设计模式笔记： 1 设计模式入门，策略模式

场景：创建各种鸭子

概念：

设计原则：

1.抽取变化之处

2.对接口编程

3.多用组合少用继承

UML 图：

代码：

// FlyBehavior =====================================================
public interface FlyBehavior { public void fly(); }

public class FlyNoWay implements FlyBehavior {
    @Override
    public void fly() { System.out.println("I cannot fly");}
}

public class FlyWithWings implements FlyBehavior {
    @Override
    public void fly() { System.out.println("I'm flying !!"); }
}

// QuackBehavior =====================================================
public interface QuackBehavior { public void quack(); }

public class MuteQuack implements QuackBehavior {
    @Override
    public void quack() { System.out.println("quack.MuteQuack"); }
}

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

public class Squeak implements QuackBehavior {
    @Override
    public void quack() { System.out.println("quack.Squeak"); }
}

// Duck ==================================================================
public abstract class Duck {
    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;

    public Duck() {}

    public abstract void display();

    public void performFly() { flyBehavior.fly();}

    public void performQuack() { quackBehavior.quack();}

    // 动态设定行为
    public void setFlyBehavior(FlyBehavior fb) { flyBehavior = fb; }

    public void setQuackBehavior(QuackBehavior qb) { quackBehavior = qb; }

    public void swim() {
        // 所有的鸭子漂浮，甚至诱饵鸭！
        System.out.println("all ducks float, even decoys!");
    }
}

public class MallardDuck extends Duck {

    public MallardDuck() {
        quackBehavior = new Quack();
        flyBehavior = new FlyWithWings();
    }

    @Override
    public void display() { System.out.println("I'm a real mallard duck");}
}

// test ==================================================================
public class MiniDuckSimulator {
    public static void main(String[] args) {
        Duck mallard = new MallardDuck();

        mallard.performQuack();
        mallard.performFly();

        // 动态设定行为
        mallard.setFlyBehavior(new FlyNoWay());
        mallard.performFly();
    }
}
// 输出：
// Quack
// I'm flying !!
// I cannot fly

有价值的问答：

全文完。