ValueReference<K, V> valueRef = entry.getValueReference();
      // fail on strong/computing refs
      Preconditions.checkState(valueRef instanceof Reference);
      Reference<V> ref = (Reference<V>) valueRef;
      if (ref != null) {
        ref.clear();
      }
    }
  }

  /**
   * Poke into the Cache internals to simulate garbage collection of the given key. This assumes

import com.google.common.testing.NullPointerTester;
import com.google.common.testing.SerializableTester;
import java.io.File;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.ref.WeakReference;
import java.lang.reflect.Field;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.HashSet;
import java.util.Set;
import junit.framework.TestCase;

   *   public boolean isDone() {
   *     return ref.get() == null;
   *   }
   * });
   * }</pre>
   *
   * @throws RuntimeException if timed out or interrupted while waiting
   */
  public static void awaitClear(WeakReference<?> ref) {
    awaitDone(
        new FinalizationPredicate() {
          @Override
          public boolean isDone() {
            return ref.get() == null;
          }
        });
  }

          @Override
          public Object computeNext() {
            return new Object();
          }
        };
    WeakReference<Object> ref = new WeakReference<>(itr.next());
    GcFinalization.awaitClear(ref);
  }

  public void testDefaultBehaviorOfPeekForEmptyIteration() {

    AbstractIterator<Integer> empty =
        new AbstractIterator<Integer>() {

    int iterations = 10;
    WeakReference<Object> ref = new WeakReference<>(null);
    int expectedComputations = 0;
    for (int i = 0; i < iterations; i++) {
      // The entry should get garbage collected and recomputed.
      Object oldValue = ref.get();
      if (oldValue == null) {
        expectedComputations++;
      }
      ref = new WeakReference<>(cache.getUnchecked(1));
      oldValue = null;

 * the License.
 */

package com.google.common.base;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import javax.annotation.CheckForNull;

/**
 * Weak reference with a {@code finalizeReferent()} method which a background thread invokes after

package com.google.common.base;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.internal.Finalizer;
import com.google.common.testing.GcFinalization;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
import java.util.Collections;
import junit.framework.TestCase;

package com.google.common.base;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.internal.Finalizer;
import com.google.common.testing.GcFinalization;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
import java.util.Collections;
import junit.framework.TestCase;

    assertTrue(future.isDone());
    assertTrue(future.isCancelled());
  }

  public void testAwaitClear() {
    final WeakReference<Object> ref = new WeakReference<>(new Object());
    GcFinalization.awaitClear(ref);
    assertNull(ref.get());
  }

  public void testAwaitDone_FinalizationPredicate() {
    final WeakHashMap<Object, Object> map = new WeakHashMap<>();
    map.put(new Object(), Boolean.TRUE);

    assertTrue(future.isDone());
    assertTrue(future.isCancelled());
  }

  public void testAwaitClear() {
    final WeakReference<Object> ref = new WeakReference<>(new Object());
    GcFinalization.awaitClear(ref);
    assertNull(ref.get());
  }

  public void testAwaitDone_FinalizationPredicate() {
    final WeakHashMap<Object, Object> map = new WeakHashMap<>();
    map.put(new Object(), Boolean.TRUE);