Head First Design Patterns Chapter 7 (Adapter Pattern and Facade Pattern) Notes

Adapter pattern: Convert the interface of a class into another interface that the client expects. Adapters allow classes with incompatible interfaces to work together.

Understanding: In fact, the composition, object adapter is used, an object is passed in an object, and the method of the current object calls the method of the incoming object. . . .

example:

1. Duck, Turkey interface

package adapter.ducks;

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

package adapter.ducks;

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

2. Implementation of Duck and Turkey interfaces

package adapter.ducks;

public class MallardDuck implements Duck {
	public void quack() {
		System.out.println("Quack");
	}
 
	public void fly() {
		System.out.println("I'm flying");
	}
}

package adapter.ducks;

public class WildTurkey implements Turkey {
	public void gobble() {
		System.out.println("Gobble gobble");
	}
 
	public void fly() {
		System.out.println("I'm flying a short distance");
	}
}

3. Two adapters DuckAdapter and TurkeyAdapter classes

package adapter.ducks;
import java.util.Random;

public class DuckAdapter implements Turkey {
	Duck duck;
	Random rand;
 
	public DuckAdapter(Duck duck) {
		this.duck = duck;
		rand = new Random();
	}
    
	public void gobble() {
		duck.quack();
	}
  
	public void fly() {
		if (rand.nextInt(5)  == 0) {
		     duck.fly();
		}
	}
}

package adapter.ducks;

public class TurkeyAdapter implements Duck {
	Turkey turkey;
 
	public TurkeyAdapter(Turkey turkey) {
		this.turkey = turkey;
	}
    
	public void quack() {
		turkey.gobble();
	}
  
	public void fly() {
		for(int i=0; i < 5; i++) {
			turkey.fly();
		}
	}
}

4. Test class

package adapter.ducks;

public class TurkeyTestDrive {
	public static void main(String[] args) {
		MallardDuck duck = new MallardDuck();
		Turkey duckAdapter = new DuckAdapter(duck);
 
		for(int i=0;i<10;i++) {
			System.out.println("The DuckAdapter says...");
			duckAdapter.gobble();
			duckAdapter.fly();
		}
	}
}

package adapter.ducks;

public class DuckTestDrive {
	public static void main(String[] args) {
		MallardDuck duck = new MallardDuck();

		WildTurkey turkey = new WildTurkey ();
		Duck turkeyAdapter = new TurkeyAdapter(turkey);

		System.out.println("The Turkey says...");
		turkey.gobble();
		turkey.fly();

		System.out.println("\nThe Duck says...");
		testDuck(duck);

		System.out.println("\nThe TurkeyAdapter says...");
		testDuck(turkeyAdapter);
	}

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