private JFileChooser getClassesFileChooser() {
if (classesFileChooser == null) {
classesFileChooser = new JFileChooser(classesChooserPath);
classesFileChooser.setDialogTitle("Choose class file or jar file");
classesFileChooser.addChoosableFileFilter(new BasicFileFilter("class", "class files"));
classesFileChooser.addChoosableFileFilter(new BasicFileFilter("jar", "jar files"));
classesFileChooser.setFileFilter(new BasicFileFilter(new String[]{"class", "jar"}, "class files and jar files"));
}
return classesFileChooser;
}