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桥接模式

2022/11/17 设计模式

# 定义

# 桥接是一种结构型设计模式， 可将业务逻辑或一个大类拆分为不同的层次结构， 从而能独立地进行开发。

层次结构中的第一层 （通常称为抽象部分） 将包含对第二层 （实现部分） 对象的引用。 抽象部分将能将一些 （有时是绝大部分） 对自己的调用委派给实现部分的对象。 所有的实现部分都有一个通用接口， 因此它们能在抽象部分内部相互替换。

# 结构

# 伪代码

# 示例

# 设备和远程控制之间的桥接

本例展示了远程控制器及其所控制的设备的类之间的分离。

远程控制器是抽象部分， 设备则是其实现部分。 由于有通用的接口， 同一远程控制器可与不同的设备合作， 反过来也一样。

桥接模式允许在不改动另一层次代码的前提下修改已有类， 甚至创建新类。

# 1. 所有设备的通用接口: bridge.Device.java

package bridge;

public interface Device  {

    boolean isEnabled();

    void enable();

    void disable();

    int getVolume();

    void setVolume(int percent);

    int getChannel();

    void setChannel(int channel);

    void printStatus();


}
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# 2. 收音机: bridge.Radio.java

package bridge;

public class Radio implements Device {

    private boolean on = false;
    private int volume = 30;
    private int channel = 1;

    public boolean isEnabled() {
        return on;
    }

    public void enable() {
        on = true;
    }

    public void disable() {
        on = false;
    }

    public int getVolume() {
        return volume;
    }

    public void setVolume(int volume) {
        if (volume > 100) {
            this.volume = 100;
        } else if (volume < 0) {
            this.volume = 0;
        } else {
            this.volume = volume;
        }
    }

    public int getChannel() {
        return channel;
    }

    public void setChannel(int channel) {
        this.channel = channel;
    }

    public void printStatus() {
        System.out.println("------------------------------------");
        System.out.println("| I'm radio.");
        System.out.println("| I'm " + (on ? "enabled" : "disabled"));
        System.out.println("| Current volume is " + volume + "%");
        System.out.println("| Current channel is " + channel);
        System.out.println("------------------------------------\n");
    }

}
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# 3. 电视机: bridge.Tv.java

package bridge;

public class Tv implements Device {

    private boolean on = false;
    private int volume = 30;
    private int channel = 1;

    public boolean isEnabled() {
        return on;
    }

    public void enable() {
        on = true;
    }

    public void disable() {
        on = false;
    }

    public int getVolume() {
        return volume;
    }

    public void setVolume(int volume) {
        if (volume > 100) {
            this.volume = 100;
        } else if (volume < 0) {
            this.volume = 0;
        } else {
            this.volume = volume;
        }
    }

    public int getChannel() {
        return channel;
    }

    public void setChannel(int channel) {
        this.channel = channel;
    }

    public void printStatus() {
        System.out.println("------------------------------------");
        System.out.println("| I'm TV set.");
        System.out.println("| I'm " + (on ? "enabled" : "disabled"));
        System.out.println("| Current volume is " + volume + "%");
        System.out.println("| Current channel is " + channel);
        System.out.println("------------------------------------\n");
    }

}
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# 4. 所有远程控制器的通用接口: bridge.Remote.java

package bridge;

public interface Remote {

    void power();

    void volumeDown();

    void volumeUp();

    void channelDown();

    void channelUp();

}
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# 5. 基础远程控制器: bridge.BasicRemote.java

package bridge;

public class BasicRemote implements Remote {

    protected Device device;

    public BasicRemote() {}

    public BasicRemote(Device device) {
        this.device = device;
    }

    public void power() {
        System.out.println("Remote: power toggle");
        if (device.isEnabled()) {
            device.disable();
        } else {
            device.enable();
        }
    }

    public void volumeDown() {
        System.out.println("Remote: volume down");
        device.setVolume(device.getVolume() - 10);
    }

    public void volumeUp() {
        System.out.println("Remote: volume up");
        device.setVolume(device.getVolume() + 10);
    }

    public void channelDown() {
        System.out.println("Remote: channel down");
        device.setChannel(device.getChannel() - 1);
    }

    public void channelUp() {
        System.out.println("Remote: channel up");
        device.setChannel(device.getChannel() + 1);
    }

}
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# 6. 高级远程控制器: bridge.AdvancedRemote.java

package bridge;

public class AdvancedRemote extends BasicRemote {

    public AdvancedRemote(Device device) {
        super.device = device;
    }

    public void mute() {
        System.out.println("Remote: mute");
        device.setVolume(0);
    }

}
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# 7. 客户端代码: bridge.Demo.java

package bridge;

public class Demo {

    public static void main(String[] args) {
        testDevice(new Tv());
        testDevice(new Radio());
    }

    public static void testDevice(Device device) {
        System.out.println("Tests with basic remote.");
        BasicRemote basicRemote = new BasicRemote(device);
        basicRemote.power();
        device.printStatus();

        System.out.println("Tests with advanced remote.");
        AdvancedRemote advancedRemote = new AdvancedRemote(device);
        advancedRemote.power();
        advancedRemote.mute();
        device.printStatus();
    }

}
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# 8. 输出结果

Tests with basic remote.
Remote: power toggle
------------------------------------
| I'm TV set.
| I'm enabled
| Current volume is 30%
| Current channel is 1
------------------------------------

Tests with advanced remote.
Remote: power toggle
Remote: mute
------------------------------------
| I'm TV set.
| I'm disabled
| Current volume is 0%
| Current channel is 1
------------------------------------

Tests with basic remote.
Remote: power toggle
------------------------------------
| I'm radio.
| I'm enabled
| Current volume is 30%
| Current channel is 1
------------------------------------

Tests with advanced remote.
Remote: power toggle
Remote: mute
------------------------------------
| I'm radio.
| I'm disabled
| Current volume is 0%
| Current channel is 1
------------------------------------
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Last Updated: 2022/11/16 22:59:51