Empty while-loop taking too much power

Question

Hi all!
Would someone help me out with a better implementation of the below code. 'guard' is a class handling validation of users againt a database. I'm waiting for it to finish in an empty while loop in my GUI-class (extending JFrame). This obviously takes all CPU causing bad response time. Any smart suggestion on how to reduce this in my case?
Thanks in advance.
//Wait for the guard to validate user
while(guard.getGrantedPermission() == guard.PENDING) {}
if(guard.getGrantedPermission() == guard.ACCESS_ALLOWED) {
    setVisible(true);
* We should be able to work with the config object since it should
* be initialized when the password dialog prompts the user
   try {
      user = guard.getValidatedUsername();
      //Set the name of the customer
      config = new Config(user, new Date());
   } catch(NullPointerException npe) {
      npe.printStackTrace();
}

Answer 1

Don't use an empty while loop. It's a terrible construct. Listen to zurdo (the first reply). Don't use Thread.sleep() either, as it's inappropriate in your case.
If you don't want to use Observer and Observable, then use a new Thread using the wait() and notifyAll() constructs. See the tutorial at
http://java.sun.com/docs/books/tutorial/essential/threads/index.html
Pay careful attention to its warnings, though.