萄public Fruit createStrawberry();/生产草莓public class Apple implements Fruit /具体的产品public void grow() System.out.println(苹果在生长.);public class Grape implements Fruit /具体的产品public void grow() System.out.println(葡萄在生长.);public class Strawberry implements Fruit /具体的产品public void grow() System.out.println(草莓在生长.);public class GreenApple implements Fruit /具体的产品public void grow() System.out.println(绿色苹果在生长.);public class GreenGrape implements Fruit /具体的产品public void grow() System.out.println(绿色葡萄在生长.);public class GreenStrawberry implements Fruit /具体的产品public void grow() System.out.println(绿色草莓在生长.);public class GeneralFruitFactory implements FruitFactory/具体的工厂-普通农场public class Test public static void main(String args) FruitFactory factory=null;factory=new GreenFruitFactory();factory.createApple().grow();factory.createGrape().grow();factory.createStrawberry().grow();factory=new GeneralFruitFactory();factory.createApple().grow();factory.createGrape().grow();factory.createStrawberry().grow();public Fruit createApple() return new Apple();public Fruit createGrape() return new Grape();public Fruit createStrawberry() return new Strawberry();public class GreenFruitFactory implements FruitFactory/具体的工厂-绿色农场public Fruit createApple() return new GreenApple();public Fruit createGrape() return new GreenGrape();public Fruit createStrawberry() return new GreenStrawberry();public class Test public static void main(String args) FruitFactory factory=null;factory=new GreenFruitFactory();factory.createApple().grow();factory.createGrape().grow();factory.createStrawberry().grow();factory=new GeneralFruitFactory();factory.createApple().grow();factory.createGrape().grow();factory.createStrawberry().grow();单例模式饿汉式public class Apple implements Fruit private static Apple instance=new Apple();private Apple()public static Apple getInstance()return instance;public void grow() System.out.println(苹果在生长.);懒汉式public class Grape implements Fruit private static Grape instance;private Grape()public synchronized static Grape getInstance()if(instance=null)instance=new Grape();return instance;public void grow() System.out.println(葡萄在生长.);优化后的懒汉式public class Strawberry implements Fruit private static class StrawberrySingletonprivate static Strawberry instance=new Strawberry();public static Strawberry getInstance()return StrawberrySingleton.instance;private Strawberry()public void grow() System.out.println(草莓在生长.);登记式public class Appleprivate static final Map map=new HashMap();public static Apple getInstance(String appleClassName) throws Exceptionif(appleClassName=null)appleClassName=Apple.class.getName();Apple instance=map.get(appleClassName);if(instance=null)instance=(Apple) Class.forName(appleClassName).newInstance();map.put(appleClassName, instance);return instance;public static Apple getInstance()try return Apple.getInstance(null); catch (Exception e) / TODO Auto-generated catch blocke.printStackTrace();return null;protected Apple()public void grow() System.out.println(苹果在生长.)