/**
 * 策略接口
 *
 * @author Promsing(張有博)
 * @version 1.0.0
 * @since 2022/9/6 - 18:13
 */
public interface Strategy {

    //頂層策略接口
    void Strategy();

}

實(shí)現(xiàn)類-三個(gè)

/**
 * 策略實(shí)現(xiàn)A
 *
 * @author Promsing(張有博)
 * @version 1.0.0
 * @since 2022/9/6 - 18:14
 */
public class ConcreteStrategyA  implements Strategy{

    @Override
    public void Strategy() {
        System.out.println("算法A實(shí)現(xiàn)");
    }
}

/**
 * 策略實(shí)現(xiàn)B
 *
 * @author Promsing(張有博)
 * @version 1.0.0
 * @since 2022/9/6 - 18:14
 */
public class ConcreteStrategyB implements Strategy {
    @Override
    public void Strategy() {
        System.out.println("算法B實(shí)現(xiàn)");
    }
}


/**
 * 策略實(shí)現(xiàn)C
 *
 * @author Promsing(張有博)
 * @version 1.0.0
 * @since 2022/9/6 - 18:14
 */
public class ConcreteStrategyC implements Strategy{

    @Override
    public void Strategy() {
        System.out.println("算法C實(shí)現(xiàn)");
    }
}

Context類

/**
 * 策略配置類，維護(hù)一個(gè)Strategy的引用
 *
 * @author Promsing(張有博)
 * @version 1.0.0
 * @since 2022/9/6 - 18:15
 */
public class Context {

    //聲明策略接口
    private Strategy strategy;

    //使用聚合的方式
    public Context(Strategy strategy) {
        this.strategy = strategy;
    }
    
    //提供set方法，支持運(yùn)行時(shí)改變算法
    public void setStrategy(Strategy strategy) {
        this.strategy = strategy;
    }

    //根據(jù)具體的策略對象，調(diào)用其算法的方法
    public void ContextStrategy(){
        strategy.Strategy();
    }
   
}

Main方法

/**
 * 策略模式啟動類
 *
 * @author Promsing(張有博)
 * @version 1.0.0
 * @since 2022/9/6 - 18:19
 */
public class Main
{
    //TODO:代碼可以優(yōu)化，new的具體算法，可以放到配置文件中。
    //運(yùn)行時(shí)讀取配置文件
    public static void main(String[] args) {
        Context context;
        //new 一個(gè)context對象
        context=new Context(new ConcreteStrategyA());
        context.ContextStrategy();
        
        //運(yùn)行時(shí)改變策略
        context.setStrategy(new ConcreteStrategyB());
        context.ContextStrategy();

        context.setStrategy(new ConcreteStrategyC());
        context.ContextStrategy();
    }

}

拓展

JDK源碼

Comparator接口是一個(gè)常用的比較器，其中compare()就是一個(gè)策略模式的抽象體現(xiàn)

public static void main2(String[] args) {
        Integer[] ints={1,3,8,2,4,9,0};

        Comparator<Integer> comparator = new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                if (o1 > o2) {
                    return 1;
                }
                return -1;
            }
        };

        Arrays.sort(ints,comparator);

        System.out.println(Arrays.toString(ints));

 }