Bridge Design Pattern

Bridge design pattern is used when there is a hierarchy in abstraction as well as in its implementations. It is used to decouple abstraction from its implementation so that both can vary independent of each other.

For example, there is a remote interface. Below is the hierarchy in this abstraction. So, you can see that there is a complete hierarchy in remote such as TVRemote, ToyCarRemote, NormalRemote etc. Whereas, there is a complete hierarchy in devices as well: TV, SmartTV, ToyCar. Now, you can see that both the hierarchies can grow independently. The relationship between the top interfaces Remote and RemoteControllable works as a bridge here.

Remote interfaces hierarchy

Remote interface

package com.sks.bridge;

public interface Remote {
	
	void turnOnDevice();
	void turnOffDevice();
}

TVRemote interface

package com.sks.bridge;

public interface TVRemote extends Remote {

	void increaseVolumeOfDevice();
	void decreaseVolumeOfDevice();
	
}

ToyCarRemote

package com.sks.bridge;

public interface ToyCarRemote extends Remote {
	
	void move();

}

Remote controlled devices hierarchy

RemoteControllable interface

package com.sks.bridge;

public interface RemoteControllable extends Remote {
	

}

abstract Device class that implements RemoteControllable interface

package com.sks.bridge;

public abstract class Device implements RemoteControllable {
	
	protected String name;

	@Override
	public void turnOnDevice() {
		System.out.println(name + " is turned on");
		
	}
	
	@Override
	public void turnOffDevice() {
		System.out.println(name + " is turned off");
		
	}

	public Device(String name) {
		super();
		this.name = name;
	}
}

Concrete class TV

package com.sks.bridge;

public class TV extends Device {
	
	public void increaseVolumeOfDevice() {
		System.out.println(this.name + "'s volume is up by one point");
	}

	public void decreaseVolumeOfDevice() {
		System.out.println(this.name + "'s volume is down by one point");
	}

	public TV(String name) {
		super(name);
	}
}

SmartTV class

package com.sks.bridge;

public class SmartTV extends TV{

	public void playYouTube() {
		System.out.println("Smart tv is playing Youtube");
	}

	public SmartTV(String name) {
		super(name);
	}
	
}

ToyCar class

package com.sks.bridge;

public class ToyCar extends Device {

	public ToyCar(String name) {
		super(name);
	}
	
	public void move() {
		System.out.println(this.name + " is moving");
	}
}

Remote implementation classes

NormalRemote class

package com.sks.bridge;

public class NormalRemote implements Remote {
	
	protected Device device;
	
	public NormalRemote(Device device) {
		this.device = device;
	}

	@Override
	public void turnOnDevice() {
		System.out.println("Normal remote is turning on " + this.device.name);
		this.device.turnOnDevice();
	}

	@Override
	public void turnOffDevice() {
		System.out.println("Normal remote is turning off " + this.device.name);
		this.device.turnOffDevice();
	}

}

TVRemoteImpl

package com.sks.bridge;

public class TVRemoteImpl extends NormalRemote implements TVRemote {
	
	private TV tv;

	public TVRemoteImpl(TV tv) {
		super(tv);
		this.tv = tv;
	}

	@Override
	public void increaseVolumeOfDevice() {
		this.tv.increaseVolumeOfDevice();
	}

	@Override
	public void decreaseVolumeOfDevice() {
		this.tv.decreaseVolumeOfDevice();
	}

}

SmartTV remote

package com.sks.bridge;

public class SmartTVRemote extends TVRemoteImpl {

	public SmartTVRemote(TV tv) {
		super(tv);
	}
	
	public void playYouTube() {
		System.out.println("Playing youtube on " + device.name);
	}	
}

ToyCarRemoteImpl class

package com.sks.bridge;

public class TVRemoteImpl extends NormalRemote implements TVRemote {
	
	private TV tv;

	public TVRemoteImpl(TV tv) {
		super(tv);
		this.tv = tv;
	}

	@Override
	public void increaseVolumeOfDevice() {
		this.tv.increaseVolumeOfDevice();
	}

	@Override
	public void decreaseVolumeOfDevice() {
		this.tv.decreaseVolumeOfDevice();
	}

}

Bridge pattern testing class

package com.sks.bridge;

public class BridgePatternTest {
	
	public static void main(String[] args) {
		
		TV tv = new TV("Sony Bravia");
		TVRemote remote = new TVRemoteImpl(tv);
		
		remote.turnOnDevice();
		remote.increaseVolumeOfDevice();
		
		SmartTV tv1 = new SmartTV("Oneplus Smart TV");
		SmartTVRemote remote1 = new SmartTVRemote(tv1);
		
		remote1.playYouTube();
		
		ToyCar toyCar = new ToyCar("Red Toy Car");
		ToyCarRemote remote2 = new ToyCarRemoteImpl(toyCar);
		remote2.turnOnDevice();
		remote2.move();
	}

}

Output :