During input of password from user on the console, display asterisk(*) sign instead of plain text

Question

I have tried the following codes both have different approaches.

Approach 1: It breaks when executing in the latest version of Eclipse IDE say 2020-03 whereas it works fine in Mars IDE.

This problem is already asked on this How to display asterisk for input in Java?.

Approach 1:

Package test;

import java.io.*;

public class Test {
    public static void main(final String[] args) {
        String password = PasswordField.readPassword("Enter password:");
        System.out.println("Password entered was:" + password);
    }
}

class PasswordField {

    public static String readPassword(String prompt) {
        EraserThread et = new EraserThread(prompt);
        Thread mask = new Thread(et);
        mask.start();

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String password = "";

        try {
            password = in.readLine();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
        et.stopMasking();
        return password;
    }
}

class EraserThread implements Runnable {
    private boolean stop;

    public EraserThread(String prompt) {
        System.out.print(prompt);
    }

    @SuppressWarnings("static-access")
    public void run() {
        while (!stop) {
            System.out.print("\010*");

            try {
                Thread.sleep(1);
            } catch (InterruptedException ie) {
                ie.printStackTrace();
            }

        }
    }

    public void stopMasking() {
        this.stop = true;
    }
}

Approach 2:

It does not work on Eclipse IDE but does work on the command line.

import java.io.Console;
public class Main {

    public void passwordExample() {        
        Console console = System.console();
        if (console == null) {
            System.out.println("Couldn't get Console instance");
            System.exit(0);
        }

        console.printf("Testing password%n");
        char[] passwordArray = console.readPassword("Enter your secret password: ");
        console.printf("Password entered was: %s%n", new String(passwordArray));

    }

    public static void main(String[] args) {
        new Main().passwordExample();
    }
}

Answer 1

Your program for approach 1 doesn't work because it seems the eraser thread isn't closed. You should change your initial boolean value on stopMasking to false, and then tell set it to true after your catch. There's a number of resources available with code that does EXACTLY this. The best one I found is here:

http://www.cse.chalmers.se/edu/year/2018/course/TDA602/Eraserlab/pwdmasking.html

That runs in my Eclipse 2020 build. As far as your second approach, console does not work for user input within an IDE, hence the issues in there but none from command line. If you want to use this version, you could replace console with a scanner:

 import java.util.Scanner

 Scanner input = new Scanner(System.in);
 String password = input.nextLine();
 //implementation

I'd also suggest importing specific class files you need. Importing all of java.io will bog down your program. Hope that helps!