Issue 439: Utils.sortTopN does not handle single-element arrays.

h2/src/docsrc/html/changelog.html

@@ -66,6 +66,7 @@ Change Log
 </li><li>MySQL compatibility: support for ALTER TABLE tableName MODIFY [COLUMN] columnName columnDef. Patch from Ville Koskela.
 </li><li>Issue 404: SHOW COLUMNS FROM tableName does not work with ALLOW_LITERALS=NUMBERS.
 </li><li>Throw an explicit error to make it clear we don't support the TRIGGER combination of SELECT and FOR EACH ROW.
+</li><li>Issue 439: Utils.sortTopN does not handle single-element arrays.
 </li></ul>
 
 <h2>Version 1.3.170 (2012-11-30)</h2>

h2/src/main/org/h2/util/Utils.java

@@ -469,6 +469,9 @@ public class Utils {
         if (low > end || high < start || (low > start && high < end)) {
             return;
         }
+        if (low == high) {
+            return;
+        }
         int i = low, j = high;
         // use a random pivot to protect against
         // the worst case order

h2/src/test/org/h2/test/unit/TestUtils.java

@@ -16,6 +16,7 @@ import java.util.Date;
 import java.util.Random;
 import org.h2.test.TestBase;
 import org.h2.util.Utils;
+import org.junit.Test;
 
 /**
  * Tests reflection utilities.
@@ -36,13 +37,15 @@ public class TestUtils extends TestBase {
         TestBase.createCaller().init().test();
     }
 
+    @Test
     public void test() throws Exception {
+        testSortTopN();
+        testSortTopNRandom();
         testWriteReadLong();
         testGetNonPrimitiveClass();
         testGetNonPrimitiveClass();
         testGetNonPrimitiveClass();
         testReflectionUtils();
-        testSortTopN();
     }
 
     private void testWriteReadLong() {
@@ -63,6 +66,25 @@ public class TestUtils extends TestBase {
     }
     
     private void testSortTopN() {
+        Comparator<Integer> comp = new Comparator<Integer>() {
+            @Override
+            public int compare(Integer o1, Integer o2) {
+                return o1.compareTo(o2);
+            }
+        };
+        Integer[] arr = new Integer[] {};
+        Utils.sortTopN(arr, 0, 5, comp);
+
+        arr = new Integer[] { 1 };
+        Utils.sortTopN(arr, 0, 5, comp);
+
+        arr = new Integer[] { 3, 5, 1, 4, 2 };
+        Utils.sortTopN(arr, 0, 2, comp);
+        assertEquals(arr[0].intValue(), 1);
+        assertEquals(arr[1].intValue(), 2);
+    }
+
+    private void testSortTopNRandom() {
         Random rnd = new Random();
         Comparator<Integer> comp = new Comparator<Integer>() {
             @Override