diff --git a/src/main/java/org/rometools/feed/module/sle/SleUtility.java b/src/main/java/org/rometools/feed/module/sle/SleUtility.java
index b92ac6f..a08c106 100644
--- a/src/main/java/org/rometools/feed/module/sle/SleUtility.java
+++ b/src/main/java/org/rometools/feed/module/sle/SleUtility.java
@@ -56,11 +56,11 @@ public final class SleUtility {
      * @param groups Group fields (from the SimpleListExtension module)
      * @return Grouped list of entries.
      */
-    public static List<Extendable> group(final List<Extendable> values, final Group[] groups) {
-        final SortableList list = values instanceof SortableList ? (SortableList) values : new SortableList(values);
-        final GroupStrategy gs = new GroupStrategy();
+    public static <T extends Extendable> List<T> group(final List<T> values, final Group[] groups) {
+        final SortableList<T> list = getSortableList(values);
+        final GroupStrategy strategy = new GroupStrategy();
         for (int i = groups.length - 1; i >= 0; i--) {
-            list.sortOnProperty(groups[i], true, gs);
+            list.sortOnProperty(groups[i], true, strategy);
         }
         return list;
     }
@@ -73,13 +73,8 @@ public final class SleUtility {
      * @param ascending Sort ascending/descending.
      * @return Sorted list of values
      */
-    public static List<Extendable> sort(final List<Extendable> values, final Sort sort, final boolean ascending) {
-        final SortableList list;
-        if (values instanceof SortableList) {
-            list = (SortableList) values;
-        } else {
-            list = new SortableList(values);
-        }
+    public static <T extends Extendable> List<T> sort(final List<T> values, final Sort sort, final boolean ascending) {
+        final SortableList<T> list = getSortableList(values);
         list.sortOnProperty(sort, ascending, new SortStrategy());
         return list;
     }
@@ -93,8 +88,8 @@ public final class SleUtility {
      * @param ascending Sort ascending/descending
      * @return Grouped and sorted list of entries.
      */
-    public static List<Extendable> sortAndGroup(final List<Extendable> values, final Group[] groups, final Sort sort, final boolean ascending) {
-        List<Extendable> list = sort(values, sort, ascending);
+    public static <T extends Extendable> List<T> sortAndGroup(final List<T> values, final Group[] groups, final Sort sort, final boolean ascending) {
+        List<T> list = sort(values, sort, ascending);
         list = group(list, groups);
         return list;
     }
@@ -115,4 +110,14 @@ public final class SleUtility {
         feed.copyFrom(copy);
     }
 
+    private static <T extends Extendable> SortableList<T> getSortableList(final List<T> list) {
+        SortableList<T> sortableList;
+        if (list instanceof SortableList) {
+            sortableList = (SortableList<T>) list;
+        } else {
+            sortableList = new SortableList<T>(list);
+        }
+        return sortableList;
+    }
+
 }
diff --git a/src/main/java/org/rometools/feed/module/sle/SortableList.java b/src/main/java/org/rometools/feed/module/sle/SortableList.java
index d1c8318..7bf557b 100644
--- a/src/main/java/org/rometools/feed/module/sle/SortableList.java
+++ b/src/main/java/org/rometools/feed/module/sle/SortableList.java
@@ -5,11 +5,11 @@ import java.util.Collection;
 
 import com.sun.syndication.feed.module.Extendable;
 
-class SortableList extends ArrayList<Extendable> {
+class SortableList<T extends Extendable> extends ArrayList<T> {
 
     private static final long serialVersionUID = 1L;
 
-    public SortableList(final Collection<Extendable> c) {
+    public SortableList(final Collection<T> c) {
         super(c);
     }
 
@@ -20,10 +20,10 @@ class SortableList extends ArrayList<Extendable> {
         for (int i = 0; i < size() - 1; i++) {
             for (int j = i + 1; j < size(); j++) {
 
-                final Extendable o1 = get(i);
+                final T o1 = get(i);
                 final Comparable oc1 = strat.getValue(o1, value);
 
-                final Extendable o2 = get(j);
+                final T o2 = get(j);
                 final Comparable oc2 = strat.getValue(o2, value);
 
                 System.out.println(oc1 + " < " + oc2);
diff --git a/src/test/java/org/rometools/feed/module/sle/GroupAndSortTest.java b/src/test/java/org/rometools/feed/module/sle/GroupAndSortTest.java
index e215175..75c5f50 100644
--- a/src/test/java/org/rometools/feed/module/sle/GroupAndSortTest.java
+++ b/src/test/java/org/rometools/feed/module/sle/GroupAndSortTest.java
@@ -37,41 +37,41 @@ public class GroupAndSortTest extends AbstractTestCase {
         final File testdata = new File(super.getTestFile("data/bookexample.xml"));
         final SyndFeed feed = new SyndFeedInput().build(testdata);
 
-        final List<SyndEntry> feedEntries = feed.getEntries();
-        final List<Extendable> entries = new ArrayList<Extendable>(feedEntries);
+        List<SyndEntry> entries = feed.getEntries();
 
-        final SimpleListExtension sle = (SimpleListExtension) feed.getModule(SimpleListExtension.URI);
-        final Sort[] sortFields = sle.getSortFields();
+        final SimpleListExtension extention = (SimpleListExtension) feed.getModule(SimpleListExtension.URI);
+        final Sort[] sortFields = extention.getSortFields();
 
         final Sort sortByDate = sortFields[1];
         final Sort sortByTitle = sortFields[2];
 
         // sort by date ascending
-        List<Extendable> sortedEntries = SleUtility.sort(entries, sortByDate, true);
-        SyndEntry entry = (SyndEntry) sortedEntries.get(0);
+        List<SyndEntry> sortedEntries = SleUtility.sort(entries, sortByDate, true);
+        SyndEntry entry = sortedEntries.get(0);
         assertEquals("Great Journeys of the Past", entry.getTitle());
 
         // sort by date descending
         sortedEntries = SleUtility.sort(entries, sortByDate, false);
-        entry = (SyndEntry) sortedEntries.get(0);
+        entry = sortedEntries.get(0);
         assertEquals("Horror Stories, vol 16", entry.getTitle());
 
         // sort by date ascending
         sortedEntries = SleUtility.sort(entries, sortByDate, true);
 
         // update first entry and reinitialize
-        entry = (SyndEntry) sortedEntries.get(0);
+        entry = sortedEntries.get(0);
         entry.setTitle("ZZZZZ");
         SleUtility.initializeForSorting(feed);
+        entries = feed.getEntries();
 
         // sort by title desc
         sortedEntries = SleUtility.sort(entries, sortByTitle, false);
-        entry = (SyndEntry) sortedEntries.get(0);
+        entry = sortedEntries.get(0);
         assertEquals("ZZZZZ", entry.getTitle());
 
         // sort by title asc
         sortedEntries = SleUtility.sort(entries, sortByTitle, true);
-        entry = (SyndEntry) sortedEntries.get(0);
+        entry = sortedEntries.get(0);
         assertEquals("Horror Stories, vol 16", entry.getTitle());
 
     }