Bridge Design Pattern in Java With Examples

Today we will look into Bridge Design Pattern in java. When we have interface hierarchies in both interfaces as well as implementations, then bridge design pattern is used to decouple the interfaces from implementation and hiding the implementation details from the client programs.

Bridge Design Pattern

Just like Adapter pattern, bridge design pattern is one of the Structural design pattern.

According to GoF bridge design pattern is:

Decouple an abstraction from its implementation so that the two can vary independently

The implementation of bridge design pattern follows the notion to prefer Composition over inheritance.

Bridge Design Pattern in Java Example

If we look into bridge design pattern with example, it will be easy to understand. Lets say we have an interface hierarchy in both interfaces and implementations like below image.

Bridge-Interface-Hierarchy

Now we will use bridge design pattern to decouple the interfaces from implementation. UML diagram for the classes and interfaces after applying bridge pattern will look like below image.

Bridge Design Pattern in Java Example

Notice the bridge between Shape and Color interfaces and use of composition in implementing the bridge pattern.

Here is the java code for Shape and Color interfaces.

Color.java

Shape.java

We have Triangle and Pentagon implementation classes as below.

Triangle.java

Pentagon.java

Here are the implementation classes for RedColor and GreenColor.

RedColor.java

GreenColor.java

Lets test our bridge pattern implementation with a test program.

BridgePatternTest.java

Output of above bridge pattern example program is:

Bridge design pattern can be used when both abstraction and implementation can have different hierarchies independently and we want to hide the implementation from the client application.

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