A custom file chooser that will change the state of the Open button when the user clicks on a file

MyFileChooser.java

public class MyFileChooser extends JFileChooser {
 
  public MyFileChooser() {
    setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
    addPropertyChangeListener(new MyListener());
  }
 
  private class MyListener implements PropertyChangeListener {
    public void propertyChange(PropertyChangeEvent event) {
      String property = FileChooser.SELECTED_FILE_CHANGED_PROPERTY;
      if (!property.equals(event.getPropertyName())) {
        return;
      }
 
      if (!(event.getNewValue() instanceof File)) {
        return;
      }
 
      File file = (File) event.getNewValue();
      boolean flag = true; // insert your logic here
      setOpenButtonState(MyFileChooser.this, flag);
      repaint();
    }
  }
 
  public static void setOpenButtonState(Container c, boolean flag) {
    int len = c.getComponentCount();
    for (int i = 0; i < len; i++) {
      Component comp = c.getComponent(i);
 
      if (comp instanceof JButton) {
        JButton b = (JButton) comp;
 
        if (b.getText().equals("Open") ) {
          b.setEnabled(flag);
        }
      }
      else if (comp instanceof Container) {
        setOpenButtonState((Container) comp, flag);
      }
    }
  }     
}