public static String toShortString(Object obj) {
        if (obj == null) {
            return "null";
        }
        return obj.getClass().getSimpleName() + "@" + System.identityHashCode(obj);
    }
@Test
    void testToShortString() {
        assertThat(ClassUtils.toShortString(null), equalTo("null"));
        assertThat(ClassUtils.toShortString(new ClassUtilsTest()), startsWith("ClassUtilsTest@"));
    }