### Question:
Optional { @NonNull public static <T> Optional<T> empty() { return (Optional<T>) EMPTY; } private  Optional(@Nullable T value); @NonNull static Optional<T> empty(); @NonNull static Optional<T> of(@Nullable T value); @NonNull T get(); boolean isPresent(); @NonNull T or(@NonNull T defaultValue); @Nullable T orNull(); @Override boolean equals(Object o); @Override int hashCode(); @Override String toString();  }### Answer:
@Test public void emptyReturnsTheSameInstance() { assertThat(Optional.empty()).isSameAs(Optional.empty()); }