java - 写入和读取文件时出现问题

Question

我是编程新手(抱歉，如果我问一个简单的问题)，我的程序在处理文件写入和读取时遇到问题。首先，我询问用户他们想要的用户名和密码是什么。然后，为了简单地检查我所做的是否正确，我尝试读取该文件，然后打印出相同的信息。这是我的代码:

public void createAccount()
{
    try
    {
        FileWriter doc = new FileWriter("Username.ctxt", true);
        System.out.print("Enter your desired Username: ");
        myUsername = keyboard.next();
        System.out.println();
        System.out.print("Enter your desired Password: ");
        myPassword = keyboard.next();
        System.out.println();
        String doc2 = myUsername + " " + myPassword + "\n";
        doc.write(doc2, 0, doc2.length());
        doc.close();
    }
    catch(IOException e)
    {
        System.out.println("Error: " + e.getMessage());
   }

   retrieveAccount();
}

public void retrieveAccount()
{
    try
    {
        BufferedReader reader = new BufferedReader(new FileReader("Username.ctxt"));//
        String user = new String("");//username
        String pass = new String("");//password
        int stop;
        String line = null;

        System.out.print("Enter your username: ");//allows computer to search through file and find username
        username = keyboard.next();
        while ((line = reader.readLine()) != null) 
        {
            scan = reader.readLine();
            stop = scan.indexOf(" ");
            user = scan.substring(0, stop);
            System.out.println(user);
            pass = scan.substring(stop + 1);
            System.out.println(pass);
            if(user.equals(myUsername))
            {
                System.out.println("Your password is: " + pass);
                break;
            }
        }
    }
    catch(IOException a)
    {
        System.out.println("Error: " + a.getMessage());
    }
}

所以我想要发生的是:

Enter desired username: jake101
Enter desired password: coolKid

Enter your username: jake101
your password is: coolKid

但实际发生的是，是越界异常(-1)

发生这种情况是因为当我使用 indexOf(""); 时它会搜索空格。当它返回负 1 时，意味着没有空间。我相信正在发生的事情是我没有写入我试图读取的同一个文档。如果有人可以帮助我找出我做错了什么，这会有所帮助!

Answer 1

您正在重复读取文件的内容...

您首先使用...从文件中读取一行

while ((line = reader.readLine()) != null) {

紧接着，您使用...阅读了另一行

String scan = reader.readLine();

删除第二行读取...