* #notifyFailed(Throwable)} instead.
   *
   * <p>This method should return promptly; prefer to do work on a different thread where it is
   * convenient. It is invoked exactly once on service startup, even when {@link #startAsync} is
   * called multiple times.
   */
  @ForOverride
  protected abstract void doStart();

  /**

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Preconditions;
import org.jspecify.annotations.Nullable;

/**
 * Implementation of {@link ImmutableSet} with exactly one element.
 *
 * @author Kevin Bourrillion
 * @author Nick Kralevich
 */
@GwtCompatible
@SuppressWarnings("serial") // uses writeReplace(), not default serialization

   */
  protected final void expectContents(E... elements) {
    expectContents(asList(elements));
  }

  /**
   * Asserts that the collection under test contains exactly the given elements, respecting
   * cardinality but not order. Subclasses may override this method to provide stronger assertions,
   * e.g., to check ordering in lists, but realize that <strong>unless a test extends {@link

For example, in one of the ways the OAuth2 specification can be used (called "password flow") it is required to send a `username` and `password` as form fields.

The <abbr title="specification">spec</abbr> requires the fields to be exactly named `username` and `password`, and to be sent as form fields, not JSON.

#### Password hashing { #password-hashing }

"Hashing" means: converting some content (a password in this case) into a sequence of bytes (just a string) that looks like gibberish.

Whenever you pass exactly the same content (exactly the same password) you get exactly the same gibberish.

But you cannot convert from the gibberish back to the password.

##### Why use password hashing { #why-use-password-hashing }

   * @throws IllegalArgumentException if the stream consists of two or more elements.
   * @throws NullPointerException if any element in the stream is {@code null}.
   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be
   *     {@code null}) and returns {@code Optional.empty()} if it has none.
   */
  @SuppressWarnings("unchecked")
  public static <T> Collector<T, ?, Optional<T>> toOptional() {

  std::pair<std::unique_ptr<TensorSliceReader::VarToShapeMap>,
            std::unique_ptr<TensorSliceReader::VarToDataTypeMap> >
  BuildV2VarMaps();

  // Invariant: exactly one of "reader_" and "v2_reader_" is non-null.
  std::unique_ptr<TensorSliceReader> reader_;
  std::unique_ptr<BundleReader> v2_reader_;

  std::unique_ptr<TensorSliceReader::VarToShapeMap> var_to_shape_map_;

	}

	// Assert new checksum matches the content
	matchError := chksmOut.Matches(myData, 0)
	if matchError != nil {
		t.Fatalf("Checksum mismatch on chksmOut: %v", matchError)
	}

	// Assert they are exactly equal
	if !chksmOut.Equal(chksm) {
		t.Fatalf("Checksum mismatch: expected %+v, got %+v", chksm, chksmOut)
	}
}

// TestChecksumSerializeDeserializeMultiPart checks AppendTo can be reversed by ChecksumFromBytes

        format.formatRate(builder, 0.0);
        assertEquals("0.0 B/s", builder.build());

        // Test rate at exactly 1000 (1 kB/s)
        builder = new DefaultMessageBuilder();
        format.formatRate(builder, 1000.0);
        assertEquals("1.0 kB/s", builder.build());

        // Test rate at exactly 1000000 (1 MB/s)
        builder = new DefaultMessageBuilder();
        format.formatRate(builder, 1000000.0);

  if (isEmpty()) return null

  val position = ParsePosition(0)
  var result = STANDARD_DATE_FORMAT.get().parse(this, position)
  if (position.index == length) {
    // STANDARD_DATE_FORMAT must match exactly; all text must be consumed, e.g. no ignored
    // non-standard trailing "+01:00". Those cases are covered below.
    return result
  }
  synchronized(BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS) {