public ResourceSet filterByClassname(String className) {
    ResourceSet result = new ResourceSet();
    for (Resource r : this) {
      if (r.getClassName().equals(className)) {
        result.add(r);
      }
    }
    return result;
  }
@Test
  void testFilterByClassName() {
    ResourceSet set = new ResourceSet();

    set.add(new Resource(null, new ResourceId("poo1", "resource1"), "value1"));
    set.add(new Resource(null, new ResourceId("poo1", "resource2"), new Integer(2)));

    assertEquals(1, set.filterByClassnameRegex(".*String").size());
    assertEquals(1, set.filterByClassnameRegex(String.class.getName()).size());
    assertEquals(1, set.filterByClassnameRegex(".*Integer").size());
    assertEquals(1, set.filterByClassnameRegex(Integer.class.getName()).size());
  }