Add subArray method to get a portion of an array

from Ash


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@137713 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/lang/ArrayUtils.java

@@ -78,8 +78,9 @@
  * @author Tim O'Brien
  * @author Pete Gieser
  * @author Gary Gregory
+ * @author Ash
  * @since 2.0
- * @version $Id: ArrayUtils.java,v 1.25 2003/08/22 17:25:33 ggregory Exp $
+ * @version $Id: ArrayUtils.java,v 1.26 2003/11/29 12:56:15 scolebourne Exp $
  */
 public class ArrayUtils {
 
@@ -435,6 +436,44 @@ public static boolean[] clone(final boolean[] array) {
         return (boolean[]) array.clone();
     }
 
+    // Subarrays
+    //-----------------------------------------------------------------------
+    /**
+     * <p>Produces a new array containing the elements between
+     * the start and end indices.</p>
+     * 
+     * <p>The start index is inclusive, the end index exclusive.
+     * Null array input produces null output.
+     * The result is always an <code>Object[]</code> instance</p>
+     *
+     * @param array  the array
+     * @param startIndex  the starting index. Undervalue (&lt;0)
+     *      is promoted to 0, overvalue (&gt;array.length) results
+     *      in an empty array.
+     * @param endIndex  elements upto endIndex-1 are present in the
+     *      returned subarray. Undervalue (&lt; startIndex) produces
+     *      empty array, overvalue (&gt;array.length) is demoted to
+     *      array length.
+     */
+    public static Object[] subArray(Object[] array, int startIndexInclusive, int endIndexExclusive) {
+        if (array == null) {
+            return null;
+        }
+        if (startIndexInclusive < 0) {
+            startIndexInclusive = 0;
+        }
+        if (endIndexExclusive > array.length) {
+            endIndexExclusive = array.length;
+        }
+        int newSize = endIndexExclusive - startIndexInclusive;
+        if (newSize <= 0) {
+            return EMPTY_OBJECT_ARRAY;
+        }
+        Object[] subArray = new Object[newSize];
+        System.arraycopy(array, startIndexInclusive, subArray, 0, newSize);
+        return subArray;
+    }
+
     // Is same length
     //-----------------------------------------------------------------------
     /**

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

@@ -71,7 +71,7 @@
  * @author Nikolay Metchev
  * @author Matthew Hawthorne
  * @author Tim O'Brien
- * @version $Id: ArrayUtilsTest.java,v 1.14 2003/10/11 19:58:40 tobrien Exp $
+ * @version $Id: ArrayUtilsTest.java,v 1.15 2003/11/29 12:56:16 scolebourne Exp $
  */
 public class ArrayUtilsTest extends TestCase {
 
@@ -271,6 +271,49 @@ public void testCloneFloat() {
         assertTrue(original != cloned);
     }
 
+    //-----------------------------------------------------------------------
+
+    public void testSubArray() {
+        Object[] inarray = { "a", "b", "c", "d", "e", "f"};
+
+        assertEquals("0 start, mid end", "abcd",
+            StringUtils.join(ArrayUtils.subArray(inarray, 0, 4)));
+        assertEquals("0 start, length end", "abcdef",
+            StringUtils.join(ArrayUtils.subArray(inarray, 0, inarray.length)));
+        assertEquals("mid start, mid end", "bcd",
+            StringUtils.join(ArrayUtils.subArray(inarray, 1, 4)));
+        assertEquals("mid start, length end", "bcdef",
+            StringUtils.join(ArrayUtils.subArray(inarray, 1, inarray.length)));
+
+        assertNull("null input", ArrayUtils.subArray(null, 0, 3));
+        assertEquals("empty array", "",
+            StringUtils.join(ArrayUtils.subArray(ArrayUtils.EMPTY_OBJECT_ARRAY, 1, 2)));
+        assertEquals("start > end", "",
+            StringUtils.join(ArrayUtils.subArray(inarray, 4, 2)));
+        assertEquals("start == end", "",
+            StringUtils.join(ArrayUtils.subArray(inarray, 3, 3)));
+        assertEquals("start undershoot, normal end", "abcd",
+            StringUtils.join(ArrayUtils.subArray(inarray, -2, 4)));
+        assertEquals("start overshoot, any end", "",
+            StringUtils.join(ArrayUtils.subArray(inarray, 33, 4)));
+        assertEquals("normal start, end overshoot", "cdef",
+            StringUtils.join(ArrayUtils.subArray(inarray, 2, 33)));
+        assertEquals("start undershoot, end overshoot", "abcdef",
+            StringUtils.join(ArrayUtils.subArray(inarray, -2, 12)));
+            
+        // object-level tests
+        assertSame("empty array, object test", ArrayUtils.EMPTY_OBJECT_ARRAY,
+            ArrayUtils.subArray(ArrayUtils.EMPTY_OBJECT_ARRAY, 1, 2));
+        assertSame("start > end, object test", ArrayUtils.EMPTY_OBJECT_ARRAY,
+            ArrayUtils.subArray(inarray, 4, 1));
+        assertSame("start > end, object test", ArrayUtils.EMPTY_OBJECT_ARRAY,
+            ArrayUtils.subArray(inarray, 33, 1));
+        assertSame("start == end, object test", ArrayUtils.EMPTY_OBJECT_ARRAY,
+            ArrayUtils.subArray(inarray, 3, 3));
+        assertSame("start overshoot, any end, object test", ArrayUtils.EMPTY_OBJECT_ARRAY,
+            ArrayUtils.subArray(inarray, 8733, 4));
+    }
+
     //-----------------------------------------------------------------------
     public void testSameLength() {
         Object[] nullArray = null;