Java适配器模式的两种分类以及具体应用场景

1、类适配器模式

实现方式：定义一个适配器类来实现当前系统的业务接口，同时又继承现有组件库中已经存在的组件。

public class HelloWorld {
    public static void main(String[] args) {
        Computer computer = new Computer();
        SDCard sdCard = new SDCardImpl();
        System.out.println(computer.readSD(sdCard));
 
        System.out.println("------------");
 
        SDAdapterTF adapter = new SDAdapterTF();
        System.out.println(computer.readSD(adapter));
    }
}
 
// SD卡的接口
interface SDCard {
    // 读取SD卡功能
    String readSD();
 
    // 写入SD卡功能
    void writeSD(String msg);
}
 
// SD卡实现类
class SDCardImpl implements SDCard {
    @Override
    public String readSD() {
        String msg = "sd card read a msg: hello sd card";
        return msg;
    }
 
    @Override
    public void writeSD(String msg) {
        System.out.println("sd card write msg: " + msg);
    }
}
 
// 电脑类
class Computer {
    public String readSD(SDCard sdCard) {
        if (sdCard == null) {
            throw new NullPointerException("sd card null");
        }
        return sdCard.readSD();
    }
}
 
// TF卡接口
interface TFCard {
    // 读取TF卡功能
    String readTF();
 
    // 写入TF卡功能
    void writeTF(String msg);
}
 
// TF卡实现类
class TFCardImpl implements TFCard {
    @Override
    public String readTF() {
        String msg = "sd card read a msg: hello tf card";
        return msg;
    }
 
    @Override
    public void writeTF(String msg) {
        System.out.println("tf card write msg: " + msg);
    }
}
 
// 定义适配器类（SD兼容TF）
class SDAdapterTF extends TFCardImpl implements SDCard {
    @Override
    public String readSD() {
        System.out.println("adapter read tf card ");
        return readTF();
    }
 
    @Override
    public void writeSD(String msg) {
        System.out.println("adapter write tf card");
        writeTF(msg);
    }
}

2、对象适配器模式

实现方式：对象适配器模式可采用将现有组件库中已经实现的组件引入适配器中，该类同时实现当前系统的业务接口。

public class HelloWorld {
    public static void main(String[] args) {
        Computer computer = new Computer();
        SDCard sdCard = new SDCardImpl();
        System.out.println(computer.readSD(sdCard));
 
        System.out.println("------------");
        
        TFCard tfCard = new TFCardImpl();
        SDAdapterTF adapter = new SDAdapterTF(tfCard);
        System.out.println(computer.readSD(adapter));
    }
}
 
// SD卡的接口
interface SDCard {
    // 读取SD卡功能
    String readSD();
 
    // 写入SD卡功能
    void writeSD(String msg);
}
 
// SD卡实现类
class SDCardImpl implements SDCard {
    @Override
    public String readSD() {
        String msg = "sd card read a msg: hello sd card";
        return msg;
    }
 
    @Override
    public void writeSD(String msg) {
        System.out.println("sd card write msg: " + msg);
    }
}
 
// 电脑类
class Computer {
    public String readSD(SDCard sdCard) {
        if (sdCard == null) {
            throw new NullPointerException("sd card null");
        }
        return sdCard.readSD();
    }
}
 
// TF卡接口
interface TFCard {
    // 读取TF卡功能
    String readTF();
 
    // 写入TF卡功能
    void writeTF(String msg);
}
 
// TF卡实现类
class TFCardImpl implements TFCard {
    @Override
    public String readTF() {
        String msg = "sd card read a msg: hello tf card";
        return msg;
    }
 
    @Override
    public void writeTF(String msg) {
        System.out.println("tf card write msg: " + msg);
    }
}
 
// 定义适配器类（SD兼容TF）
class SDAdapterTF implements SDCard {
    private TFCard tfCard;
 
    public SDAdapterTF(TFCard tfCard) {
        this.tfCard = tfCard;
    }
 
    @Override
    public String readSD() {
        System.out.println("adapter read tf card ");
        return tfCard.readTF();
    }
 
    @Override
    public void writeSD(String msg) {
        System.out.println("adapter write tf card");
        tfCard.writeTF(msg);
    }
}

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