Region { public static Region of(String region) { Preconditions.checkNotNull(region); return new Region(region); } private  Region(String region); static Region of(String region); software.amazon.awssdk.regions.Region asAws(); @Override boolean equals(Object o); @Override int hashCode(); @Override String toString();  }
@Test void shouldNotAcceptNullRegion() { assertThatThrownBy(() -> Region.of(null)).isInstanceOf(NullPointerException.class); }