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java - 如何在数组中查找元素

问题描述

我目前有一个编程任务。在作业中，我必须有两个数组来存储商店库存的数据。我使用第一个数组供 Manager 访问。我使用第二个数组供 Cashier 访问。

管理员最多可以添加 15 个项目的代码、名称、价格和数量。收银员可以添加任何项目的代码和数量。如果管理器的数组中不存在该代码，程序将自动退出。

两个数组列表的数组元素的顺序不同。那么如何确保收银员输入的商品代码确实存在于经理的数组中呢？

这就是我声明数组的方式：

        String[] stockItemCode = new String[15];
        String[] stockItemName = new String[stockItemCode.length];
        int[] stockItemQuantity = new int[stockItemCode.length];
        double[] stockItemPrice = new double[stockItemCode.length];

        String[] saleItemCode = new String[stockItemCode.length];
        String[] saleItemName = new String[stockItemCode.length];
        int[] saleItemQuantity = new int[stockItemCode.length];
        double[] saleItemPrice = new double[stockItemCode.length];

这是经理输入项目的方式：

// 3- The manager:
// 3.1- The manager has to login to add the items to the inventory list. The username and password are "Manager" and "Man_2020" respectively.
            if (username.equals(managerUsername) && password.equals(managerPassword))
            {
// 3.2- Once the manager is logged in, he will enter the item's code, name, quantity, and price. 
                do
                {
                    System.out.println("Please enter item code: ");
                    stockItemCode[stockItemLimit] = sc.next();

                    System.out.println("Please enter item name: ");
                    stockItemName[stockItemLimit] = sc.next();

                    System.out.println("Please enter item quantity (numbers only): ");
                    stockItemQuantity[stockItemLimit] = sc.nextInt();

                    System.out.println("Please enter item price (numbers only): ");
                    stockItemPrice[stockItemLimit] = sc.nextDouble();

                    stockItemLimit++;
// 3.3- After entering the above information for each item, the program prompts the manager to continue or logout of his account. He has to use 'L' or 'S' to sign-out.
                    System.out.println("Would you like to stop the program? Entering S or L will stop the program");
                    logoutPrompt = sc.next().charAt(0);
                }
                while(!(logoutPrompt == 'L' || logoutPrompt == 'S'));
            }

这就是我尝试比较数组元素的方式（我知道这是错误的，但我不知道为什么。我对编程很陌生）。

// 4- The sales employee:
// 4.1- The sales employee logs in to scan the sold items and print the receipt. The username and password are "Sales" and "Sale_2020" respectively.
            else if (username.equals(salesUsername) && password.equals(salesPassword))
            {
                i = 0;
// 4.2- The sales employee, enters the *code* and the *quantity* of the sold item.
                do
                {
                    System.out.println("Please enter item code: ");
                    saleItemCode[i] = sc.next();

                    System.out.println("Please enter item quantity (numbers only): ");
                    saleItemQuantity[i] = sc.nextInt();

                    saleItemName[i] = stockItemName[i]; //This is the problem
                    saleItemPrice[i] = stockItemPrice[i]; //This is the problem

// 4.3- The program calculates the total price of the transaction, by using the quantity and the price of the sold items.
                    if(saleItemCode[i] == stockItemCode[i])
                    {
                        saleItemPrice[i] = stockItemPrice[i] * saleItemQuantity[i];
// 4.4- The program has to deduct the sold quantity of the items from the stock list.
                        stockItemQuantity[i] = stockItemQuantity[i] - saleItemQuantity[i];
// 4.5- After entering each item, the employee is prompted to continue adding the item to the receipt, or print it (by using 'P').
                        System.out.println("Would you like to print the receipt by entering P? Enter anything else to continue adding items.");
                        logoutPrompt = sc.next().charAt(0);
                    }

                    else
                    {
// If the code is entered incorrectly, the program skips to 4.5.
                        System.out.println("Would you like to print the receipt by entering P? Enter anything else to continue adding items.");
                        logoutPrompt = sc.next().charAt(0);
                    }

                    i++;

                }
                while(logoutPrompt != 'P');

此外，每当我在 Cashier's 循环中尝试打印股票项目的信息时，arrayElements 都会返回 null，就好像它们不存在一样，即使它们显然存在。

for(i = 0; i <= stockItemLimit; i++) //COME HERE
{
int indexNumb = i+1;
System.out.println(indexNumb + "\t" + saleItemCode[i] + "\t" + saleItemName[i] + "\t" + "$" + saleItemPrice[i] + "\t" + saleItemQuantity[i]);
}

所有帮助将不胜感激。

标签： java

解决方案

通过遍历所有元素并比较每个元素，您可以在未排序的数组中找到一个元素。

 int stockitemindex = -1;
 for(int searchindex = 0; searchindex <= stockItemLimit; searchindex++) {
     if (stockItemCode[searchindex].equals(saleItemCode[i])) {
          stockitemindex = searchindex;
          break;
     }
 }

从您的描述中不清楚为什么 stockitem 和 saleitem 的数组具有相同的大小。甚至不清楚您是否需要一个用于 saleitem 的数组。只是一个字符串代码和 int 数量似乎就足够了。

同样在问题结束时的循环中，您访问的是 saleitem 数组，而不是 stockitem 数组，这就是您获得空内容的原因。

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