int i = 0;
      for (Object e : elements) {
        array[i++] = (Integer) e;
      }
      return create(array);
    }

    /**
     * Creates a new collection containing the given elements; implement this method instead of
     * {@link #create(Object...)}.
     */
    protected abstract List<Integer> create(Integer[] elements);

    @Override
    public Integer[] createArray(int length) {

      int i = 0;
      for (Object e : elements) {
        array[i++] = (Byte) e;
      }
      return create(array);
    }

    /**
     * Creates a new collection containing the given elements; implement this method instead of
     * {@link #create(Object...)}.
     */
    protected abstract List<Byte> create(Byte[] elements);

    @Override
    public Byte[] createArray(int length) {

 * and performant but introduces some testing difficulties. This test exercises the two fallback
 * strategies.
 *
 * <ul>
 *   <li>SafeAtomicHelper: uses Atomic FieldsUpdaters to implement synchronization
 *   <li>SynchronizedHelper: uses {@code synchronized} blocks for synchronization
 * </ul>
 *
 * To force selection of our fallback strategies we load {@link AggregateFutureState} (and all of

      int i = 0;
      for (Object e : elements) {
        array[i++] = (Double) e;
      }
      return create(array);
    }

    /**
     * Creates a new collection containing the given elements; implement this method instead of
     * {@link #create(Object...)}.
     */
    protected abstract List<Double> create(Double[] elements);

    @Override
    public Double[] createArray(int length) {

      short i = 0;
      for (Object e : elements) {
        array[i++] = (Short) e;
      }
      return create(array);
    }

    /**
     * Creates a new collection containing the given elements; implement this method instead of
     * {@link #create(Object...)}.
     */
    protected abstract List<Short> create(Short[] elements);

    @Override
    public Short[] createArray(int length) {

    singleCallListener.waitForCall();

    assertTrue(singleCallListener.wasCalled());
    assertTrue(listenableFuture.isDone());
  }

  /** A Future that doesn't implement ListenableFuture, useful for testing listenInPoolThread. */
  private static final class NonListenableSettableFuture<V> extends ForwardingFuture<V> {
    static <V> NonListenableSettableFuture<V> create() {

import java.lang.reflect.Method;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.CheckForNull;

/**
 * Thread that finalizes referents. All references should implement {@code
 * com.google.common.base.FinalizableReference}.
 *
 * <p>While this class is public, we consider it to be *internal* and not part of our published API.

import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * This class provides a skeletal implementation of the {@code Iterator} interface, to make this
 * interface easier to implement for certain types of data sources.
 *
 * <p>{@code Iterator} requires its implementations to support querying the end-of-data status
 * without changing the iterator's state, using the {@link #hasNext} method. But many data sources,

public final class JdkFutureAdapters {
  /**
   * Assigns a thread to the given {@link Future} to provide {@link ListenableFuture} functionality.
   *
   * <p><b>Warning:</b> If the input future does not already implement {@code ListenableFuture}, the
   * returned future will emulate {@link ListenableFuture#addListener} by taking a thread from an
   * internal, unbounded pool at the first call to {@code addListener} and holding it until the

    int i = 0;
    for (Object e : elements) {
      array[i++] = (String) e;
    }
    return create(array);
  }

  /**
   * Creates a new collection containing the given elements; implement this method instead of {@link
   * #create(Object...)}.
   */
  protected abstract List<String> create(String[] elements);

  @Override
  public String[] createArray(int length) {
    return new String[length];