### 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.

import com.google.common.annotations.J2ktIncompatible;
import java.util.AbstractMap.SimpleImmutableEntry;
import org.jspecify.annotations.Nullable;

/**
 * A notification of the removal of a single entry. The key and/or value may be null if they were
 * already garbage collected.
 *
 * <p>Like other {@code Entry} instances associated with {@code CacheBuilder}, this class holds

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() {}

  /**

  public void testAwait_countDownLatch() {
    CountDownLatch latch = new CountDownLatch(1);
    Object unused =
        new Object() {
          @SuppressWarnings({"removal", "Finalize"}) // b/487687332
          @Override
          protected void finalize() {
            latch.countDown();
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable

    // 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());
    }

    // 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());
    }

        classes['NewSub'].superclass = classes['NewBase']

        apiClass.compatibilityChanges >> [new JApiCompatibilityChange(JApiCompatibilityChangeType.METHOD_REMOVED_IN_SUPERCLASS)]
    }

    def "method removal can be reported if current class is first public class"() {
        given:
        apiClass.oldClass >> Optional.of(classes['OldBase'])
        apiClass.newClass >> Optional.of(classes['NewBase'])

        when:

 * the License.
 */

package com.google.common.cache;

import com.google.common.annotations.GwtCompatible;

/**
 * An object that can receive a notification when an entry is removed from a cache. The removal
 * resulting in notification could have occurred to an entry being manually removed or replaced, or
 * due to eviction resulting from timed expiration, exceeding a maximum size, or garbage collection.
 *

  /**
   * Returns the next element in the iteration, without advancing the iteration.
   *
   * <p>Calls to {@code peek()} should not change the state of the iteration, except that it
   * <i>may</i> prevent removal of the most recent element via {@link #remove()}.
   *
   * @throws NoSuchElementException if the iteration has no more elements according to {@link
   *     #hasNext()}
   */
  @ParametricNullness
  E peek();

  /*
   * 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