Add position variant of ObjectUtils.addObjectToArray

Add an overloaded version of `ObjectUtils.addObjectToArray` that allows
inserts at a specific position.

Closes gh-28415

spring-core/src/main/java/org/springframework/util/ObjectUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -250,6 +250,17 @@ public abstract class ObjectUtils {
 	 * @return the new array (of the same component type; never {@code null})
 	 */
 	public static <A, O extends A> A[] addObjectToArray(@Nullable A[] array, @Nullable O obj) {
+		return addObjectToArray(array, obj, (array != null) ? array.length : 0);
+	}
+
+	/**
+	 * Append the given object to the given array, returning a new array
+	 * consisting of the input array contents plus the given object.
+	 * @param array the array to append to (can be {@code null})
+	 * @param obj the object to append
+	 * @return the new array (of the same component type; never {@code null})
+	 */
+	public static <A, O extends A> A[] addObjectToArray(@Nullable A[] array, @Nullable O obj, int position) {
 		Class<?> compType = Object.class;
 		if (array != null) {
 			compType = array.getClass().getComponentType();
@@ -261,9 +272,10 @@ public abstract class ObjectUtils {
 		@SuppressWarnings("unchecked")
 		A[] newArr = (A[]) Array.newInstance(compType, newArrLength);
 		if (array != null) {
-			System.arraycopy(array, 0, newArr, 0, array.length);
+			System.arraycopy(array, 0, newArr, 0, position);
+			System.arraycopy(array, position, newArr, position + 1, array.length - position);
 		}
-		newArr[newArr.length - 1] = obj;
+		newArr[position] = obj;
 		return newArr;
 	}
 

spring-core/src/test/java/org/springframework/util/ObjectUtilsTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -182,6 +182,15 @@ class ObjectUtilsTests {
 		assertThat(newArray[2]).isEqualTo(newElement);
 	}
 
+	@Test
+	void addObjectToArraysAtPosition() {
+		String[] array = new String[] {"foo", "bar", "baz"};
+		assertThat(ObjectUtils.addObjectToArray(array, "bat", 3)).containsExactly("foo", "bar", "baz", "bat");
+		assertThat(ObjectUtils.addObjectToArray(array, "bat", 2)).containsExactly("foo", "bar", "bat", "baz");
+		assertThat(ObjectUtils.addObjectToArray(array, "bat", 1)).containsExactly("foo", "bat", "bar", "baz");
+		assertThat(ObjectUtils.addObjectToArray(array, "bat", 0)).containsExactly("bat", "foo", "bar", "baz");
+	}
+
 	@Test
 	void addObjectToArrayWhenEmpty() {
 		String[] array = new String[0];