GUI -- added getAsString() to TableModel.Row.
- Moved cell-related classes to new package.
- Created base classes for cell comparator and formatter.
- Created IntComparator and HexFormatter.

Change-Id: I3861bf3e0ca738a2d6eab9c70174db53f22960f8
diff --git a/core/api/src/main/java/org/onosproject/ui/table/CellFormatter.java b/core/api/src/main/java/org/onosproject/ui/table/CellFormatter.java
index 49a316d..854ac27 100644
--- a/core/api/src/main/java/org/onosproject/ui/table/CellFormatter.java
+++ b/core/api/src/main/java/org/onosproject/ui/table/CellFormatter.java
@@ -24,7 +24,8 @@
 
     /**
      * Formats the specified value into a string appropriate for displaying
-     * in a table cell.
+     * in a table cell. Note that null values are acceptable, and will result
+     * in the empty string.
      *
      * @param value the value
      * @return the formatted string
diff --git a/core/api/src/main/java/org/onosproject/ui/table/TableModel.java b/core/api/src/main/java/org/onosproject/ui/table/TableModel.java
index 7fb336e..2c3ffc5 100644
--- a/core/api/src/main/java/org/onosproject/ui/table/TableModel.java
+++ b/core/api/src/main/java/org/onosproject/ui/table/TableModel.java
@@ -17,6 +17,8 @@
 package org.onosproject.ui.table;
 
 import com.google.common.collect.Sets;
+import org.onosproject.ui.table.cell.DefaultCellComparator;
+import org.onosproject.ui.table.cell.DefaultCellFormatter;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -254,6 +256,17 @@
         public Object get(String columnId) {
             return cells.get(columnId);
         }
+
+        /**
+         * Returns the value of the cell as a string, using the
+         * formatter appropriate for the column.
+         *
+         * @param columnId column identifier
+         * @return formatted cell value
+         */
+        public String getAsString(String columnId) {
+            return getFormatter(columnId).format(get(columnId));
+        }
     }
 
     private static final String DESC = "desc";
diff --git a/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellComparator.java b/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellComparator.java
new file mode 100644
index 0000000..6113fc3
--- /dev/null
+++ b/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);
+}
diff --git a/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellFormatter.java b/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellFormatter.java
new file mode 100644
index 0000000..33ce2ab
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/ui/table/cell/AbstractCellFormatter.java
@@ -0,0 +1,42 @@
+/*
+ * 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.CellFormatter;
+
+/**
+ * Base implementation of a {@link CellFormatter}. This class takes care of
+ * dealing with null inputs; subclasses should implement their format method
+ * knowing that the input is guaranteed to be non-null.
+ */
+public abstract class AbstractCellFormatter implements CellFormatter {
+
+    @Override
+    public String format(Object value) {
+        return value == null ? "" : nonNullFormat(value);
+    }
+
+    /**
+     * Formats the specified value into a string appropriate for displaying
+     * in a table cell. Note that value is guaranteed to be non-null.
+     *
+     * @param value the value
+     * @return the formatted string
+     */
+    protected abstract String nonNullFormat(Object value);
+}
diff --git a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellComparator.java b/core/api/src/main/java/org/onosproject/ui/table/cell/DefaultCellComparator.java
similarity index 71%
rename from core/api/src/main/java/org/onosproject/ui/table/DefaultCellComparator.java
rename to core/api/src/main/java/org/onosproject/ui/table/cell/DefaultCellComparator.java
index c27be61..7846f89 100644
--- a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellComparator.java
+++ b/core/api/src/main/java/org/onosproject/ui/table/cell/DefaultCellComparator.java
@@ -15,7 +15,7 @@
  *
  */
 
-package org.onosproject.ui.table;
+package org.onosproject.ui.table.cell;
 
 /**
  * A default cell comparator. Implements a lexicographical compare function
@@ -23,18 +23,9 @@
  * compares the resulting strings. Note that null values are acceptable and
  * are considered "smaller" than any non-null value.
  */
-public class DefaultCellComparator implements CellComparator {
+public class DefaultCellComparator extends AbstractCellComparator {
     @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
-        }
+    protected int nonNullCompare(Object o1, Object o2) {
         return o1.toString().compareTo(o2.toString());
     }
 }
diff --git a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java b/core/api/src/main/java/org/onosproject/ui/table/cell/DefaultCellFormatter.java
similarity index 78%
rename from core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java
rename to core/api/src/main/java/org/onosproject/ui/table/cell/DefaultCellFormatter.java
index 4078673..c030236 100644
--- a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java
+++ b/core/api/src/main/java/org/onosproject/ui/table/cell/DefaultCellFormatter.java
@@ -15,14 +15,14 @@
  *
  */
 
-package org.onosproject.ui.table;
+package org.onosproject.ui.table.cell;
 
 /**
  * A default cell formatter. Uses the object's toString() method.
  */
-public class DefaultCellFormatter implements CellFormatter {
+public class DefaultCellFormatter extends AbstractCellFormatter {
     @Override
-    public String format(Object value) {
-        return value == null ? "" : value.toString();
+    public String nonNullFormat(Object value) {
+        return value.toString();
     }
 }
diff --git a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java b/core/api/src/main/java/org/onosproject/ui/table/cell/HexFormatter.java
similarity index 71%
copy from core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java
copy to core/api/src/main/java/org/onosproject/ui/table/cell/HexFormatter.java
index 4078673..d4aaade 100644
--- a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java
+++ b/core/api/src/main/java/org/onosproject/ui/table/cell/HexFormatter.java
@@ -15,14 +15,14 @@
  *
  */
 
-package org.onosproject.ui.table;
+package org.onosproject.ui.table.cell;
 
 /**
- * A default cell formatter. Uses the object's toString() method.
+ * Formats integer values as hex strings.
  */
-public class DefaultCellFormatter implements CellFormatter {
+public class HexFormatter extends AbstractCellFormatter {
     @Override
-    public String format(Object value) {
-        return value == null ? "" : value.toString();
+    protected String nonNullFormat(Object value) {
+        return "0x" + Integer.toHexString((Integer) value);
     }
 }
diff --git a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java b/core/api/src/main/java/org/onosproject/ui/table/cell/IntComparator.java
similarity index 65%
copy from core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java
copy to core/api/src/main/java/org/onosproject/ui/table/cell/IntComparator.java
index 4078673..c399d53 100644
--- a/core/api/src/main/java/org/onosproject/ui/table/DefaultCellFormatter.java
+++ b/core/api/src/main/java/org/onosproject/ui/table/cell/IntComparator.java
@@ -15,14 +15,16 @@
  *
  */
 
-package org.onosproject.ui.table;
+package org.onosproject.ui.table.cell;
 
 /**
- * A default cell formatter. Uses the object's toString() method.
+ * An integer-based cell comparator.
+ * Note that null values are acceptable and are considered "smaller" than
+ * any non-null value.
  */
-public class DefaultCellFormatter implements CellFormatter {
+public class IntComparator extends AbstractCellComparator {
     @Override
-    public String format(Object value) {
-        return value == null ? "" : value.toString();
+    protected int nonNullCompare(Object o1, Object o2) {
+        return ((int) o1) - ((int) o2);
     }
 }