策略模式

// 策略模式
// 定义一个抽象类
public abstract class Strategy {
    public abstract void algorithm();
}

// 定义具体的策略
public class ConcreteStrategyA extends Strategy {
    public void algorithm() {
        System.out.println("使用策略A");
    }
}

public class ConcreteStrategyB extends Strategy {
    public void algorithm() {
        System.out.println("使用策略B");
    }
}

// 定义上下文类
public class Context {
    private Strategy strategy;

    public Context(Strategy strategy) {
        this.strategy = strategy;
    }

    public void executeAlgorithm() {
        strategy.algorithm();
    }
}

// 测试类
public class Test {
    public static void main(String[] args) {
        Context context;

        context = new Context(new ConcreteStrategyA());
        context.executeAlgorithm();

        context = new Context(new ConcreteStrategyB());
        context.executeAlgorithm();
    }
}