1 files changed, 61 insertions, 0 deletions
diff --git a/framework/src/onos/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellComparator.java b/framework/src/onos/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellComparator.java
new file mode 100644
index 00000000..6113fc3f
--- /dev/null
+++ b/framework/src/onos/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellComparator.java
@@ -0,0 +1,61 @@
+/*
+ * 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.ui.table.cell;
+
+import org.onosproject.ui.table.CellComparator;
+
+/**
+ * Base implementation of a {@link CellComparator}. This class takes care
+ * of dealing with null inputs; subclasses should implement their comparison
+ * knowing that both inputs are guaranteed to be non-null.
+ */
+public abstract class AbstractCellComparator implements CellComparator {
+
+    @Override
+    public int compare(Object o1, Object o2) {
+        if (o1 == null && o2 == null) {
+            return 0;       // o1 == o2
+        }
+        if (o1 == null) {
+            return -1;      // o1 < o2
+        }
+        if (o2 == null) {
+            return 1;       // o1 > o2
+        }
+        return nonNullCompare(o1, o2);
+    }
+
+    /**
+     * Compares its two arguments for order.  Returns a negative integer,
+     * zero, or a positive integer as the first argument is less than, equal
+     * to, or greater than the second.<p>
+     *
+     * Note that both objects are guaranteed to be non-null.
+     *
+     * @see java.util.Comparator#compare(Object, Object)
+     *
+     * @param o1 the first object to be compared.
+     * @param o2 the second object to be compared.
+     * @return a negative integer, zero, or a positive integer as the
+     *         first argument is less than, equal to, or greater than the
+     *         second.
+     * @throws ClassCastException if the arguments' types prevent them from
+     *         being compared by this comparator.
+     */
+    protected abstract int nonNullCompare(Object o1, Object o2);
+}