ArrayUtils

About

ArrayUtils is a utility class provided by Apache Commons Lang to simplify working with Java arrays. Java arrays are low-level and have limited built-in methods, making operations like searching, copying, checking for emptiness, or merging somewhat cumbersome.

ArrayUtils provides null-safe, convenient, and readable methods to handle arrays of all primitive types and objects. It also helps avoid manual loops, System.arraycopy, and verbose boilerplate code.

Characteristics

• All methods are static.

• Handles both primitive and object arrays.

• Offers null safety — no need to check for null before calling utility methods.

• Reduces common array operations to one-liners.

Maven Dependency & Import

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version> <!-- or latest -->
</dependency>

import org.apache.commons.lang3.ArrayUtils;

Common Categories of Methods

1. Null and Empty Checks

Method	Description
isEmpty(array)	Returns true if array is null or length is 0
isNotEmpty(array)	Returns true if array is not null and has elements

Example:

if (ArrayUtils.isEmpty(myArray)) {
    // safely handle empty case
}

2. Array Creation and Conversion

Method	Description
toObject(int[])	Converts a primitive array to wrapper array
toPrimitive(Integer[])	Converts wrapper array to primitive array
nullToEmpty(array)	Converts null array to empty array

Example:

int[] ints = {1, 2, 3};
Integer[] boxed = ArrayUtils.toObject(ints);

3. Element Checks

Method	Description
contains(array, value)	Checks if array contains a specific element
indexOf(array, value)	Returns the index of the element, or -1
lastIndexOf(array, value)	Returns the last index of the element

Example:

if (ArrayUtils.contains(new int[]{1, 2, 3}, 2)) {
    // element found
}

4. Adding and Removing Elements

Method	Description
add(array, value)	Adds value at the end
add(array, index, value)	Inserts value at a specific index
remove(array, index)	Removes value at index
removeElement(array, value)	Removes first occurrence of value

Example:

int[] result = ArrayUtils.add(new int[]{1, 2}, 3); // [1, 2, 3]

5. Concatenation and Cloning

Method	Description
addAll(array1, array2)	Concatenates arrays
clone(array)	Returns a clone of the array
subarray(array, startIndex, endIndex)	Gets a range of elements

Example:

int[] combined = ArrayUtils.addAll(new int[]{1, 2}, new int[]{3, 4});

6. Array Reversal and Shuffling

Method	Description
reverse(array)	Reverses the array in place
shuffle(array)	Randomizes the order (not in standard ArrayUtils, but can use custom logic)

Example:

int[] nums = {1, 2, 3};
ArrayUtils.reverse(nums); // nums becomes {3, 2, 1}

7. Equality and Comparison

Method	Description
isSameLength(array1, array2)	Checks if two arrays are of the same length
isEquals(array1, array2)	Checks if all elements are equal

8. Array Type Checking

Method	Description
isArray(Object obj)	Checks whether a given object is an array

Why Use ArrayUtils Instead of Raw Java?

Concern	Raw Java Approach	ArrayUtils Advantage
Null-safety	Manual checks	Built-in null checks
Adding/removing	Manual resizing or arraycopy	Simple one-liners
Searching	Manual loops	Ready-made methods
Conversion	Tedious type boxing/unboxing	Simplified conversions