Bridge Pattern

Bridge = “separate abstraction and implementation so both can change independently”

• Bridge pattern:
  • TV, Radio implement Device got turnOn, turnOff method.
  • Abstract RemoteControl got abstract method togglePower and interface Device via constructor
  • Concrete class override togglePower by device.turnOff

Example

// Implementation hierarchy
interface Device {
    void turnOn();
    void turnOff();
}

class TV implements Device {
    public void turnOn() { System.out.println("TV on"); }
    public void turnOff() { System.out.println("TV off"); }
}

class Radio implements Device {
    public void turnOn() { System.out.println("Radio on"); }
    public void turnOff() { System.out.println("Radio off"); }
}

// Abstraction
abstract class RemoteControl {
    protected Device device;

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

    abstract void togglePower();
}

// Refined abstraction
class BasicRemote extends RemoteControl {
    public BasicRemote(Device device) {
        super(device);
    }

    void togglePower() {
        device.turnOn(); // bridge to implementation
    }
}

Usage

public static void main(String[] args) {
    BasicRemote remote = new BasicRemote(new TV());
    remote.tooglePower();

    remote = new BasicRemote(new Radio());
    remote.tooglePower();
}