}

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  /*
   * absent = ZERO isn't required, since unmodList.add() must
   * throw regardless, but it keeps the method name accurate.
   */
  public void testAdd_unsupportedPresent() {
    assertThrows(UnsupportedOperationException.class, () -> getList().add(e0()));
  }

  @CollectionFeature.Require(value = {SUPPORTS_ADD, ALLOWS_NULL_VALUES})

  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  /*
   * absent = ZERO isn't required, since unmodList.add() must
   * throw regardless, but it keeps the method name accurate.
   */
  public void testAdd_unsupportedPresent() {
    assertThrows(UnsupportedOperationException.class, () -> getList().add(e0()));
  }

  @CollectionFeature.Require(value = {SUPPORTS_ADD, ALLOWS_NULL_VALUES})

  }

  @ListFeature.Require(absent = SUPPORTS_ADD_WITH_INDEX)
  @CollectionSize.Require(absent = ZERO)
  /*
   * absent = ZERO isn't required, since unmodList.add() must
   * throw regardless, but it keeps the method name accurate.
   */
  public void testAddAtIndex_unsupportedPresent() {
    assertThrows(UnsupportedOperationException.class, () -> getList().add(0, e0()));
    expectUnchanged();
  }

  public void decrement() {
    add(-1L);
  }

  /**
   * Returns the current sum. The returned value is NOT an atomic snapshot; invocation in
   * the absence of concurrent updates returns an accurate result, but concurrent updates that occur
   * while the sum is being calculated might not be incorporated.
   *
   * @return the sum
   */
  @Override
  public long sum() {
    long sum = base;

Do not make a parameter `@Nullable` just to check and throw a `NullPointerException` when it is `null`. 

## Consequences

* Classes are forced to have consistent nullability annotations.
* IDE warnings become more accurate, reducing warnings fatigue.
* Public API nullability annotations become closer to reality.
* Java compilation of Gradle code suffers from small performance penalty (up to 10%).

  }

  @ListFeature.Require(absent = SUPPORTS_ADD_WITH_INDEX)
  @CollectionSize.Require(absent = ZERO)
  /*
   * absent = ZERO isn't required, since unmodList.add() must
   * throw regardless, but it keeps the method name accurate.
   */
  public void testAddAtIndex_unsupportedPresent() {
    assertThrows(UnsupportedOperationException.class, () -> getList().add(0, e0()));
    expectUnchanged();
  }

 * Stopwatch} requires object allocation and additional method calls, which can reduce the accuracy
 * of the elapsed times reported. {@code Stopwatch} is still suitable for logging and metrics where
 * reasonably accurate values are sufficient. If the uncommon case that you need to maximize
 * accuracy, use {@code System.nanoTime()} directly instead.
 *
 * <p>Basic usage:
 *
 * {@snippet :

  }

  public void testServiceStartupTimes_selfStartingServices() {
    // This tests to ensure that:
    // 1. service times are accurate when the service is started by the manager
    // 2. service times are recorded when the service is not started by the manager (but they may
    // not be accurate).
    Service b =
        new NoOpDelayedService(353) {
          @Override
          protected void doStart() {

        };
      }
    }

    private static String getUsername() {
      /*
       * https://github.com/google/guava/issues/6634: ProcessHandle has more accurate information,
       * but that class isn't available under all environments that we support. We use it if
       * available and fall back if not.
       */

     * close *estimate* of the actual number of bits set. It's not possible to do better than an
     * estimate without locking. Note that the number, if not exactly accurate, is *always*
     * underestimating, never overestimating.
     */
    long bitCount() {
      return bitCount.sum();
    }

    LockFreeBitArray copy() {