src/jdk.scripting.nashorn.shell/share/classes/jdk/nashorn/tools/jjs/NashornCompleter.java

*** 252,261 ****
--- 252,266 ----
  
      // Internals only below this point
  
      // read file name from the user using by showing a swing file chooser diablog
      private static String readFileName(final PrintWriter err) {
+         // if running on AWT Headless mode, don't attempt swing dialog box!
+         if (Main.HEADLESS) {
+             return null;
+         }
+ 
          final FutureTask<String> fileChooserTask = new FutureTask<String>(() -> {
              // show a file chooser dialog box
              final JFileChooser chooser = new JFileChooser();
              chooser.setFileFilter(new FileNameExtensionFilter("JavaScript Files", "js"));
              final int retVal = chooser.showOpenDialog(null);