Pull out inner-classes from Criteria to be independent classes

Make constructors of sub-types of Criterion package private for
limiting instantiation only from static factory methods in Criteria

Change-Id: I1fb1e9d003288a778a49e758549a92b66bf3cfdf
diff --git a/core/api/src/main/java/org/onosproject/net/flow/criteria/EthCriterion.java b/core/api/src/main/java/org/onosproject/net/flow/criteria/EthCriterion.java
new file mode 100644
index 0000000..b73e58b
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/flow/criteria/EthCriterion.java
@@ -0,0 +1,80 @@
+/*
+ * Copyright 2015 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.flow.criteria;
+
+import org.onlab.packet.MacAddress;
+
+import java.util.Objects;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * Implementation of MAC address criterion.
+ */
+public final class EthCriterion implements Criterion {
+    private final MacAddress mac;
+    private final Type type;
+
+    /**
+     * Constructor.
+     *
+     * @param mac the source or destination MAC address to match
+     * @param type the match type. Should be either Type.ETH_DST or
+     * Type.ETH_SRC
+     */
+    EthCriterion(MacAddress mac, Type type) {
+        this.mac = mac;
+        this.type = type;
+    }
+
+    @Override
+    public Type type() {
+        return this.type;
+    }
+
+    /**
+     * Gets the MAC address to match.
+     *
+     * @return the MAC address to match
+     */
+    public MacAddress mac() {
+        return this.mac;
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(type().toString())
+                .add("mac", mac).toString();
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, mac);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof EthCriterion) {
+            EthCriterion that = (EthCriterion) obj;
+            return Objects.equals(mac, that.mac) &&
+                    Objects.equals(type, that.type);
+        }
+        return false;
+    }
+}