HeadFirst (seven) Adapter adapter design pattern

 

Adapter mode - Adapter

Wrap an object with an incompatible interface into a compatible object

 

 

 

 

 

Facade/Facade Mode - Facade

Wrap a bunch of objects to simplify the interface

Facade pattern is used when you need to simplify and unify a large interface or a group of complex interfaces

Facades decouple clients from a complex subsystem

To implement a facade, you need to compose subsystems into the facade, and then delegate the work to the subsystem to perform

More than one facade can be implemented for a subsystem

 

Decorator Mode - Decorator

wrapping an object to add new behaviors and responsibilities

 

 

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Adapter pattern example

Make turkey duck to be compatible with parameter types of existing interfaces

 


 
 

Duck's interface

package adapter.duck;

public interface Duck {
	public void quack();
	public void fly();
}

 

concrete duck

package adapter.duck;

public class MallardDuck implements Duck {

	@Override
	public void quack() {
		System.out.println("Quack");
	}

	@Override
	public void fly() {
		System.out.println("I'm flying");
	}

}

 

turkey interface

package adapter.turkey;

public interface Turkey {
	public void gobble();
	public void fly();
}

 

specific turkey

package adapter.turkey;

public class WildTurkey implements Turkey {

	@Override
	public void gobble() {
		System.out.println("Gobble");
	}

	@Override
	public void fly() {
		System.out.println("I'm flying a short distance");
	}

}

 

Disguise a turkey as a duck

package adapter.turkey;

import adapter.duck.Duck;

/**
 * Adapter
 * Internally disguise the turkey as a duck
 */
public class TurkeyAdapter implements Duck {
	
	//adapted
	Turkey turkey;
	
	public TurkeyAdapter(Turkey turkey) {
		this.turkey = turkey;
	}
	
	/**
	 * Delegate the combined object to complete the task
	 */
	@Override
	public void quack() {
		turkey.gobble();
	}

	@Override
	public void fly() {
		for(int i=0;i<5;i++) {
			//The turkey needs to fly 5 times in a row to reach the duck to fly once
			turkey.fly();
		}
	}

}

 

Test: Make turkey compatible with interfaces that take duck types as parameters

package test;

import adapter.duck.Duck;
import adapter.duck.MallardDuck;
import adapter.turkey.Turkey;
import adapter.turkey.TurkeyAdapter;
import adapter.turkey.WildTurkey;

public class AdapterTest {
	public static void main(String[] args) {
		
		Duck duck = new MallardDuck();
		
		Turkey turkey = new WildTurkey();
		Duck turkeyAdapter = new TurkeyAdapter(turkey);
		
		System.out.println("The Turkey says:");
		turkey.gobble();
		turkey.fly();
		
		System.out.println("\nThe Duck syas:");
		testDuck(duck);
		
		System.out.println("\nThe TurkeyAdapter syas:");
		testDuck(turkeyAdapter);//Through the adapter, let the turkey become a duck
	}

	private static void testDuck(Duck duck) {
		duck.quack();
		duck.fly();
	}
}

 

 

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Enumeration Adapter