Definition

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

UML class diagram

Participants

• Abstraction
  • defines the abstraction's interface.
  • maintains a reference to an object of type Implementor.
• RefinedAbstraction
  • extends the interface defined by Abstraction.
• Implementor
  • defines the interface for implementation classes.
• ConcreteImplementor
  • implements the Implementor interface and defines its concrete implementation.

Sample code in Java

package com.hong.bridge;

interface Implementor
{
    public void operation();
}

class ConcreteImplementorA implements Implementor
{

    @Override
    public void operation() {
        System.out.println("Calls Implementor's operation from ConcreteImplementorA");
    }
}

class ConcreteImplementorB implements Implementor
{
    @Override
    public void operation() {
        System.out.println("Calls Implementor's operation from ConcreteImplementorB");
    }
}

interface Abstraction
{
    public void setImplementor(Implementor implementor);
    public void operation();
}

class RefinedAbstraction implements Abstraction
{   
    private Implementor implementor;

    public RefinedAbstraction(){}
    
    @Override
    public void setImplementor(Implementor implementor) {
        this.implementor = implementor;
    } 

    @Override
    public void operation() {
        if(null != implementor)
            implementor.operation();
    }
}

public class Bridge_structure {
    
        public static void main(String[] args)
        {
            Abstraction rf_abs = new RefinedAbstraction(); 
    
            rf_abs.setImplementor(new ConcreteImplementorA());
            rf_abs.operation(); 
            
            rf_abs.setImplementor(new ConcreteImplementorB());
            rf_abs.operation(); 
            
        }
}