Use JDK's Optional instead of Guava's Optional

Change-Id: Ia37b2977ede215363374e292b5565f007f1d6483

@@ -15,15 +15,14 @@
  */
 package org.onosproject.store.flow;
 
-import static com.google.common.base.Preconditions.checkNotNull;
+import com.google.common.base.Objects;
+import org.onosproject.cluster.NodeId;
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
 
-import org.onosproject.cluster.NodeId;
-
-import com.google.common.base.Objects;
-import com.google.common.base.Optional;
+import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
  * Class to represent placement information about Master/Backup copy.
@@ -40,7 +39,7 @@ public final class ReplicaInfo {
      * @param backups list of NodeId, where backup copies should be placed
      */
     public ReplicaInfo(NodeId master, List<NodeId> backups) {
-        this.master = Optional.fromNullable(master);
+        this.master = Optional.ofNullable(master);
         this.backups = checkNotNull(backups);
     }
 
@@ -79,7 +78,7 @@ public final class ReplicaInfo {
 
     // for Serializer
     private ReplicaInfo() {
-        this.master = Optional.absent();
+        this.master = Optional.empty();
         this.backups = Collections.emptyList();
     }
 }

@@ -15,7 +15,6 @@
  */
 package org.onosproject.store.flow.impl;
 
-import com.google.common.base.Optional;
 import com.google.common.collect.Maps;
 import org.junit.After;
 import org.junit.Before;
@@ -38,6 +37,7 @@ import org.onosproject.store.flow.ReplicaInfoService;
 import java.util.Collections;
 import java.util.LinkedList;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
@@ -89,7 +89,7 @@ public class ReplicaInfoManagerTest {
         assertEquals(Collections.emptyList(), info1.backups());
 
         ReplicaInfo info2 = service.getReplicaInfoFor(DID2);
-        assertEquals("There's no master", Optional.absent(), info2.master());
+        assertEquals("There's no master", Optional.empty(), info2.master());
         // backups are always empty for now
         assertEquals(Collections.emptyList(), info2.backups());
     }
@@ -116,7 +116,7 @@ public class ReplicaInfoManagerTest {
         MasterNodeCheck(CountDownLatch latch, DeviceId did,
                         NodeId nid) {
             this.latch = latch;
-            this.expectedMaster = Optional.fromNullable(nid);
+            this.expectedMaster = Optional.ofNullable(nid);
             this.expectedDevice = did;
         }