策略设计模式以及其应用（消除if-else）

//策略接口
public interface FlyStrategy {
    void fly();
}

/**
 * 策略A
 */
public class FlyStrategyA implements FlyStrategy {
    @Override
    public void fly() {
        System.out.println("飞的很好");
    }
}

/**
 * 策略B
 */
public class FlyStrategyB implements FlyStrategy {
    @Override
    public void fly() {
        System.out.println("飞的一般");
    }
}

/**
 * 策略C
 */
public class FlyStrategyC implements FlyStrategy {
    @Override
    public void fly() {
        System.out.println("飞的很差");
    }
}

//鸭子
public class Duck {
	//聚合方式将鸭子的飞行技术添加进来
    private FlyStrategy flyStrategy;
    public Duck(FlyStrategy flyStrategy) {
        this.flyStrategy = flyStrategy;
    }
    public void fly(){
        flyStrategy.fly();
    }
	//通过set方法添加和改变鸭子的飞行技术
    public void setFlyStrategy(FlyStrategy flyStrategy) {
        this.flyStrategy = flyStrategy;
    }
}
//应用
public class Client {
    public static void main(String[] args) {
        //创建飞的好的鸭子
        Duck duck = new Duck(new FlyStrategyA());
        duck.fly();
        //创建飞的一般的鸭子
        Duck duck2 = new Duck(new FlyStrategyB());
        duck2.fly();
        //修改duck2鸭子为飞的不好的鸭子
        duck2.setFlyStrategy(new FlyStrategyC());
        duck2.fly();
    }
}

//策略抽象类
public interface Strategy {
    //抽象动作
    void process();
    //类型
    String getType();
}

//策略A
public class StrategyA implements Strategy{
    @Override
    public void process() {
        System.out.println("运行策略A");
    }
    @Override
    public String getType() {
        return "A";
    }
}

//策略B
public class StrategyB implements Strategy{
    @Override
    public void process() {
        System.out.println("运行策略B");
    }
    @Override
    public String getType() {
        return "B";
    }
}

//策略工厂，单例模式
public class StrategyFactory {
    private final static Map<String,Strategy> strategyMap = new HashMap<>();
    static {
        strategyMap.put("A",new StrategyA());
        strategyMap.put("B",new StrategyB());
    }
    public static Strategy createStrategy(String type){
        return strategyMap.get(type);
    }
}

public class Client {
    public static void main(String[] args) {
        String type = "A";
        StrategyFactory.createStrategy(type);
    }
}