策略模式

/**
 * 定义一个购买球的策略类
 * @author Tim
 *
 */
public interface Ball {

    public double price(double price);
}

/**
 * 足球的购买价钱
 * @author Tim
 *
 */
public class FootBall implements Ball{

    public double price(double price) {
        return price * 0.9;
    }

}

/**
 * 篮球类
 * @author Tim
 *
 */
public class BasketBall implements Ball{

    public double price(double price) {
        return price * 0.6;
    }

}

/**
 * 定义环境类
 * @author Tim
 *
 */
public class Strategy {

    private Ball ball;

    public Strategy(Ball ball) {
        this.ball = ball;
    }
    
    public double priceBall(double price) {
        return this.ball.price(price);
    }
    
}

public class StrategyMain {

    public static void main(String[] args) {
        
        Ball ball = new FootBall();
        Strategy strategy = new Strategy(ball);
        System.err.println(strategy.priceBall(18));
    }
}