Use more concrete type for return value

Same resources are not allowed for a parent and Set is more suitable than
Collection

Change-Id: Ib45179819d81376678bf8949864b12b5bd721085

@@ -22,7 +22,6 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.Collections;
 
 import org.apache.karaf.shell.commands.Argument;
@@ -102,7 +101,7 @@ public class ResourcesCommand extends AbstractShellCommand {
 
     private void printResource(Resource resource, int level) {
         // TODO add an option to show only available resource
-        Collection<Resource> children = resourceService.getRegisteredResources(resource);
+        Set<Resource> children = resourceService.getRegisteredResources(resource);
 
         if (resource.equals(Resource.ROOT)) {
             print("ROOT");

@@ -23,6 +23,7 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
+import java.util.Set;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -162,7 +163,7 @@ public interface ResourceService extends ListenerService<ResourceEvent, Resource
      * @return available resources under the specified resource
      */
     // TODO: need to change the argument type to ResourceId or ResourceId.Discrete
-    Collection<Resource> getAvailableResources(Resource parent);
+    Set<Resource> getAvailableResources(Resource parent);
 
     /**
      * Returns resources registered under the specified resource.
@@ -171,7 +172,7 @@ public interface ResourceService extends ListenerService<ResourceEvent, Resource
      * @return registered resources under the specified resource
      */
     // TODO: need to change the argument type to ResourceId or ResourceId.Discrete
-    Collection<Resource> getRegisteredResources(Resource parent);
+    Set<Resource> getRegisteredResources(Resource parent);
 
 
     /**

@@ -20,6 +20,7 @@ import org.onosproject.store.Store;
 
 import java.util.Collection;
 import java.util.List;
+import java.util.Set;
 
 /**
  * Service for storing resource and consumer information.
@@ -104,13 +105,13 @@ public interface ResourceStore extends Store<ResourceEvent, ResourceStoreDelegat
     Collection<Resource> getResources(ResourceConsumer consumer);
 
     /**
-     * Returns a collection of the child resources of the specified parent.
+     * Returns a set of the child resources of the specified parent.
      *
      * @param parent parent of the resource to be returned
-     * @return a collection of the child resources of the specified resource
+     * @return a set of the child resources of the specified resource
      */
     // TODO: need to change the argument type to ResourceId or ResourceId.Discrete
-    Collection<Resource> getChildResources(Resource parent);
+    Set<Resource> getChildResources(Resource parent);
 
     /**
      * Returns a collection of the resources which are children of the specified parent and

@@ -38,6 +38,7 @@ import org.slf4j.Logger;
 
 import java.util.Collection;
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -147,18 +148,18 @@ public final class ResourceManager extends AbstractListenerManager<ResourceEvent
     }
 
     @Override
-    public Collection<Resource> getAvailableResources(Resource parent) {
+    public Set<Resource> getAvailableResources(Resource parent) {
         checkNotNull(parent);
 
-        Collection<Resource> children = store.getChildResources(parent);
+        Set<Resource> children = store.getChildResources(parent);
         return children.stream()
                 // We access store twice in this method, then the store may be updated by others
                 .filter(store::isAvailable)
-                .collect(Collectors.toList());
+                .collect(Collectors.toSet());
     }
 
     @Override
-    public Collection<Resource> getRegisteredResources(Resource parent) {
+    public Set<Resource> getRegisteredResources(Resource parent) {
         checkNotNull(parent);
 
         return store.getChildResources(parent);

@@ -16,6 +16,7 @@
 package org.onosproject.net.intent.impl.compiler;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import org.onlab.packet.MplsLabel;
 import org.onlab.packet.VlanId;
 import org.onosproject.net.newresource.ResourceAllocation;
@@ -30,6 +31,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 class MockResourceService implements ResourceService {
@@ -92,16 +94,16 @@ class MockResourceService implements ResourceService {
     }
 
     @Override
-    public Collection<Resource> getAvailableResources(Resource parent) {
+    public Set<Resource> getAvailableResources(Resource parent) {
 
         Collection<Resource> resources = new HashSet<Resource>();
         resources.add(parent.child(VlanId.vlanId((short) 10)));
         resources.add(parent.child(MplsLabel.mplsLabel(10)));
-        return ImmutableList.copyOf(resources);
+        return ImmutableSet.copyOf(resources);
     }
 
     @Override
-    public Collection<Resource> getRegisteredResources(Resource parent) {
+    public Set<Resource> getRegisteredResources(Resource parent) {
         return getAvailableResources(parent);
     }
 

@@ -17,6 +17,7 @@ package org.onosproject.store.newresource.impl;
 
 import com.google.common.annotations.Beta;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Maps;
 import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
@@ -389,16 +390,16 @@ public class ConsistentResourceStore extends AbstractStore<ResourceEvent, Resour
     }
 
     @Override
-    public Collection<Resource> getChildResources(Resource parent) {
+    public Set<Resource> getChildResources(Resource parent) {
         checkNotNull(parent);
         if (!(parent instanceof DiscreteResource)) {
             // only Discrete resource can have child resource
-            return ImmutableList.of();
+            return ImmutableSet.of();
         }
 
         Versioned<Set<Resource>> children = childMap.get((DiscreteResource) parent);
         if (children == null) {
-            return ImmutableList.of();
+            return ImmutableSet.of();
         }
 
         return children.value();