-import akka.actor.ActorRef;
-import akka.actor.ActorSelection;
-import akka.actor.Cancellable;
-import akka.actor.PoisonPill;
-import akka.actor.Props;
-import akka.event.Logging;
-import akka.event.LoggingAdapter;
-import akka.japi.Creator;
-import akka.persistence.RecoveryFailure;
-import akka.serialization.Serialization;
-import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Optional;
-import com.google.common.base.Preconditions;
-import com.google.common.collect.Lists;
-import com.google.common.util.concurrent.FutureCallback;
-import com.google.common.util.concurrent.Futures;
-import com.google.common.util.concurrent.ListenableFuture;
-import com.google.protobuf.ByteString;
-import com.google.protobuf.InvalidProtocolBufferException;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.Nonnull;