如何使用 FileReader 逐行读取

Question

感谢您的关注。

我创建了一个程序，我正在使用登录表单和注册表单。 一旦用户注册了他们的电子邮件，他们的密码就会被保存到submit.txt中。 然后他们将返回登录表单并输入保存在submit.txt中的电子邮件和密码。

在我的代码中，我将写入文件用于注册表单，将读取文件用于登录表单。 但是，它不起作用。 我知道我在用于读取文件的代码中存在问题。 你能帮我意识到这一点吗？

非常感谢您的帮助。

 if (checkPassword(usern, hash)) {
    System.out.println("Logged in!");
    ChooseWindow ptb = new ChooseWindow();
    ptb.setVisible(true);
    LoginWindow.this.dispose();
 } else {
    System.out.println("Wrong password");
 }

 public boolean checkPassword(String username, String pass) {
    try {
        FileReader inFile = new  FileReader("/users/Ender/Desktop/GetUser/submit.txt");
        BufferedReader inStream = new BufferedReader(inFile);
        String inString;

        while ((inString = inStream.readLine()) != null) {}
        inStream.close();                       
    }catch (IOException e) {
        e.printStackTrace();
    }
    return false;
 }

Answer 1

这是我从文件中读取的代码：

 String line;

    try {

        BufferedReader bufferreader = new BufferedReader(new FileReader("C:\\Users\\ahmad\\Desktop\\aaa.TXT"));


        while ((line = bufferreader.readLine()) != null) {     
          /** 
            Your implementation  
          **/

        }

    } catch (FileNotFoundException ex) {
        ex.printStackTrace();
    } catch (IOException ex) {
        ex.printStackTrace();
    }

Answer 2

假设我们有一个username和hash存储如下的文件：

你好世界
测试一下
哑用户 12345
用户 sjklfashm-0998() ( &

我们想使用每行中的第一个单词作为username ，第二个作为password / hash 。 那么想法是：

• 读一行
• 在“”处将行分成几部分
• 将第一部分与username进行比较，将第二部分与pass
• 如果有匹配返回true，否则重新开始

这导致此代码：

public boolean checkPassword(String username, String pass) {
    // if there is no username or no password you can not log in
    if(username == null || pass == null){ // diff
        return false;                     // diff
    }                                     // diff
    try {
        FileReader inFile = new  FileReader(PASSWORD_FILE);
        BufferedReader inStream = new BufferedReader(inFile);
        String inString;

        while ((inString = inStream.readLine()) != null) {
            // we split every line into two parts separated by a space " "
            String usernameHash[] = inString.split(" "); // diff
            // if there are more or less than two parts this line is corrupted and useless
            if(usernameHash.length == 2                  // diff
                    && username.equals(usernameHash[0])  // diff
                    && pass.equals(usernameHash[1])){    // diff
                // if username matches the first part and hash the second everything is goo
                return true;                             // diff
            }                                            // diff
        }
        inStream.close();
    }catch (IOException e) {
        e.printStackTrace();
    }
    return false;
}

我用// diff标记了我的代码与您的代码不同的部分

Answer 3

 try {
        FileReader inFile = new  FileReader("/users/Ender/Desktop/GetUser/submit.txt");
        BufferedReader inStream = new BufferedReader(inFile);
        List<String> lines = inStream.Lines().toList();
        String username=lines[0];
        String password=lines[1];    
    }

Answer 4

您可以使用以下代码读取文件..

    try {
        BufferedReader bufferreader = new BufferedReader(new FileReader("./users/Ender/Desktop/GetUser/submit.txt"));
        String line;

        while ((line = bufferreader.readLine()) != null) {
            // line variable contains the readed line
            // You can append it to another String to get the whole text or anything you like
        }

    } catch (FileNotFoundException ex) {
        ex.printStackTrace();
    } catch (IOException ex) {
        ex.printStackTrace();
    }

如果要编写文件，请使用以下代码..

    BufferedWriter writer = new BufferedWriter(new FileWriter("./users/Ender/Desktop/GetUser/submit.txt")); 
    writer.write(your_text);
    writer.close();

如果要附加文本，请使用以下代码创建BufferedWriter的实例

    BufferedWriter writer = new BufferedWriter(new FileWriter("/users/Ender/Desktop/GetUser/submit.txt", true));