Design Pattern: Bridge Pattern in Java

Bridge pattern is used to decouple implementation and abstraction.

NOTES

In this article, we discuss the implementation of the Bridge Pattern in Java.

See the Bridge in other languages in the “Other Code Implementations” section. Or, use the link below to check the details of the Bridge Pattern-

Check Details of Bridge Pattern

Examples

Here are some examples of Bridge pattern implementation in Java-

Example #1: UI Elements

In the example below we are implementing the Bridge pattern for a drawing UI Elements

Take a look at the class diagram.

package com.bigboxcode.designpattern.bridge.uielement;

public interface ColorSchema {
    void setColor();
}

package com.bigboxcode.designpattern.bridge.uielement;

public class Red implements ColorSchema {
    @Override
    public void setColor() {
        System.out.println("Setting proper color for Red color schema");
    }
}

package com.bigboxcode.designpattern.bridge.uielement;

public class Green implements ColorSchema {
    @Override
    public void setColor() {
        System.out.println("Setting proper color for Green color schema");
    }
}

package com.bigboxcode.designpattern.bridge.uielement;

public class Blue implements ColorSchema {
    @Override
    public void setColor() {
        System.out.println("Setting proper color for Blue color schema");
    }
}

UI Element Abstract Class

package com.bigboxcode.designpattern.bridge.uielement;

public abstract class UIElement {

    protected ColorSchema colorSchema;

    public UIElement(ColorSchema colorSchema) {
        this.colorSchema = colorSchema;
    }

    public abstract void printElement();
}

package com.bigboxcode.designpattern.bridge.uielement;

public class Button extends UIElement{

    public Button(ColorSchema colorSchema) {
        super(colorSchema);
    }

    @Override
    public void printElement() {
        // Write code for printing element
        System.out.println("Printing Button");

        // Set color schema
        colorSchema.setColor();
    }
}

package com.bigboxcode.designpattern.bridge.uielement;

public class Input extends UIElement{

    public Input(ColorSchema colorSchema) {
        super(colorSchema);
    }

    @Override
    public void printElement() {
        // Write code for printing element
        System.out.println("Printing Input");

        // Set color schema
        colorSchema.setColor();
    }
}

package com.bigboxcode.designpattern.bridge.uielement;

public class Table extends UIElement{

    public Table(ColorSchema colorSchema) {
        super(colorSchema);
    }

    @Override
    public void printElement() {
        // Write code for printing table element
        System.out.println("Printing Table");

        // Set color schema
        colorSchema.setColor();
    }
}

Demo

package com.bigboxcode.designpattern.bridge.uielement;

public class Demo {
    public static void main(String args[]) {
        // Print a Red table
        UIElement table = new Table(new Red());
        table.printElement();

        // Separator for clear view of demo result
        System.out.println("n------------------------------n");

        // Print a Green Input box
        UIElement input = new Input(new Green());
        input.printElement();

        // Separator for clear view of demo result
        System.out.println("n------------------------------n");

        // Print a Blue Button
        UIElement button = new Button(new Blue());
        button.printElement();

        // Separator for clear view of demo result
        System.out.println("n------------------------------n");

        // Print a Red Button
        UIElement button2 = new Button(new Red());
        button2.printElement();
    }
}

Output

The output of the demo above will be like below.

Printing Table
Setting proper color for Red color schema

------------------------------

Printing Input
Setting proper color for Green color schema

------------------------------

Printing Button
Setting proper color for Blue color schema

------------------------------

Printing Button
Setting proper color for Red color schema

Example #2: Transport Seat

In this example, we are going to demonstrate different types of seat selection in multiple types of transport.

Let’s take a look at the class diagram first.

package com.bigboxcode.designpattern.bridge.transport;

public interface Seat {

    void selectSeat();
}

package com.bigboxcode.designpattern.bridge.transport;

public class BusinessClassSeat implements Seat {
    @Override
    public void selectSeat() {
        System.out.println("Select an Business class seat");
    }
}

package com.bigboxcode.designpattern.bridge.transport;

public class EconomyClassSeat implements Seat{
    @Override
    public void selectSeat() {
        System.out.println("Select an Economy class seat");
    }
}

package com.bigboxcode.designpattern.bridge.transport;

public abstract class Transport {

    protected Seat seat;

    public Transport(Seat seat) {
        this.seat = seat;
    }

    public abstract void selectTransport();
}

package com.bigboxcode.designpattern.bridge.transport;

public class Plane extends Transport {

    public Plane(Seat seat) {
        super(seat);
    }

    @Override
    public void selectTransport() {
        // Write code to select transport
        System.out.println("Plane selected for transport");

        // Select seat
        seat.selectSeat();
    }
}

package com.bigboxcode.designpattern.bridge.transport;

public class Train extends Transport {

    public Train(Seat seat) {
        super(seat);
    }

    @Override
    public void selectTransport() {
        // Write code to select transport
        System.out.println("Train selected for transport");

        // Select seat
        seat.selectSeat();
    }
}

Demo

package com.bigboxcode.designpattern.bridge.transport;

public class Demo {
    public static void main(String args[]) {
        Transport plane = new Plane(new BusinessClassSeat());
        plane.selectTransport();

        // Separator for clear view of demo result
        System.out.println("n------------------------------n");

        Transport plane2 = new Plane(new EconomyClassSeat());
        plane2.selectTransport();

        // Separator for clear view of demo result
        System.out.println("n------------------------------n");

        Transport train = new Train(new EconomyClassSeat());
        train.selectTransport();
    }
}

Output

Plane selected for transport
Select an Business class seat

------------------------------

Plane selected for transport
Select an Economy class seat

------------------------------

Train selected for transport
Select an Economy class seat