[LANG-920] Add ArrayUtils#nullToEmpty(Class<?>[])

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1531399 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/lang3/ArrayUtils.java

@@ -473,6 +473,26 @@ public class ArrayUtils {
         return array;
     }
 
+    /**
+     * <p>Defensive programming technique to change a {@code null}
+     * reference to an empty one.</p>
+     *
+     * <p>This method returns an empty array for a {@code null} input array.</p>
+     *
+     * <p>As a memory optimizing technique an empty array passed in will be overridden with
+     * the empty {@code public static} references in this class.</p>
+     *
+     * @param array  the array to check for {@code null} or empty
+     * @return the same array, {@code public static} empty array if {@code null} or empty input
+     * @since 3.2
+     */
+    public static Class<?>[] nullToEmpty(final Class<?>[] array) {
+        if (array == null || array.length == 0) {
+            return EMPTY_CLASS_ARRAY;
+        }
+        return array;
+    }
+
     /**
      * <p>Defensive programming technique to change a {@code null}
      * reference to an empty one.</p>

src/test/java/org/apache/commons/lang3/ArrayUtilsTest.java

@@ -488,6 +488,20 @@ public class ArrayUtilsTest  {
         assertTrue(empty != result);
     }
 
+    @Test
+    public void testNullToEmptyClass() {
+        // Test null handling
+        assertArrayEquals(ArrayUtils.EMPTY_CLASS_ARRAY, ArrayUtils.nullToEmpty((Class<?>[]) null));
+        // Test valid array handling
+        final Class<?>[] original = { Object.class, String.class };
+        assertArrayEquals(original, ArrayUtils.nullToEmpty(original));
+        // Test empty array handling
+        final Class<?>[] empty = {};
+        final Class<?>[] result = ArrayUtils.nullToEmpty(empty);
+        assertArrayEquals(ArrayUtils.EMPTY_CLASS_ARRAY, result);
+        assertTrue(empty != result);
+    }
+
     @Test
     public void testNullToEmptyString() {
         // Test null handling