Pull up components() method as an abstract method

Change-Id: I80aecb74958b697fb18336bbe39853dd5cb67578

@@ -45,6 +45,7 @@ public final class ContinuousResourceId extends ResourceId {
         this.name = "";
     }
 
+    @Override
     ImmutableList<Object> components() {
         return components;
     }

@@ -42,6 +42,7 @@ public final class DiscreteResourceId extends ResourceId {
         this.components = ImmutableList.of();
     }
 
+    @Override
     ImmutableList<Object> components() {
         return components;
     }

@@ -16,6 +16,7 @@
 package org.onosproject.net.newresource;
 
 import com.google.common.annotations.Beta;
+import com.google.common.collect.ImmutableList;
 
 import java.util.Optional;
 
@@ -27,6 +28,8 @@ import java.util.Optional;
 public abstract class ResourceId {
     static final DiscreteResourceId ROOT = new DiscreteResourceId();
 
+    abstract ImmutableList<Object> components();
+
     /**
      * Returns the parent resource ID of this instance.
      *