设计模式：策略模式

策略模式设计原则：多用组合少用继承。

策略模式定义了不同组算法族，把不同算法族封装起来，让他们之间可以互相替换，让算法独立于使用它的客户而独立变化。运行时动态改变行为；

策略模式的优点： 算法可以自由切换； 避免使用多重条件判断；  扩展性良好

策略模式的缺点：策略类会增多；所有策略类都需要对外暴露

eg：

 

package sjms.pattern.strategy;

/**
 *
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:29
 */
public class BlackDuck extends Duck{
    @Override
    public void displayer() {
        System.out.println("我是黑鸭");
    }

    public BlackDuck(){
        flyBehavior = new FlyWithWingsBehavior();
        quackBehavior = new LowQuackBehavior();
    }


}

 

package sjms.pattern.strategy;

/**
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:25
 */
public abstract class Duck {

    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;

    public abstract void displayer();

    public void swim(){
        System.out.println("所有的鸭子都会游泳");
    }

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

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

    public void setFlyBehavior(FlyBehavior flyBehavior) {
        this.flyBehavior = flyBehavior;
    }

    public void setQuackBehavior(QuackBehavior quackBehavior) {
        this.quackBehavior = quackBehavior;
    }
}

 

package sjms.pattern.strategy;

/**
 * 飞行为
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:17
 */
public interface FlyBehavior {
    public void fly();
}


package sjms.pattern.strategy;

/**
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:42
 */
public class FlyNoWayBehavior implements FlyBehavior {
    @Override
    public void fly() {
        System.out.println("没办法飞");
    }
}


package sjms.pattern.strategy;

/**
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:41
 */
public class FlyWithWingsBehavior implements FlyBehavior{
    @Override
    public void fly() {
        System.out.println("我会用翅膀飞");
    }
}

package sjms.pattern.strategy;

/**
 *
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:44
 */
public class HighQuackBehavior implements QuackBehavior{
    @Override
    public void quack() {
        System.out.println("高声音叫");
    }
}

package sjms.pattern.strategy;

/**
 *
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:44
 */
public class LowQuackBehavior implements QuackBehavior{
    @Override
    public void quack() {
        System.out.println("低声音叫");
    }
}

package sjms.pattern.strategy;

/**
 * 叫行为
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:19
 */
public interface QuackBehavior {
    public void quack();
}

package sjms.pattern.strategy;

/**
 *
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:29
 */
public class RedDuck extends Duck{
    @Override
    public void displayer() {
        System.out.println("我是红鸭");
    }

    public RedDuck(){
        flyBehavior = new FlyNoWayBehavior();
        quackBehavior = new HighQuackBehavior();
    }


}


package sjms.pattern.strategy;

/**
 *
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:44
 */
public class ScreamQuackBehavior implements QuackBehavior{
    @Override
    public void quack() {
        System.out.println("会尖叫");
    }
}

 

package sjms.pattern.strategy;

/**
 * Description:
 * User: zhurong
 * Date: 2018-07-24  22:48
 */
public class Test {
    public static void main(String[] args) {
        //black
        Duck duck  = new BlackDuck();
        duck.displayer();
        duck.performFly();
        duck.performQuack();
        System.out.println("-------------------------");
        //red
        Duck duck2  = new RedDuck();
        duck2.displayer();
        duck2.performFly();
        duck2.performQuack();
        System.out.println("-------------------------");
        duck2.setFlyBehavior(new FlyWithWingsBehavior());
        duck2.setQuackBehavior(new ScreamQuackBehavior());
        duck2.performFly();
        duck2.performQuack();
    }
}

 

运行结果：