java接口作用（2）

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用java接口实现工厂模式如下：

interface Service{
    void method1();
    void method2();
}

interface ServiceFactory{
    Service getService();
}

class Implementation1 implements Service{
    Implementation1(){};
    public void method1(){System.out.println("Implemention1 method1");}
    public void method2(){System.out.println("Implemention1 method2");}
}

class Implementation2 implements Service{
    Implementation2(){}
    public void method1(){System.out.println("Implementation2 method1");}
    public void method2(){System.out.println("Implementation2 method2");}
}

class Implementation1ServiceFactory implements ServiceFactory{
    public Service getService(){
        return new Implementation1();
    }
}

class Implementation2ServiceFactory implements ServiceFactory{
    public Service getService(){
        return new Implementation2();
    }
}

public class TopCoder{
    public static void main(String[] args){
        serviceConsumer(new Implementation1ServiceFactory());
        serviceConsumer(new Implementation2ServiceFactory());
    }

    public static void serviceConsumer(ServiceFactory sf){
        Service s=sf.getService();
        s.method1();
        s.method2();
    }
}

该实现有一个小小的缺憾，那就是Implementation1 和 Implementation2的构造函数都是public。下面用Java的内部类实现工厂模式，可以弥补这个缺憾

interface Service{
    void method1();
    void method2();
}

interface ServiceFactory{
    Service getService();
}

class Implementation1 implements Service{
    Implementation1(){};
    public void method1(){System.out.println("Implemention1 method1");}
    public void method2(){System.out.println("Implemention1 method2");}

    public static ServiceFactory factory=new ServiceFactory(){
        public Service getService(){
            return new Implementation1();
        }
    };
}

class Implementation2 implements Service{
    Implementation2(){}
    public void method1(){System.out.println("Implementation2 method1");}
    public void method2(){System.out.println("Implementation2 method2");}

    public static ServiceFactory factory=new ServiceFactory(){
        public Service getService(){
            return new Implementation2();
        }
    };
}

public class TopCoder{
    public static void main(String[] args){
        serviceConsumer(Implementation1.factory);
        serviceConsumer(Implementation2.factory);
    }

    public static void serviceConsumer(ServiceFactory sf){
        Service s=sf.getService();
        s.method1();
        s.method2();
    }
}