java Jtextfield focusLost 被叫了很多次

Question

大家好，想在 Jtextfield focusLost 检测填写是否正确，可在提示了出错信息后， 本来想返回这个 jtextfield, 不知道为何这个focuslost却被叫了很多次。 private void jTextField1FocusLost(java.awt.event.FocusEvent evt) {                                      
        // TODO add your handling code here:evt.getSource();
        JTextField roomTag=(JTextField) evt.getSource();
         String text = roomTag.getText();
         if (text.length() >= 3) {
            try {
                    Integer.parseInt(text);            } catch(NumberFormatException nfe) {
                 Toolkit.getDefaultToolkit().beep();
SwingUtilities.invokeLater(new FocusGrabber(this.jTextField1));
               JOptionPane.showMessageDialog(null, "It must be a numeric value");               //roomTag.requestFocus();
               //jTextField1.requestFocus();
               //return;
            }
         } else {
               JOptionPane.showMessageDialog(null, "It must be 3 chars at least");
               //roomTag.requestFocus();
                //jTextField1.requestFocus();
                //return;
         }    }