java - 如何从输入文件中读取指定的字符串，然后读取其后面的下一个单词

Question

在 Java 中，我希望能够有两个接受 String 的 JTextField。一个是用户名，另一个是密码。要“登录”，程序将搜索文件 -->accounts.txt 并首先搜索“usrnm:”，一旦找到它，它就会在以下单词之后查找: 密码也是如此，但它搜索“pswrd:”。

这是我到目前为止所得到的:

    public void checkCredentials() {
    try {
        BufferedReader br = new BufferedReader(new FileReader(new File("accounts.txt")));
        String text = br.readLine();
        text = text.toLowerCase();
        text.split("usrnm:");
        System.out.println("username: " + userInput);
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

感谢任何帮助!

Answer 1

我认为最好先保存用户名，然后在下一行保存密码，而不是搜索文件两次。当您阅读它们时，您可以创建具有以下属性(用户名和密码(字符串))的 User 对象。您也可以在系统处于 Activity 状态时将它们保存到链接列表中。这样您就可以轻松访问用户帐户。一旦用户需要登录，您将扫描列表并使用 userList.get(i).equals(textfield.getText()) 您将确定所询问的用户。之后，如果上述语句成立，您将检查 userList.get(i).getPassword().equals(textfield2.getText()) 是否为 true，并相应地授予或拒绝访问。

我在下面提供了一些有用的部分。

    public void readFromFile(String fileName, ListInterface<User> userList) {
        String oneLine, oneLine2;
        User user;
        try {
            /*
             * Create a FileWriter object that handles the low-level details of
             * reading
             */
            FileReader theFile = new FileReader(fileName);

            /*
             * Create a BufferedReader object to wrap around the FileWriter
             * object
             */
            /* This allows the use of high-level methods like readline */
            BufferedReader fileIn = new BufferedReader(theFile);

            /* Read the first line of the file */
            oneLine = fileIn.readLine();
            /*
             * Read the rest of the lines of the file and output them on the
             * screen
             */
            while (oneLine != null) /* A null string indicates the end of file */
            {
                oneLine2 = fileIn.readLine();
                user = new User(oneLine, oneLine2);
                oneLine = fileIn.readLine();
                userList.append(user);
            }

            /* Close the file so that it is no longer accessible to the program */
            fileIn.close();
        }

        /*
         * Handle the exception thrown by the FileReader constructor if file is
         * not found
         */
        catch (FileNotFoundException e) {
            System.out.println("Unable to locate the file: " + fileName);
        }

        /* Handle the exception thrown by the FileReader methods */
        catch (IOException e) {
            System.out.println("There was a problem reading the file: "
                    + fileName);
        }
    } /* End of method readFromFile */


    public void writeToFile(String fileName, ListInterface<User> userList) {
        try {
            /*
             * Create a FileWriter object that handles the low-level details of
             * writing
             */
            FileWriter theFile = new FileWriter(fileName);

            /* Create a PrintWriter object to wrap around the FileWriter object */
            /* This allows the use of high-level methods like println */
            PrintWriter fileOut = new PrintWriter(theFile);

            /* Print some lines to the file using the println method */
            for (int i = 1; i <= userList.size(); i++) {
                fileOut.println(userList.get(i).getUsername());
                fileOut.println(userList.get(i).getPassword());
            }
            /* Close the file so that it is no longer accessible to the program */
            fileOut.close();
        }

        /* Handle the exception thrown by the FileWriter methods */
        catch (IOException e) {
            System.out.println("Problem writing to the file");
        }
    } /* End of method writeToFile */

• userList 是一个使用泛型的动态链表 (ListInterface<User>)

  如果你不想使用泛型，你可以只说ListInterface userList，无论它出现在哪里。

  • 您的 User 类应实现类似的方法并包含以下方法:

  public int compareTo(User user) {
  
  }
  
  public boolean equals(Object user) {
  
  }
  

  • 请注意，如果您不使用泛型，则可能需要类型转换。否则，您将收到编译错误。