/**
   * A collector that converts a stream of zero or one elements to an {@code Optional}.
   *
   * @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

    worked everywhere that I know of except for one place: when running the GWT
    util.concurrent tests under Guava.

    The problem is that GWT responds poorly to two .gwt.xml files in the same
    Java package; see
    https://groups.google.com/g/google-web-toolkit-contributors/c/CqYH59Dt_rQ/m/uVGW1QdUsXUJ
    for details.

    The summary is that it ignores one file in favor of the other.

growing, and very soon had to kneel down on the floor:  in
another minute there was not even room for this, and she tried
the effect of lying down with one elbow against the door, and the
other arm curled round her head.  Still she went on growing, and,
as a last resource, she put one arm out of the window, and one
foot up the chimney, and said to herself `Now I can do no more,
whatever happens.  What WILL become of me?'

     * @param source A hint about the source of the problem like a file path, may be {@code null}.
     * @param lineNumber The one-based index of the line containing the problem or {@code -1} if unknown.
     * @param columnNumber The one-based index of the column containing the problem or {@code -1} if unknown.
     * @param exception The exception that caused this problem, may be {@code null}.
     */

  @CollectionSize.Require(absent = {ZERO, ONE})
  public void testCreateWithDuplicates_nullDuplicatesNotRejected() {
    expectFirstRemoved(getEntriesMultipleNullKeys());
  }

  @MapFeature.Require(absent = REJECTS_DUPLICATES_AT_CREATION)
  @CollectionSize.Require(absent = {ZERO, ONE})
  public void testCreateWithDuplicates_nonNullDuplicatesNotRejected() {

environment.title = Production

# Does it enable the Framework internal debug? (true only when emergency)
framework.debug = false

# one day: 86400000, three days: 259200000, five days: 432000000, one week: 604800000, one year: 31556926000
# special script :: absolute mode: $(2014/07/10), relative mode: addDay(3).addMonth(4)

environment.title = Production

# Does it enable the Framework internal debug? (true only when emergency)
framework.debug = false

# one day: 86400000, three days: 259200000, five days: 432000000, one week: 604800000, one year: 31556926000
# special script :: absolute mode: $(2014/07/10), relative mode: addDay(3).addMonth(4)

environment.title = Production

# Does it enable the Framework internal debug? (true only when emergency)
framework.debug = false

# one day: 86400000, three days: 259200000, five days: 432000000, one week: 604800000, one year: 31556926000
# special script :: absolute mode: $(2014/07/10), relative mode: addDay(3).addMonth(4)

 * @author mbechler
 *
 * <p>This interface is intended for internal use.</p>
 */
public interface BufferCache {

    /**
     * Gets a buffer from the cache or creates a new one if the cache is empty.
     *
     * @return a buffer from the cache, or a new one
     */
    byte[] getBuffer();

    /**
     * Return a buffer to the cache
     *
     * @param buf the buffer to return to the cache for reuse
     */

All replication failures are picked up by the scanner which runs at a one minute frequency, each time scanning up to a sixteenth of the namespace. Object versions marked `PENDING` or `FAILED` are re-queued for replication.