软件设计之适配器模式

类模式

我们知道插座的电压为交流电220V，而日常电器使用的是直流电且电压会较小，比如手机充电会通过插头适配器达到额定的输入电流。下面我们实现这个案例：将220V电压转化为5V的电压。

package Adapter.Class;

public class Adapter extends Power220V implements Power5V {
    @Override
    public int output5V() {
        int input = output220V();
        int output = input/44;
        return output;
    }
}

package Adapter.Class;

public class Client {
    public static void main(String[] args) {
        Phone phone = new HuaWei();
        phone.charging(new Adapter());
    }
}

package Adapter.Class;

public class HuaWei implements Phone{
    @Override
    public void charging(Adapter adapter) {
        System.out.println("华为手机适配电压5伏");
        if(adapter.output5V()==5) System.out.println("华为手机充电成功");
        else System.out.println("华为手机充电不成功");
    }
}

package Adapter.Class;

public interface Phone {
    public void charging(Adapter adapter);
}

package Adapter.Class;

public interface Power5V {
    public int output5V();
}

package Adapter.Class;

public class Power220V {
    private int power = 220;
    public int output220V() {
        System.out.println("电压" + power + "伏");
        return power;
    }
}

这种模式被称作类模式，可以看到Adapter继承了Adaptee(要适配者）并且实现了Target(要适配者）。对于一对一的适配还有一种模式叫对象模式，在这种模式下，Adaptee会作为Adapter的成员属性而不是让Adapter去继承Adaptee。

对象模式

package Adapter.Object;

public class Adapter implements Power5V {
    Power220V power220V;

    public Adapter() {

    }

    public Adapter(Power220V power220V) {
        this.power220V = power220V;
    }

    @Override
    public int output5V() {
        int input = power220V.output220V();
        int output = input/44;
        return output;
    }
}

package Adapter.Object;

public class Client {
    public static void main(String[] args) {
        Phone phone = new HuaWei();
        phone.charging(new Adapter(new Power220V()));
    }
}

双向模式

上面的案例介绍了一对一的适配，还有一种适配是双向的。下面用一个案例介绍：实现猫学狗叫和狗学猫抓老鼠。

package Adapter.BothWay;

public class Adapter implements CatImpl,DogImpl{
    private CatImpl cat;
    private DogImpl dog;

    public CatImpl getCat() {
        return cat;
    }

    public void setCat(CatImpl cat) {
        this.cat = cat;
    }

    public DogImpl getDog() {
        return dog;
    }

    public void setDog(DogImpl dog) {
        this.dog = dog;
    }

    @Override
    public void catchMice() {
        System.out.print("狗学");
        cat.catchMice();
    }

    @Override
    public void cry() {
        System.out.print("猫学");
        dog.cry();
    }
}

package Adapter.BothWay;

public class Cat implements CatImpl{
    @Override
    public void catchMice() {
        System.out.println("猫抓老鼠");
    }

    @Override
    public void cry() {

    }
}

package Adapter.BothWay;

public interface CatImpl {
    public void catchMice();
    public void cry();
}

package Adapter.BothWay;

public class Dog implements DogImpl{
    @Override
    public void cry() {
        System.out.println("狗叫");
    }

    @Override
    public void catchMice() {

    }
}

package Adapter.BothWay;

public interface DogImpl {
    public void cry();
    public void catchMice();
}

package Adapter.BothWay;

public class Client {
    public static void main(String[] args) {
        Adapter adapter = new Adapter();
        CatImpl cat = new Cat();
        DogImpl dog = new Dog();
        adapter.setCat(cat);
        adapter.setDog(dog);
        cat = (CatImpl) adapter;
        cat.cry();
        dog = (DogImpl) adapter;
        dog.catchMice();
    }
}