*/
    WILL_CREATE_VALUE_AND_CLOSER,
  }

  private static final class FinalizableReference
      extends FinalizablePhantomReference<ClosingFuture<?>> {
    static final FinalizableReferenceQueue referenceQueue = new FinalizableReferenceQueue();
    static final Set<FinalizableReference> references = newConcurrentHashSet();

    static void register(ClosingFuture<?> future) {

import com.google.common.util.concurrent.SettableFuture;
import com.google.common.util.concurrent.UncheckedExecutionException;
import java.io.Serializable;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import com.google.common.util.concurrent.SettableFuture;
import com.google.common.util.concurrent.UncheckedExecutionException;
import java.io.Serializable;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;