直接上课上的例子，我们购物后需要支付，支付方式可以有多种：支付宝，微信...

└── strategy    ├── AliPay.java    ├── Order.java    ├── Payment.java    ├── PayState.java    ├── PayStrategyTest.java    ├── PayType.java    └── WechatPay.java

package com.xh.pattern.strategy;/** * Created by root on 3/15/18. */public class Order {    private String uid;    private String orderId;    private double amount;    public Order(String uid, String orderId, double amount) {        this.uid = uid;        this.orderId = orderId;        this.amount = amount;    }    //这个参数，完全可以用Payment这个接口来代替    //为什么？    //完美地解决了switch的过程，不需要在代码逻辑中写switch了    //更不需要写if    else if    public PayState pay(PayType payType) {        return payType.get().pay(this.uid, this.amount);    }}

package com.xh.pattern.strategy;/** * Created by root on 3/15/18. */public interface Payment {    public PayState pay(String uid, double amount);}

package com.xh.pattern.strategy;/** * Created by root on 3/15/18. */public enum PayType {    ALI_PAY(new AliPay()),    WECHAT_PAY(new WechatPay());    private Payment payment;    PayType(Payment payment) {        this.payment = payment;    }    public Payment get() {        return this.payment;    }}

package com.xh.pattern.strategy;/** * Created by root on 3/15/18. */public class PayState {    private int code;    private Object data;    private String msg;    public PayState(int code, String msg, Object data) {        this.code = code;        this.data = data;        this.msg = msg;    }    public String toString() {        return ("支付状态：[" + code + "]," + msg + ",交易详情：" + data);    }}

package com.xh.pattern.strategy;/** * Created by root on 3/15/18. */public class AliPay implements Payment {    @Override    public PayState pay(String uid, double amount) {        System.out.println("欢迎使用支付宝");        System.out.println("查询账户余额，开始扣款");        return new PayState(200,"支付成功",amount);    }}

package com.xh.pattern.strategy;/** * Created by root on 3/15/18. */public class WechatPay implements Payment {    @Override    public PayState pay(String uid, double amount) {        System.out.println("欢迎使用微信支付");        System.out.println("直接从微信红包扣款");        return new PayState(200, "支付成功", amount);    }}

package com.xh.pattern.strategy;/** * Created by root on 3/15/18. */public class PayStrategyTest {    public static void main(String[] args) {        //省略把商品添加到购物车，再从购物车下单        //直接从点单开始        Order order = new Order("1", "20180311001000009", 324.45);        //开始支付，选择微信支付、支付宝、银联卡、京东白条、财付通        //每个渠道它支付的具体算法是不一样的        //基本算法固定的        //这个值是在支付的时候才决定用哪个值        System.out.println(order.pay(PayType.WECHAT_PAY));    }}