Append the given Object to the given array : Arrays Utilities « Collections « Java Tutorial

import java.lang.reflect.Array;
import java.util.Arrays;

 * Copyright 2002-2007 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.
 * You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

//Revised from springframework

 * Miscellaneous object utility methods. Mainly for internal use within the
 * framework; consider Jakarta's Commons Lang for a more comprehensive suite
 * of object utilities.
 * @author Juergen Hoeller
 * @author Keith Donald
 * @author Rod Johnson
 * @author Rob Harrop
 * @author Alex Ruiz
 * @since 19.03.2004
 * @see org.apache.commons.lang.ObjectUtils
abstract class ObjectUtils {

  private static final int INITIAL_HASH = 7;
  private static final int MULTIPLIER = 31;

  private static final String EMPTY_STRING = "";
  private static final String NULL_STRING = "null";
  private static final String ARRAY_START = "{";
  private static final String ARRAY_END = "}";
  private static final String EMPTY_ARRAY = ARRAY_START + ARRAY_END;
  private static final String ARRAY_ELEMENT_SEPARATOR = ", ";

   * Return whether the given array is empty: that is, <code>null</code>
   * or of zero length.
   * @param array the array to check
   * @return whether the given array is empty
  public static boolean isEmpty(Object[] array) {
    return (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</code>)
   * @param obj the Object to append
   * @return the new array (of the same component type; never <code>null</code>)
  public static Object[] addObjectToArray(Object[] array, Object obj) {
    Class compType = Object.class;
    if (array != null) {
      compType = array.getClass().getComponentType();
    else if (obj != null) {
      compType = obj.getClass();
    int newArrLength = (array != null ? array.length + 1 : 1);
    Object[] newArr = (Object[]) Array.newInstance(compType, newArrLength);
    if (array != null) {
      System.arraycopy(array, 0, newArr, 0, array.length);
    newArr[newArr.length - 1] = obj;
    return newArr;

   * Convert the given array (which may be a primitive array) to an
   * object array (if necessary of primitive wrapper objects).
   * A <code>null</code> source value will be converted to an
   * empty Object array.
   * @param source the (potentially primitive) array
   * @return the corresponding object array (never <code>null</code>)
   * @throws IllegalArgumentException if the parameter is not an array
  public static Object[] toObjectArray(Object source) {
    if (source instanceof Object[]) {
      return (Object[]) source;
    if (source == null) {
      return new Object[0];
    if (!source.getClass().isArray()) {
      throw new IllegalArgumentException("Source is not an array: " + source);
    int length = Array.getLength(source);
    if (length == 0) {
      return new Object[0];
    Class wrapperType = Array.get(source, 0).getClass();
    Object[] newArray = (Object[]) Array.newInstance(wrapperType, length);
    for (int i = 0; i < length; i++) {
      newArray[i] = Array.get(source, i);
    return newArray;


9.9.Arrays Utilities
9.9.1.How to sort an array
9.9.2.Sorting an Array in Descending (Reverse) Order
9.9.3.Shuffle elements of an array
9.9.4.Minimum and maximum number in array
9.9.5.Convert an Array to a List
9.9.6.Extend the size of an array
9.9.7.How to copy an array
9.9.8.Performing Binary Search on Java Array
9.9.9.Java Sort byte Array
9.9.10.Java Sort char Array
9.9.11.Java Sort double Array
9.9.12.Java Sort float Array
9.9.13.Sort an array: case-sensitive
9.9.14.Sort an array: case-insensitive provides ways to dump the content of an array.
9.9.16.Dump multi-dimensional arrays
9.9.17.Use java.util.Arrays.deepToString() to dump the multi-dimensional arrays
9.9.18.Shifting Elements in an Array: Shift all elements right by one
9.9.19.Shifting Elements in an Array: Shift all elements left by one
9.9.20.Compare two byte type arrays
9.9.21.Compare two char type arrays
9.9.22.Compare two short type arrays
9.9.23.Compare two int type arrays
9.9.24.Compare two long type arrays
9.9.25.Compare two float type arrays
9.9.26.Compare two double type arrays
9.9.27.Filling Elements in an Array
9.9.28.filling object arrays:
9.9.29.fill to a contiguous range of elements in an array
9.9.30.If the given objects are equal
9.9.31.Append the given Object to the given array
9.9.32.Array To String
9.9.33.Convert the given array (which may be a primitive array) to an object array
9.9.34.Gets the subarray from array that starts at offset.
9.9.35.Gets the subarray of length length from array that starts at offset.
9.9.36.Growable String array with type specific access methods.
9.9.37.Wrapper for arrays of ordered strings. This verifies the arrays and supports efficient lookups.
9.9.38.Reverses the order of the given object array.