@Immutable
@ElementTypesAreNonnullByDefault
public final class ImmutableDoubleArray implements Serializable {
  private static final ImmutableDoubleArray EMPTY = new ImmutableDoubleArray(new double[0]);

  /** Returns the empty array. */
  public static ImmutableDoubleArray of() {
    return EMPTY;
  }

  /** Returns an immutable array containing a single value. */
  public static ImmutableDoubleArray of(double e0) {