Question

我有一个简单的登录程序，我非常简单的不安全数据库是文本文件，就是这个

mohammed
badpassword1
fahad
badpassword2
saad
Badpassword3
faisal
badpassword4
jack
badpasswod5

我有这段代码读取文本文件中的每一行并打印出来

我只想传递用户名并获取密码，这是下一行，但我不能我试图将它存储在数组中并从用户名中获取下一个元素的密码，但所有元素都是NULL，我不知道为什么我可以得到一些帮助吗？

public static void main(String[] args) throws Exception{

    try {
        FileReader reader = new FileReader("/Users/mohammed/Downloads/testFile.txt");
        BufferedReader bufferedReader = new BufferedReader(reader);

        String line = new String();

        while ((line = bufferedReader.readLine()) != null) {
            System.out.println(line);
        }
        reader.close();

    } catch (IOException e) {
        e.printStackTrace();
    }
}

Answer 1

我知道这可能是一个有点愚蠢的解决方案，但它应该可行。

public class User {
    private String username;
    private String password;

    // getters, setters, toString
}

....

public static void main(String[] args) throws Exception{

    try {
        FileReader reader = new FileReader("/Users/mohammed/Downloads/testFile.txt");
        BufferedReader bufferedReader = new BufferedReader(reader);

        String line = new String();

        // let's have this one to hold users
        List<User> users = new ArrayList<>();

        int index = 1;
        User user = new User();
        while ((line = bufferedReader.readLine()) != null) {
            now we will read line by line, create User objects and put them into the list
            System.out.println(line);
            if (index > 2) {
                // means you are reading the third line, so that's the name of the next user
                users.add(user); // save previous user
                user = new User(); // object to hold new one
                index = 1; // reset index
            }
            if (index == 1) {
                user.setUserName(line);
            }
            if (index == 2) {
                user.setPassword(line);
            }
            index++;
        }
        reader.close();

    } catch (IOException e) {
        e.printStackTrace();
    }

    // and once you have all the users in the list you can do whatever you need
   //e.g. print all users
   users.forEach(System.out::println);

   // find the user you need, e.g. with name 'fahad'
   final User fahad = users.stream().filter(u -> { return u.getUserName().equals("fahad")}).findFirst();
   System.out.println(fahad.getPassword()); // for instance
}

Answer 2

将您当前阅读的行与您要查找的行（用户名）进行比较并打印下一行

public static void main(String[] args) throws Exception{

try {
    FileReader reader = new FileReader("/Users/mohammed/Downloads/testFile.txt");
    BufferedReader bufferedReader = new BufferedReader(reader);
    String username="mohammed";
    String line = new String();

    while ((line = bufferedReader.readLine()) != null) 
        if(line.equals(username){
            System.out.println(bufferedReader.readLine());
            break;
        }

    reader.close();

} catch (IOException e) {
    e.printStackTrace();
}
}

读取和比较文本文件行

2 个答案: