JTextArea/JTextComponent setText вызывает сбой

Я новичок в Java в целом и, в частности, в библиотеке Swing. Когда я экспериментировал со стандартной демо-версией Notepad (из JDK ), у меня произошел сбой при попытке изменить текст в окне редактора. Мой пример кода:

void Filter(Component f){
  if (f instanceof JTextComponent){
    JTextComponent textComponent = (JTextComponent) f;
    textComponent.setVisible(false); //Works
    textComponent.setVisible(true); //Works
    textComponent.getText(); //Works
    textComponent.updateUI(); //Works
    textComponent.setText("Hello world!"); //Crashes
  }else{
    RecursiveGet(f);
  }
}
void RecursiveGet(Component c){
  for (Component f : ((JComponent) c).getComponents()) {
    if (f instanceof JComponent) {
      Filter(f);
    }
  }
}

Я искал, например, JTextComponent , пока не нашел его, а затем протестировал некоторые методы. Я думаю, что я что-то упускаю, некоторые детали. Моя среда JDK 1.7, JRE 7.0, Win7 x64. Буду рад любой помощи. Спасибо.

Обновление Я добавляю обработчик исключений

void Filter(Component f){
        if (f instanceof JTextComponent){
            JTextComponent textComponent = (JTextComponent) f;
            textComponent.setVisible(false);  //Work
            textComponent.setVisible(true);  //Work
            textComponent.getText();  //Work
            textComponent.updateUI(); //Work
            try {
            textComponent.setText("Hello world!"); //Crash
            } catch (Exception e) {
                e.printStackTrace();
            }
        }else{
            RecursiveGet(f);
        }
    }

и получить это..

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at javax.swing.plaf.synth.SynthContext.getPainter(Unknown Source)
        at javax.swing.plaf.synth.SynthTextAreaUI.update(Unknown Source)
        at javax.swing.JComponent.paintComponent(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JViewport.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JComponent.paintChildren(Unknown Source)
        at javax.swing.JComponent.paint(Unknown Source)
        at javax.swing.JComponent.paintToOffscreen(Unknown Source)
        at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown S
ource)
        at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
        at javax.swing.RepaintManager.paint(Unknown Source)
        at javax.swing.JComponent._paintImmediately(Unknown Source)
        at javax.swing.JComponent.paintImmediately(Unknown Source)
        at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
        at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
        at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
        at javax.swing.RepaintManager.access$700(Unknown Source)
        at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
        at java.awt.event.InvocationEvent.dispatch(Unknown Source)
        at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
        at java.awt.EventQueue.access$000(Unknown Source)
        at java.awt.EventQueue$3.run(Unknown Source)
        at java.awt.EventQueue$3.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Sour
ce)
        at java.awt.EventQueue.dispatchEvent(Unknown Source)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.run(Unknown Source)

Обновление 2 Метод setText работает после добавления блока обработчика исключений. Но что мне не хватает?