Java编程：循环结构实战-计算偶数和与购物结算-优快云博客

这篇博客介绍了两个Java编程实战练习，分别是使用循环计算100以内偶数的和，以及实现一个购物结算系统，包括商品选择、数量输入、折扣计算和实付金额验证。

练习1：计算100以内（包括100）的偶数之和

package cn.jbit.loops1;

public class EvenSum {

   /*
   * 计算100以内偶数之和
   */
   public static void main(String[] args) {
       int sum = 0;   //当前之和
       int num = 2;   //加数
       while(num <= 100){
           sum = sum + num;   //累加
           num = num + 2;
       }
       System.out.println("100以内的偶数之和为：" + sum);
   }
}
练习3：升级购物结算

package cn.jbit.loops1;

import java.util.Scanner;

public class Pay {

   /*
   * 购物结算
   */
   public static void main(String[] args) {
       String name = "";       //商品名称
       double price = 0.0;       //商品价格
       int goodsNo = 0;       //商品编号
       int amount = 0;           //购买数量
       double discount = 0.8;   //折扣比例
       double total = 0.0;       //商品总价
       double payment = 0.0;   //实付金额

       //商品清单
       System.out.println("*******************************************");
       System.out.println("请选择购买的商品编号：");
       System.out.println("1.T 恤 2.网球鞋 3.网球拍");
       System.out.println("*******************************************");

       Scanner input = new Scanner(System.in);
       String answer = "y";   //标识是否继续

       while("y".equals(answer)){
           System.out.print("\n请输入商品编号：");
           goodsNo = input.nextInt();
           switch(goodsNo){
           case 1:
               name = "T 恤";
               price = 245;
               break;
           case 2:
               name = "网球鞋";
               price = 570;
               break;
           case 3:
               name = "网球拍";
               price = 320;
               break;
           }
           System.out.print("请输入购买数量：");
           amount = input.nextInt();
           System.out.println(name+ "￥" + price +"\t数量 " + amount
                   + "\t合计￥" + price*amount);
           total += price*amount;
           System.out.print("是否继续（y/n）");
           answer = input.next();
       }
       System.out.println("\n折扣：" + discount);
       System.out.println("应付金额：" +total*discount);
       System.out.print("实付金额：");
       payment = input.nextDouble();
       while(payment - total*discount < 0){
           System.out.print("您输入的金额小于应付金额，请重新输入：");
           payment = input.nextDouble();
       }
       System.out.println("找钱：" + (payment - total*discount));
   }
}