EventQueue.invokeLater(new Runnable() {
            public void run() {
                Long hrg;
                hrg = (Long)thrg.getValue();
                if (hrg != null && hrg < 0) { 
                    JOptionPane.showMessageDialog(this, "Kolom ini Harus di Isi Numerik", "Informasi", JOptionPane.INFORMATION_MESSAGE);  
                    thrg.setText("");
                    thrg.requestFocus();
                }
            }
        });{
           
       }