### 3.1 Automatic removal of non current objects versions

A non-current object version is a version which is not the latest for a given object. It is possible to set up an automatic removal of non-current versions when a version becomes older than a given number of days.

  public void testAwait_countDownLatch() {
    CountDownLatch latch = new CountDownLatch(1);
    Object unused =
        new Object() {
          @SuppressWarnings({"removal", "Finalize"}) // b/260137033
          @Override
          protected void finalize() {
            latch.countDown();
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable

   * as necessary to try to ensure that this will happen.
   *
   * @throws RuntimeException if timed out or interrupted while waiting
   */
  @SuppressWarnings("removal") // b/260137033
  public static void awaitDone(Future<?> future) {
    if (future.isDone()) {
      return;
    }
    long timeoutSeconds = timeoutSeconds();

    // other operations, the cache and the removal queue won't change from this point on.

    // Verify that each received removal notification was valid
    for (RemovalNotification<String, String> notification : removalListener) {
      assertWithMessage("Invalid removal notification")
          .that(notification.getValue())
          .isEqualTo(notification.getKey());
    }

   * as necessary to try to ensure that this will happen.
   *
   * @throws RuntimeException if timed out or interrupted while waiting
   */
  @SuppressWarnings("removal") // b/260137033
  public static void awaitDone(Future<?> future) {
    if (future.isDone()) {
      return;
    }
    long timeoutSeconds = timeoutSeconds();

  /*
   * The ConcurrentHashMultiset's atomic operations are implemented primarily in terms of
   * AtomicInteger's atomic operations, with some help from ConcurrentMap's atomic operations on
   * creation and removal (including automatic removal of zeroes). If the modification of an
   * AtomicInteger results in zero, we compareAndSet the value to zero; if that succeeds, we remove

  public void testAwait_countDownLatch() {
    CountDownLatch latch = new CountDownLatch(1);
    Object unused =
        new Object() {
          @SuppressWarnings({"removal", "Finalize"}) // b/260137033
          @Override
          protected void finalize() {
            latch.countDown();
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable

 * <ul>
 *   <li><strong>Child GroupId Removal</strong>: Removes child {@code <groupId>} when it matches parent groupId</li>
 *   <li><strong>Child Version Removal</strong>: Removes child {@code <version>} when it matches parent version</li>
 * </ul>
 *
 * <h4>Full Inference for 4.1.0+ Models</h4>
 * <ul>
 *   <li><strong>ModelVersion Removal</strong>: Removes {@code <modelVersion>} element (inference enabled)</li>

  int generateInt() {
    return freshness.get();
  }

  @SuppressWarnings("removal") // b/321209431 -- maybe just use valueOf here?
  @Generates
  Integer generateInteger() {
    return new Integer(generateInt());
  }

  @Generates
  long generateLong() {
    return generateInt();
  }

  @SuppressWarnings("removal") // b/321209431 -- maybe just use valueOf here?
  @Generates
  Long generateLongObject() {

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtIncompatible;
import java.util.concurrent.Executor;

/**
 * A collection of common removal listeners.
 *
 * @author Charles Fry
 * @since 10.0
 */
@GwtIncompatible
public final class RemovalListeners {

  private RemovalListeners() {}

  /**