adding EthType to secure handling ether types

this will also pretty print ethertypes in flow output

Change-Id: I9363070ad308f3c756735e29b3992c500e503636
diff --git a/core/api/src/main/java/org/onosproject/net/flow/criteria/Criteria.java b/core/api/src/main/java/org/onosproject/net/flow/criteria/Criteria.java
index a163cea..f285496 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/criteria/Criteria.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/criteria/Criteria.java
@@ -15,6 +15,7 @@
  */
 package org.onosproject.net.flow.criteria;
 
+import org.onlab.packet.EthType;
 import org.onosproject.net.IndexedLambda;
 import org.onosproject.net.Lambda;
 import org.onosproject.net.OchSignal;
@@ -101,6 +102,16 @@
     }
 
     /**
+     * Creates a match on ETH_TYPE field using the specified value.
+     *
+     * @param ethType eth type value
+     * @return match criterion
+     */
+    public static Criterion matchEthType(EthType ethType) {
+        return new EthTypeCriterion(ethType);
+    }
+
+    /**
      * Creates a match on VLAN ID field using the specified value.
      *
      * @param vlanId vlan id value