*   <li>clearing weak references to unreachable referents
   *   <li>enqueuing weak references to unreachable referents in their reference queue
   * </ul>
   */
  @DoNotMock("Implement with a lambda")
  public interface FinalizationPredicate {
    boolean isDone();
  }

  /**
   * Waits until the given weak reference is cleared, invoking the garbage collector as necessary to

    }
  }

  /**
   * Cleans up the given reference and any other references already in the queue. Catches and logs
   * all throwables.
   *
   * @return true if the caller should continue to wait for more references to be added to the
   *     queue, false if the associated FinalizableReferenceQueue is no longer referenced.
   */
  private boolean cleanUp(Reference<?> firstReference) {

   *   <li>clearing weak references to unreachable referents
   *   <li>enqueuing weak references to unreachable referents in their reference queue
   * </ul>
   */
  @DoNotMock("Implement with a lambda")
  public interface FinalizationPredicate {
    boolean isDone();
  }

  /**
   * Waits until the given weak reference is cleared, invoking the garbage collector as necessary to

  }

  public void testGetIfPresent_whenNoMatchingConstant() {
    assertThat(Enums.getIfPresent(TestEnum.class, "WOMBAT")).isAbsent();
  }


  @J2ktIncompatible
  @GwtIncompatible // weak references
  @AndroidIncompatible // depends on details of GC and classloading
  public void testGetIfPresent_doesNotPreventClassUnloading() throws Exception {
    WeakReference<?> shadowLoaderReference = doTestClassUnloading();

 * predicate::test}.
 *
 * <p>This interface is now a legacy type. Use {@code java.util.function.Predicate} (or the
 * appropriate primitive specialization such as {@code IntPredicate}) instead whenever possible.
 * Otherwise, at least reduce <i>explicit</i> dependencies on this type by using lambda expressions

import com.google.errorprone.annotations.DoNotMock;

/**
 * Implemented by references that have code to run after garbage collection of their referents.
 *
 * @see FinalizableReferenceQueue
 * @author Bob Lee
 * @since 2.0
 */
@DoNotMock("Use an instance of one of the Finalizable*Reference classes")
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault

      /*
       * Using weak references here could let us release exceptions earlier, but:
       *
       * 1. On Android, querying a WeakReference blocks if the GC is doing an otherwise-concurrent
       * pass.
       *
       * 2. We would probably choose to compare exceptions using == instead of equals() (for
       * consistency with how weak references are cleared). That's a behavior change -- arguably the

 * or method references instead of classes, leaving your code easier to migrate in the future.
 *
 * <p>To use a reference of this type (say, named {@code guavaPredicate}) in a context where {@code
 * java.util.function.Predicate} is expected, use the method reference {@code
 * guavaPredicate::apply}. For the other direction, use {@code javaUtilPredicate::test}. A future

      fail("peek() should still throw NoSuchElementException after next()");
    } catch (NoSuchElementException expected) {
    }
  }


  @J2ktIncompatible // weak references, details of GC
  @GwtIncompatible // weak references
  @AndroidIncompatible // depends on details of GC
  public void testFreesNextReference() {
    Iterator<Object> itr =
        new AbstractIterator<Object>() {
          @Override

import java.util.concurrent.ConcurrentMap;
import javax.annotation.CheckForNull;

/**
 * A builder of {@link ConcurrentMap} instances that can have keys or values automatically wrapped
 * in {@linkplain WeakReference weak} references.
 *
 * <p>Usage example:
 *
 * <pre>{@code
 * ConcurrentMap<Request, Stopwatch> timers = new MapMaker()
 *     .concurrencyLevel(4)
 *     .weakKeys()
 *     .makeMap();
 * }</pre>
 *