new test case

explanations about algorithm

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

@@ -2650,6 +2650,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -2708,6 +2710,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -2766,6 +2770,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -2824,6 +2830,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -2882,6 +2890,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -2940,6 +2950,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -2997,6 +3009,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -3054,6 +3068,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             
@@ -3112,6 +3128,8 @@ public class ArrayUtils {
         if (offset < 0) {
             offset += n;
         }
+        // For algorithm explanations and proof of O(n) time complexity and O(1) space complexity
+        // see https://beradrian.wordpress.com/2015/04/07/shift-an-array-in-on-in-place/
         while (n > 1 && offset > 0) {
             int n_offset = n - offset;
             

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

@@ -2484,6 +2484,13 @@ public class ArrayUtilsTest  {
         assertEquals(4, array[1]);
         assertEquals(1, array[2]);
         assertEquals(2, array[3]);
+        array = new short[] {1, 2, 3, 4, 5};
+        ArrayUtils.shift(array, 2);
+        assertEquals(4, array[0]);
+        assertEquals(5, array[1]);
+        assertEquals(1, array[2]);
+        assertEquals(2, array[3]);
+        assertEquals(3, array[4]);
     }
 
     @Test