为什么我的方法会覆盖数组中的位置

Question

所以我这里有这个方法

    while(oMenu == 1 || oMenu == 2){
            oMeny = Kbd.readInt("\nClick 1 to make an account\nClick 2 to login\nClick 3 to exit the program");
            if(oMeny == 1){
                for(int i = 0; Account[i] != null; i++){
                    if(Account[i] == null){
                        pos = i;
                    }
                }

                Account[pos] = new Account();


            }

            if(oMeny == 2){
                String s = Kbd.readString("Input your accountnumber: ");
                for(int i = 0; Account[i] != null; i++){
                    if(Account[i] != null && s.equals(Account[i].getAccountNumber())){
                        System.out.println("Welcome!");
                         // Here is rest of my code , the "inner" menu that works menyMetod(iMeny,mMeny);
                    }
                    else{
                        System.out.println("There are no accounts with that given accountnumber!");  
                    }
                }                
            }

        }
    }

我想了解为什么如果我访问 oMeny == 1 并创建 2 个帐户为什么我似乎无法访问我创建的第一个帐户而是最新的帐户？似乎不知何故我的数组 "overwrites" 第一个空位置。基本上我想在我的数组中找到第一个空位置，所以在第一种情况下它总是索引 0 然后下次我再次创建帐户时，逻辑上它应该是索引 1。

编辑：这是我的帐户代码 class

public class Account{

private int money, transactions;
private String AccountNumber;

public Account(){
    money = Kbd.readInt("\nHow much money do you want to put in?");
    AccountNumber = Kbd.readString("\nWhat account number do you want?");
}

Answer 1

您没有显示 pos 的声明或初始化，所以我认为它没有按照您的预期工作，因为您没有进入 Account[i] 为 null 的 for 循环来设置 pos。试试这个

 if(oMenu == 1){
    int pos = 0;
    while (Account[pos] != null && pos < Account.length)
        pos++;
    if (pos < Account.length)
        Account[pos] = new Account();
    else{
         //expand array and add account or throw error
    }
 }

Answer 2

错误在这里：

for (int i = 0; accounts[i] != null; i++) {
     if (accounts[i] == null)

只要 i 指向非空条目，for 循环就会重复。因此 if 条件永远不会为真。

当您在调试器中逐行运行程序时，这一点很快就会变得明显。

下次请提供完整的可以编译的代码示例。你的代码满是错误，我花了很多时间才能够执行它。

更正后的代码：

import java.util.Scanner;

class Main
{
    static Scanner kbd = new Scanner(System.in);
    static Account[] accounts = new Account[100];

    static class Account
    {
        //public int money;
        public String accountNumber;

        public Account()
        {
            //System.out.println("\nHow much money do you want to put in?");
            //money = Kbd.nextInt();
            System.out.println("\nWhat account number do you want?");
            accountNumber = kbd.next();
        }
    }

    public static void main(String[] args)
    {
        int oMenu = 1;
        int pos = 0;
        while (oMenu == 1 || oMenu == 2)
        {
            System.out.println("\nClick 1 to make an account\nClick 2 to login\nClick 3 to exit the program");
            oMenu = kbd.nextInt();
            if (oMenu == 1)
            {
                for (int i = 0; i<accounts.length; i++)
                {
                    if (accounts[i] == null)
                    {
                        accounts[i] = new Account();
                        break;
                    }
                }
            }

            if (oMenu == 2)
            {
                System.out.println("Input your accountnumber: ");
                String s = kbd.next();
                Account found=null;
                for (int i = 0; i<accounts.length; i++)
                {
                    if (accounts[i] != null && s.equals(accounts[i].accountNumber))
                    {
                        found=accounts[i];
                    }
                }
                if (found!=null)
                {
                    System.out.println("Welcome! nr. "+found.accountNumber);
                }
                else
                {
                    System.out.println("There are no accounts with that given accountnumber!");
                }
            }
        }
    }
}

请注意我还修复了第二个 for 循环。

为什么我的方法会覆盖数组中的位置

Why does my method overwrite positions in my array

java

arrays

account

logic

while-loop