public void testHashCode() {
        CategoryPointerAnnotation a1 = new CategoryPointerAnnotation("Label",
                "A", 20.0, Math.PI);
        CategoryPointerAnnotation a2 = new CategoryPointerAnnotation("Label",
                "A", 20.0, Math.PI);
        assertTrue(a1.equals(a2));
        int h1 = a1.hashCode();
        int h2 = a2.hashCode();
        assertEquals(h1, h2);