Below is the code for the UsernamePasswordCallbackHandler used in this tutorial. It is called once by the AlwaysLoginModule (with only one callback to get the userid) and once by the PasswordLoginModule (with two callbacks to get both a user ID and password).

import java.io.*;
import java.security.*;
import javax.security.auth.*;
import javax.security.auth.callback.*;
//
// This class implements a username/password callback handler that gets 
// information from the user public class
UsernamePasswordCallbackHandler implements CallbackHandler {
     //
     // The handle method does all the work and iterates through the array
     // of callbacks, examines the type, and takes the appropriate user
     // interaction action.
     public void handle(Callback[] callbacks) throws
         UnsupportedCallbackException, IOException {

       for(int i=0;i<callbacks.length;i++) {
         Callback cb = callbacks[i];
         //
         // Handle username aquisition
         if (cb instanceof NameCallback) {
           NameCallback nameCallback = (NameCallback)cb;
           System.out.print( nameCallback.getPrompt() + "? ");
           System.out.flush();
           String username = new BufferedReader(
               new InputStreamReader(System.in)).readLine();
           nameCallback.setName(username);
           //
           // Handle password aquisition
         } else if (cb instanceof PasswordCallback) {
           PasswordCallback passwordCallback = (PasswordCallback)cb;
           System.out.print( passwordCallback.getPrompt() + "? ");
           System.out.flush();
           String password = new BufferedReader(
               new InputStreamReader(System.in)).readLine();
           passwordCallback.setPassword(password.toCharArray());
           password = null;
           //
           // Other callback types are not handled here
         } else {
           throw new UnsupportedCallbackException(cb, "Unsupported 
Callback Type");
         }
       }
     }
}