Question

该程序要求我要求用户输入一个菜单项及其价格并继续这样做，直到用户输入0.然后用户输入“1”以查看菜单项和价格列表。这是代码：

import java.util.*;
import java.io.*;
public class Restaurant Trial {
final static int Max=100;

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    String[]item_name=new String[Max];
    double[]item_price=new double[Max];
    int totalitems=0;
    int n=0;
    String trap;

    System.out.printf("\nEnter the name of item followed by its price: \nEnter '0' to stop\n");

    String name=in.nextLine();
    trap = in.nextLine();
    double price=in.nextDouble();
    while (name!="") {
        totalitems++;
        item_name[n++]=name;
        item_price[n++]=price;
        System.out.printf("\nEnter the name of item followed by its price: \nEnter '0' to stop\n");
        trap=in.nextLine();
        name=in.nextLine();
        if ("0".equals(name))
            break;
        price=in.nextDouble();
    }//end while
    int lo=1;

    System.out.printf("\nEnter 1 to view all menu items and prices\n" +
                      "Enter 2 to  view the price of a menu item\n"+
                      "Enter 3 to edit the price of a menu item\n" +
                      "Enter 4 to add an item to the menu\n" +
                      "Enter 5 to exit the program\n");
    int action = in.nextInt();
    if (action==1) {
        System.out.printf("MENU ITEM              PRICE");
        for (int l=1; l<=totalitems; l++) {
            System.out.printf("\n%s                  $%3.2f", item_name[l], item_price[l]);
        }

    }



}//end main

输入“1”打印输出时出现问题。以下是输出示例：

Enter the name of item followed by its price: 
Enter '0' to stop
chicken
3.50

Enter the name of item followed by its price: 
Enter '0' to stop
rice
4.90

Enter the name of item followed by its price: 
Enter '0' to stop
fish
12.9

Enter the name of item followed by its price: 
Enter '0' to stop
pasta
13.45

Enter the name of item followed by its price: 
Enter '0' to stop
0

Enter 1 to view all menu items and prices
1
MENU ITEM              PRICE
null                  $3.50
rice                  $0.00
null                  $4.90
fish                  $0.00
Process completed.

哦，只是添加，我使用变量'trap'来尝试保持程序在我按下Enter时所接受的换行符。如果有人可以提供任何建议，我们将不胜感激。

Answer 1

看起来是因为您在存储项目的两行上递增n：

item_name[n++]=name;
item_price[n++]=price;

Answer 2

在这里，你要两次递增n：

  item_name[n++]=name;
  item_price[n++]=price;

要修复，请将其更改为

  item_name[n]=name;
  item_price[n++]=price;

数组中的每个其他值都打印为Null

2 个答案: