Subsequent to the JDK 9 fix for 8039383: NPE when changing Windows theme
a hang is seen in SwingSet2 when displaying the JFileChooser in Win L&F.

This trivial program is enough to reproduce it.
import javax.swing.*;

public class Freeze {
  public static void main(String args[]) {
     SwingUtilities.invokeLater(new Runnable() {
        public void run() {
          JFrame f = new JFrame("Freeze");
          f.setSize(100,100);
          f.show();
          try {
             UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
          } catch (Exception e) {
          }
          JFileChooser fileChooser = new JFileChooser(); 
          System.out.println("chooser="+fileChooser);
       }
     });
   }

}