策略模式

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策略模式（Strategy），定义一系列的算法，把它们一个个封装起来，并且使它们可相互替换。本模式使得算法的变化可独立于使用它的客户。

package gof23;public class StrategyTest {public static void main(String[] args) {CashContext cc = null;cc = new CashContext("正常收费");System.out.println("收费为:" + cc.getResult(2000) +"元");cc = new CashContext("满300返100");System.out.println("收费为:" + cc.getResult(2000) +"元");cc = new CashContext("打8折");System.out.println("收费为:" + cc.getResult(2000) +"元");}}class CashContext {private CashSuper cs = null;public CashContext(String type) {switch(type) {case "正常收费":CashNormal cs0 = new CashNormal();cs = cs0;break;case "满300返100":CashReturn cs1 = new CashReturn(300, 100);cs= cs1;break;case "打8折":CashRebate cs2 = new CashRebate(0.8);cs = cs2;break;}}public double getResult(double money) {return cs.acceptCash(money);}}abstract class CashSuper {public abstract double acceptCash(double money);}/* * 正常收费，原价返回 */class CashNormal extends CashSuper {@Overridepublic double acceptCash(double money) {return money;}}/* * 打折收费，初始化时，需要输入折扣率，如0.8 */class CashRebate extends CashSuper {private double moneyRebate = 1d;public CashRebate(double moneyRebate) {this.moneyRebate = moneyRebate;}@Overridepublic double acceptCash(double money) {return money * moneyRebate;}}/* * 返利收费，初始化时必须输入返利条件和返利值，比如满300返100， * 则moneyCondition为300，moneyReturn为100 */class CashReturn extends CashSuper {private double moneyCondition = 0.0d;private double moneyReturn = 0.0d;public CashReturn(double moneyCondition, double moneyReturn) {this.moneyCondition = moneyCondition;this.moneyReturn = moneyReturn;}@Overridepublic double acceptCash(double money) {double result  = money;if(result > moneyCondition)result = money - Math.floor(money / moneyCondition) * moneyReturn;return result;}}

运行结果为：

收费为:2000.0元收费为:1400.0元收费为:1600.0元

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