final JButton btnPotvrda = new JButton(MainFrame.getInstance().getResourceBundle().getString("btnPotvrda"));
		btnPotvrda.addActionListener(new ActionListener() {

			@Override
			public void actionPerformed(ActionEvent e) {


				if(tfUser.getText().trim().length()==0 ||
	                    tfPass.getText().trim().length()==0){
	                             if(tfUser.getText().trim().length()==0)
	                                     tfUser.setBackground(Color.RED);
	                             if(tfUser.getText().trim().length()==0)
	                                     tfPass.setBackground(Color.RED);

	                             JOptionPane.showMessageDialog(null,MainFrame.getInstance().getResourceBundle().getString("Warning"));
	                             tfUser.setBackground(Color.WHITE);
	                             tfPass.setBackground(Color.WHITE);





					}
	             }
	     });