Use lower bound wildcard for API to be more flexible

Change-Id: Ia6bcec5afb2e872b55bae4bbd9139ad35ce01284

@@ -43,7 +43,7 @@ public interface ResourceAdminService {
      * @return true if registration is successfully done, false otherwise. Registration
      * succeeds when each resource is not registered or unallocated.
      */
-    boolean register(List<Resource> resources);
+    boolean register(List<? extends Resource> resources);
 
     /**
      * Unregisters the specified resources.
@@ -63,5 +63,5 @@ public interface ResourceAdminService {
      * @return true if unregistration is successfully done, false otherwise. Unregistration
      * succeeds when each resource is not registered or unallocated.
      */
-    boolean unregister(List<ResourceId> ids);
+    boolean unregister(List<? extends ResourceId> ids);
 }

@@ -66,7 +66,7 @@ public interface ResourceService extends ListenerService<ResourceEvent, Resource
      * @param resources resources to be allocated
      * @return non-empty list of allocation information if succeeded, otherwise empty list
      */
-    List<ResourceAllocation> allocate(ResourceConsumer consumer, List<Resource> resources);
+    List<ResourceAllocation> allocate(ResourceConsumer consumer, List<? extends Resource> resources);
 
     /**
      * Transactionally allocates the specified resources to the specified user.

@@ -37,7 +37,7 @@ public interface ResourceStore extends Store<ResourceEvent, ResourceStoreDelegat
      * @param resources resources to be registered
      * @return true if the registration succeeds, false otherwise
      */
-    boolean register(List<Resource> resources);
+    boolean register(List<? extends Resource> resources);
 
     /**
      * Unregisters the resources in transactional way.
@@ -48,7 +48,7 @@ public interface ResourceStore extends Store<ResourceEvent, ResourceStoreDelegat
      * @param ids resources to be unregistered
      * @return true if the registration succeeds, false otherwise
      */
-    boolean unregister(List<ResourceId> ids);
+    boolean unregister(List<? extends ResourceId> ids);
 
     /**
      * Allocates the specified resources to the specified consumer in transactional way.
@@ -60,7 +60,7 @@ public interface ResourceStore extends Store<ResourceEvent, ResourceStoreDelegat
      * @param consumer resource consumer which the resources are allocated to
      * @return true if the allocation succeeds, false otherwise.
      */
-    boolean allocate(List<Resource> resources, ResourceConsumer consumer);
+    boolean allocate(List<? extends Resource> resources, ResourceConsumer consumer);
 
     /**
      * Releases the specified resources allocated to the specified corresponding consumers

@@ -80,7 +80,7 @@ public final class ResourceManager extends AbstractListenerManager<ResourceEvent
 
     @Override
     public List<ResourceAllocation> allocate(ResourceConsumer consumer,
-                                             List<Resource> resources) {
+                                             List<? extends Resource> resources) {
         checkNotNull(consumer);
         checkNotNull(resources);
 
@@ -171,14 +171,14 @@ public final class ResourceManager extends AbstractListenerManager<ResourceEvent
     }
 
     @Override
-    public boolean register(List<Resource> resources) {
+    public boolean register(List<? extends Resource> resources) {
         checkNotNull(resources);
 
         return store.register(resources);
     }
 
     @Override
-    public boolean unregister(List<ResourceId> ids) {
+    public boolean unregister(List<? extends ResourceId> ids) {
         checkNotNull(ids);
 
         return store.unregister(ids);

@@ -44,7 +44,7 @@ class MockResourceService implements ResourceService {
     private final Map<Resource, ResourceConsumer> assignment = new HashMap<>();
 
     @Override
-    public List<ResourceAllocation> allocate(ResourceConsumer consumer, List<Resource> resources) {
+    public List<ResourceAllocation> allocate(ResourceConsumer consumer, List<? extends Resource> resources) {
         assignment.putAll(
                 resources.stream().collect(Collectors.toMap(x -> x, x -> consumer))
         );

@@ -151,7 +151,7 @@ public class ConsistentResourceStore extends AbstractStore<ResourceEvent, Resour
     }
 
     @Override
-    public boolean register(List<Resource> resources) {
+    public boolean register(List<? extends Resource> resources) {
         checkNotNull(resources);
         if (log.isTraceEnabled()) {
             resources.forEach(r -> log.trace("registering {}", r));
@@ -190,7 +190,7 @@ public class ConsistentResourceStore extends AbstractStore<ResourceEvent, Resour
     }
 
     @Override
-    public boolean unregister(List<ResourceId> ids) {
+    public boolean unregister(List<? extends ResourceId> ids) {
         checkNotNull(ids);
 
         TransactionContext tx = service.transactionContextBuilder().build();
@@ -254,7 +254,7 @@ public class ConsistentResourceStore extends AbstractStore<ResourceEvent, Resour
     }
 
     @Override
-    public boolean allocate(List<Resource> resources, ResourceConsumer consumer) {
+    public boolean allocate(List<? extends Resource> resources, ResourceConsumer consumer) {
         checkNotNull(resources);
         checkNotNull(consumer);