Merge "Refactor: improve null safety by using empty list instead of null"

@@ -23,6 +23,7 @@ import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -61,7 +62,7 @@ public abstract class ConnectivityIntent extends Intent {
                                  Collection<NetworkResource> resources,
                                  TrafficSelector selector,
                                  TrafficTreatment treatment) {
-        this(id, appId, resources, selector, treatment, null);
+        this(id, appId, resources, selector, treatment, Collections.emptyList());
     }
 
     /**
@@ -87,7 +88,7 @@ public abstract class ConnectivityIntent extends Intent {
         super(id, appId, resources);
         this.selector = checkNotNull(selector);
         this.treatment = checkNotNull(treatment);
-        this.constraints = constraints;
+        this.constraints = checkNotNull(constraints);
     }
 
     /**
@@ -97,7 +98,7 @@ public abstract class ConnectivityIntent extends Intent {
         super();
         this.selector = null;
         this.treatment = null;
-        this.constraints = null;
+        this.constraints = Collections.emptyList();
     }
 
     /**

@@ -21,6 +21,7 @@ import org.onlab.onos.net.HostId;
 import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
 
+import java.util.Collections;
 import java.util.List;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -46,7 +47,7 @@ public final class HostToHostIntent extends ConnectivityIntent {
     public HostToHostIntent(ApplicationId appId, HostId one, HostId two,
                             TrafficSelector selector,
                             TrafficTreatment treatment) {
-        this(appId, one, two, selector, treatment, null);
+        this(appId, one, two, selector, treatment, Collections.emptyList());
     }
 
     /**

@@ -22,6 +22,7 @@ import org.onlab.onos.net.Link;
 import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
@@ -51,7 +52,7 @@ public final class LinkCollectionIntent extends ConnectivityIntent {
                                 TrafficTreatment treatment,
                                 Set<Link> links,
                                 ConnectPoint egressPoint) {
-        this(appId, selector , treatment, links, egressPoint, null);
+        this(appId, selector , treatment, links, egressPoint, Collections.emptyList());
     }
 
     /**

@@ -22,6 +22,7 @@ import org.onlab.onos.net.ConnectPoint;
 import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
@@ -55,14 +56,7 @@ public final class MultiPointToSinglePointIntent extends ConnectivityIntent {
                                          TrafficTreatment treatment,
                                          Set<ConnectPoint> ingressPoints,
                                          ConnectPoint egressPoint) {
-        super(id(MultiPointToSinglePointIntent.class, selector, treatment,
-                 ingressPoints, egressPoint), appId, null, selector, treatment);
-
-        checkNotNull(ingressPoints);
-        checkArgument(!ingressPoints.isEmpty(), "Ingress point set cannot be empty");
-
-        this.ingressPoints = Sets.newHashSet(ingressPoints);
-        this.egressPoint = checkNotNull(egressPoint);
+        this(appId, selector, treatment, ingressPoints, egressPoint, Collections.emptyList());
     }
 
     /**

@@ -15,6 +15,7 @@
  */
 package org.onlab.onos.net.intent;
 
+import java.util.Collections;
 import java.util.List;
 
 import com.google.common.base.MoreObjects;
@@ -42,9 +43,7 @@ public class PathIntent extends ConnectivityIntent {
      */
     public PathIntent(ApplicationId appId, TrafficSelector selector,
                       TrafficTreatment treatment, Path path) {
-        super(id(PathIntent.class, selector, treatment, path), appId,
-              resources(path.links()), selector, treatment);
-        this.path = path;
+        this(appId, selector, treatment, path, Collections.emptyList());
     }
 
     /**