Hide input on command line

Question

I know that command line interfaces like Git and others are able to hide input from a user (useful for passwords). Is there a way to programmtically do this in Java? I'm taking password input from a user and I would like their input to be "hidden" on that particular line (but not on all of them). Here's my code for it (though I doubt it would be helpful...)

try (Scanner input = new Scanner(System.in)) {   //I'm guessing it'd probably be some property you set on the scanner or System.in right here...   System.out.print("Please input the password for " + name + ": ");   password = input.nextLine(); } 

Answer 1

Try java.io.Console.readPassword. You'll have to be running at least Java 6 though.

   /**     * Reads a password or passphrase from the console with echoing disabled     *     * @throws IOError     *         If an I/O error occurs.     *     * @return  A character array containing the password or passphrase read     *          from the console, not including any line-termination characters,     *          or <tt>null</tt> if an end of stream has been reached.     */     public char[] readPassword() {         return readPassword("");     } 

Beware though, this doesn't work with the Eclipse console. You'll have to run the program from a true console/shell/terminal/prompt to be able to test it.

Answer 2

Yes can be done. This is called Command-Line Input Masking. You can implement this easily.

You can uses a separate thread to erase the echoed characters as they are being entered, and replaces them with asterisks. This is done using the EraserThread class shown below

import java.io.*;  class EraserThread implements Runnable {    private boolean stop;     /**     *@param The prompt displayed to the user     */    public EraserThread(String prompt) {        System.out.print(prompt);    }     /**     * Begin masking...display asterisks (*)     */    public void run () {       stop = true;       while (stop) {          System.out.print("\010*");      try {         Thread.currentThread().sleep(1);          } catch(InterruptedException ie) {             ie.printStackTrace();          }       }    }     /**     * Instruct the thread to stop masking     */    public void stopMasking() {       this.stop = false;    } } 

With using this thread

public class PasswordField {     /**     *@param prompt The prompt to display to the user     *@return The password as entered by the user     */    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();       }       // stop masking       et.stopMasking();       // return the password entered by the user       return password;    } } 

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