我如何在Java中读取特定数据

Question

How i can read specific data in java

New I write username and password in file text like that ID:username:password

How I can read this data please ? And my program knews this is username and that password 😁

Answer 1

If I understand correctly, the easiest way is to read the text file and parse it into variables accordingly as follows:

BufferedReader br = new BufferedReader(new FileReader("file.txt"));
try {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();
    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    }
    String text= sb.toString();
    String parts = text.split(":")
    String id= parts[0]
    String username = parts[1]
    String pass = parts[2]
} finally {
    br.close();
}

Answer 2

If there is only one entry, you can use the code below, which is quite similar to the first answer, but without the StringBuilder stuff.

try {
    BufferedReader reader = new BufferedReader(new FileReader(new File("file.txt")));
    String line = reader.readLine();
    String[] parts = line.split(":");
    String id = parts[0];
    String username = parts[1];
    String password = parts[2];
    //Do stuff with it
}catch(IOException e){
    e.printStackTrace();
}

However if there are multiple entries, you should use NIO:

try{
    List<String> filecontents = Files.readAllLines(new File("file.txt"));
    for(int i = 0; i < filecontents.size(); i++){
        String line = filecontents.get(i);
        String[] parts = line.split(":");
        String id = parts[0];
        String username = parts[1];
        String password = parts[2];
        //Do stuff with it
    }
}catch(IOException e){
    e.printStackTrace();
}