Move inner classes to upper level

Rename as follows.
- ResourceId.Discrete -> DiscreteResourceId
- ResourceId.Continuous -> ContinuousResourceId
- Resource.Discrete -> DiscreteResource
- Resource.Continuous -> ContinuousResource

Change-Id: I80e59d1eec07128743bacc582a8725bd4d5489b4
diff --git a/core/api/src/main/java/org/onosproject/net/newresource/DiscreteResource.java b/core/api/src/main/java/org/onosproject/net/newresource/DiscreteResource.java
new file mode 100644
index 0000000..9efbbd1
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/newresource/DiscreteResource.java
@@ -0,0 +1,73 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.newresource;
+
+import com.google.common.annotations.Beta;
+
+import java.util.Objects;
+
+/**
+ * Represents a resource path which specifies a resource which can be measured
+ * as a discrete unit. A VLAN ID and a MPLS label of a link are examples of the resource.
+ * <p>
+ * Note: This class is exposed to the public, but intended to be used in the resource API
+ * implementation only. It is not for resource API user.
+ * </p>
+ */
+@Beta
+// TODO: consider how to restrict the visibility
+public final class DiscreteResource extends Resource {
+    protected DiscreteResource() {
+        super();
+    }
+
+    DiscreteResource(ResourceId id) {
+        super(id);
+    }
+
+    /**
+     * The user of this methods must receive the return value as the correct type.
+     * Otherwise, this methods throws an exception.
+     *
+     * @param <T> type of the return value
+     * @return the volume of this resource
+     */
+    @SuppressWarnings("unchecked")
+    @Override
+    // TODO: consider receiving Class<T> as an argument. Which approach is convenient?
+    public <T> T volume() {
+        return (T) last();
+    }
+
+    @Override
+    public int hashCode() {
+        // the value returing from volume() is excluded due to optimization
+        return id().hashCode();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final DiscreteResource other = (DiscreteResource) obj;
+        // the value returing from volume() is excluded due to optimization
+        return Objects.equals(this.id(), other.id());
+    }
+}