密码暗示提示

import java.io.BufferedReader;
import java.io.InputStreamReader;

class  passwordTest
{
  public static void main(String[] args) throws Exception
  {
        String pwd = null;
      System.out.println("请输入您的密码:");
      pwd = getStr();
  }
  public static String getStr()throws Exception
  {
    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    Eraser es=new Eraser();
    Thread t=new Thread(es);
    t.start();
    Thread.yield();
    String str=br.readLine();
    return str;
  }
}
class Eraser implements Runnable
{
  boolean flag=true;
  public void run()
  {
     while(flag)
    {
       System.out.print("\b*");
    }
  }
};