c语言else如何返回上一步,if--else语句，再else的情况下怎么返回重新判断?

if--else语句，再else的情况下怎么返回重新判断?0

import java.util.Scanner;

public class LianXi05 {

public static void main(String[] args) {

System.out.print("请输入消费金额:");

Scanner input = new Scanner(System.in);

double money = 0;

String f = "未达到换购最低消费金额";

a: if (input.hasNextDouble()==true) {

money = input.nextDouble();

if (money >= 50) {

System.out.println("是否参加优惠换购活动:");

String a = "百事可乐饮料一瓶", b = "500ml可乐一瓶", c = "5公斤面粉", d = "欧苏泊尔炒菜锅", e = "莱雅爽肤水一瓶", g = "未换购商品";

System.out.println("1:满50元，加2元换购" + a);

System.out.println("2:满100元，加3元换购" + b);

System.out.println("3:满100元，加10元换购" + c);

System.out.println("4:满200元，加20元换购" + d);

System.out.println("5:满200元，加20元换购" + e);

System.out.println("0:不换购");

System.out.print("请选择:");

int xuanZhe = input.nextInt();

switch (xuanZhe) {

case 1:

money += 2;

f = a;

break;

case 2:

money += 3;

f = b;

break;

case 3:

money += 10;

f = c;

break;

case 4:

money += 10;

f = d;

break;

case 5:

money += 20;

f = e;

break;

case 0:

f = g;

break;

}

}

System.out.println("本次消费:" + money + "￥");

System.out.println("成功换购:" + f);

} else {

System.out.println("您的输入有误");

//怎么在此处返回标记 a:重新运行

}

}

}