设计模式（二）策略模式(Strategy)

1.分析项目中变化部分与不变部分

2.多用组合，少用继承；用行为类组合，而不是行为的继承

案例：

第一步，把行为抽象为接口

package top.littlepage.designPattern.Strategy;

public interface FlyBehavior {
    void fly();
}

第二步，把具体行为用实体类实现

package top.littlepage.designPattern.Strategy;

public class BadFly implements FlyBehavior{

    @Override
    public void fly() {
        System.out.println("--bad fly--");
    }
    
}

package top.littlepage.designPattern.Strategy;

public class NotFly implements FlyBehavior{

    @Override
    public void fly() {
        System.out.println("--not fly--");
    }

}

package top.littlepage.designPattern.Strategy;

public class GoodFly implements FlyBehavior{

    @Override
    public void fly() {
        System.out.println("--good fly--");
    }

}

第三步，做出具体的环境进行实现该实体

package top.littlepage.designPattern.Strategy;

public class Bird {
    private String name;
    private int age;
    private GoodFly goodfly;
    private BadFly badfly;
    private NotFly notfly;
    
    public Bird() {
        name="";
        age=0;
        goodfly=new GoodFly();
        badfly=new BadFly();
        notfly=new NotFly();
    }
    public GoodFly getGoodfly() {
        return goodfly;
    }
    public void setGoodfly(GoodFly goodfly) {
        this.goodfly = goodfly;
    }
    public BadFly getBadfly() {
        return badfly;
    }
    public void setBadfly(BadFly badfly) {
        this.badfly = badfly;
    }
    public NotFly getNotfly() {
        return notfly;
    }
    public void setNotfly(NotFly notfly) {
        this.notfly = notfly;
    }
    public Bird(String name, int age) {
        this.name = name;
        this.age = age;
        goodfly=new GoodFly();
        badfly=new BadFly();
        notfly=new NotFly();
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
}

测试：

package top.littlepage.designPattern.Strategy;

public class Test {
    public static void main(String[] args) {
        Bird b=new Bird("小鸟",2);
        System.out.print(b.getName());
        b.getGoodfly().fly();
        
        System.out.print(b.getName());
        b.getBadfly().fly();
        
        System.out.print(b.getName());
        b.getNotfly().fly();
    }
}

控制台截图

策略模式(strategy)利用接口进行抽象，利用实体进行实现抽象，再做出环境进行实现具体的实体

在我们面向对象后，经常利用这种设计模式进行编程，应该是比较简单的一种模式