ONOS-3749: Show Flow ID and group ID in the flow table as hex values.

Change-Id: If98e0d76876ada2fa1c8d01a1b89230d1919f6c5
diff --git a/core/api/src/main/java/org/onosproject/ui/table/cell/HexLongFormatter.java b/core/api/src/main/java/org/onosproject/ui/table/cell/HexLongFormatter.java
new file mode 100644
index 0000000..9155efe
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/ui/table/cell/HexLongFormatter.java
@@ -0,0 +1,38 @@
+/*
+ *  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.ui.table.cell;
+
+import org.onosproject.ui.table.CellFormatter;
+
+/**
+ * Formats long values as hex strings with a "0x" prefix.
+ */
+public final class HexLongFormatter extends AbstractCellFormatter {
+
+    // non-instantiable
+    private HexLongFormatter() { }
+
+    @Override
+    protected String nonNullFormat(Object value) {
+        return "0x" + Long.toHexString((Long) value);
+    }
+
+    /**
+     * An instance of this class.
+     */
+    public static final CellFormatter INSTANCE = new HexLongFormatter();
+}