src/share/classes/java/util/Collections.java

@@ -150,10 +150,13 @@
      *         detects that the natural ordering of the list elements is
      *         found to violate the {@link Comparable} contract
      */
     public static <T extends Comparable<? super T>> void sort(List<T> list) {
         Object[] a = list.toArray();
+        if(a.length <= 1) {
+            return;
+        }
         Arrays.sort(a);
         ListIterator<T> i = list.listIterator();
         for (int j=0; j<a.length; j++) {
             i.next();
             i.set((T)a[j]);

@@ -212,15 +215,18 @@
      * @throws IllegalArgumentException (optional) if the comparator is
      *         found to violate the {@link Comparator} contract
      */
     public static <T> void sort(List<T> list, Comparator<? super T> c) {
         Object[] a = list.toArray();
+        if(a.length <= 1) {
+            return;
+        }
         Arrays.sort(a, (Comparator)c);
-        ListIterator i = list.listIterator();
+        ListIterator<T> i = list.listIterator();
         for (int j=0; j<a.length; j++) {
             i.next();
-            i.set(a[j]);
+            i.set((T) a[j]);
         }
     }
 
 
     /**