LinearId implements Id { @Override public String get(int index) { return data_[index]; } LinearId();  LinearId(String id);  LinearId(String parent, String tail);  LinearId(String... id);  LinearId(String[] ids, IdAggregator aggregator); private  LinearId(String[] ids, IdAggregator aggregator, Void private_constructor); @NonNull static LinearId of(@NonNull Id id); @Override String get(int index); @Override LinearId extend(String tail); @Override LinearId parent(); @Override int getCount(); @Override boolean equals(Object obj); @Override int hashCode(); @Override String toString(); @Override String[] toArray();  }
@Test public void testGet() { assertThatThrownBy(() -> empty.get(0)).isInstanceOf(NullPointerException.class); assertThat(single.get(0)).isEqualTo("single"); assertThat(dual.get(0)).isEqualTo("hello"); assertThat(dual.get(1)).isEqualTo("world"); }