购物商品例题：

package ad;

import java.text.DecimalFormat;
import java.util.Scanner;

public class Ts1 {

    public static void main(String[] args) {
        Scanner input = new Scanner (System.in);    //实例化Scanner
        DecimalFormat df = new DecimalFormat("0.0"); //保留1位小数
        int amount = 0;       //数量
        double discount =0.8; //折
        double total =0.0;      //总价
        double payment =0.0;    //实付
        //价格
        double shirt = 188.0;
        double tennis = 280.0;
        double racket = 150.0;
        String k = null ;
        
        System.out.println("1.T恤       2.网球鞋     3.网球拍");
        System.out.println("*************");
        System.out.print("请选择购买的商品编号:");
        int id = input.nextInt();//编号
        System.out.print("请选择购买的商品数量:");
        amount = input.nextInt(); //数量
        
        do {
            //1.T血 
            if (id==1) {
                System.out.println("T恤￥："+shirt+"      "+"数量:"+amount+"   "+"合计￥："+shirt*amount);
                System.out.print("是否继续(y/n):");
                k = input.next();
            }
            //2.网球鞋
            if (id==2) {
                System.out.println("网球鞋￥："+tennis+"      "+"数量:"+amount+"   "+"合计￥："+tennis*amount);
                System.out.print("是否继续(y/n):");
                k = input.next();
                
            }
            //3.网球拍
            if (id==3) {
                System.out.println("网球拍￥："+racket+"      "+"数量:"+amount+"   "+"合计￥："+racket*amount);
                System.out.print("是否继续(y/n):");
                k = input.next();
                
            }
            
        } //输入y继续执行循环，输入n结束循环，执行对应的编号商品进行结账
        while (k=="y");
        //结账T血 
        if (id==1) {
            
            total = (shirt*amount)*discount;
            payment = shirt*amount;
            System.out.println("折扣:"+discount);
            System.out.println("应付金额:"+df.format(total));
            System.out.println("实付金额:"+payment);
            System.out.println("找钱:"+df.format(payment-total));
        }
        //结账网球鞋 
        if (id==2) {
            
            total = (tennis*amount)*discount;
            payment = tennis*amount;
            System.out.println("折扣:"+discount);
            System.out.println("应付金额:"+df.format(total));
            System.out.println("实付金额:"+payment);
            System.out.println("找钱:"+df.format(payment-total));
            
        }
        //结账网球拍
        if (id==3) {
            total = (racket*amount)*discount;
            payment = racket*amount;
            System.out.println("折扣:"+discount);
            System.out.println("应付金额:"+df.format(total));
            System.out.println("实付金额:"+payment);
            System.out.println("找钱:"+df.format(payment-total));
            
        }
        
    }
    
}

运行结果：

java Scanner使用

do-while