A detailed introduction to the Java implementation strategy (Strategy) pattern

Strategy pattern: Behavioral pattern

Encapsulates the same behavior and different processing algorithms respectively. Make them interchangeable

1. Define a supertype interface and behavior method

2. Define different implementation classes, Different algorithms to achieve this behavior

##

/**
 * 策略模式：针对同一命令(或行为),不同的策略做不同的动作
 *  商品促销
 *  本类为：收取现金的类
 *  
 *  @author stone
 */
public interface ICashSuper {
	 double acceptCash(double money);
}

/**
 * 正常收取现金
 * @author stone
 *
 */
public class CashNormal implements ICashSuper {

	@Override
	public double acceptCash(double money) {
		return money;
	}

}

/**
 * 打折收取现金 
 * @author stone
 *
 */
public class CashRebate implements ICashSuper {
	private double rebate; //折扣
	public CashRebate (double rebate) {
		this.rebate = rebate;
	}

	@Override
	public double acceptCash(double money) {
		return new BigDecimal(money * rebate / 10).setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();
	}
	
	
}

/**
 * 让利返现  收取现金
 * @author stone
 *
 */
public class CashReturn implements ICashSuper {
	private double moneyCondition; //返现底限金额
	private double returnMoney; //返还金额
	public CashReturn(double moneyCondition, double returnMoney) {
		this.moneyCondition = moneyCondition;
		this.returnMoney = returnMoney;
	}

	@Override
	public double acceptCash(double money) {//多重返利
		if (money >= moneyCondition) {
			return money - Math.floor(money / moneyCondition) * returnMoney;
		} else {
			return money;
		}
	}
	
	
}

/**
 * 根据传递的的策略类，执行相应的行为
 * @author stone
 *
 */
public class CashContext {
	private ICashSuper casher;
	
	public CashContext() {
		
	}
	
	public CashContext(ICashSuper casher) {
		this.casher = casher;
	}
	
	public void setCasher(ICashSuper casher) {
		this.casher = casher;
	}
	
	//根据具体的策略对象，调用它的算法行为
	public double acceptCash(double money) {
		return this.casher.acceptCash(money);
	}
	
}

/*
 * 策略(Strategy)模式 关注：行为的选择
 * 封装了一系列策略对象，用户来选择使用哪种策略对象
 * 与简单工厂的区别：
 * 		策略模式，传入策略对象给Context，由Context封装策略对象的方法调用，对外公开Context的方法接口
 * 		简单工厂模式，传入一个简单参数，创建对象，然后调用出厂对象的方法
 * 与装饰模式的区别：
 * 		很明显，Context无需实现(implements)业务接口,不需要增强已有的策略对象的功能
 * 策略模式多用在算法决策系统中, 比如工资结算
 */
public class Test {
	public static void main(String[] args) {
		double money = 998; //原价
		CashContext cashContext = new CashContext(new CashNormal());
		System.out.println("原价：" + cashContext.acceptCash(money)); //通常  策略
		
		cashContext.setCasher(new CashRebate(8.5));
		System.out.println("打85折：" + cashContext.acceptCash(money)); //折扣   策略   85折
		
		cashContext.setCasher(new CashReturn(300, 50));
		System.out.println("满300 返50：" + cashContext.acceptCash(money)); //返现  策略    满300 返50
		
	}
}

Print

原价：998.0
打85折：848.3
满300 返50：848.0

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