JAVA

Array Utility Methods

Arrays are useful for storing multiple values, but simply storing data is often not enough. In real applications, we frequently need to sort data, search for values, compare arrays, or fill an array with a default value.

Instead of writing this functionality from scratch every time, Java provides the Arrays utility class in the java.util package. This class contains several built-in methods that make working with arrays easier and more efficient.

In this chapter, you will learn some of the most commonly used array methods provided by Java.

The Arrays Class

Before using array utility methods, the Arrays class must be imported.

Syntax

import java.util.Arrays;

This gives access to methods such as:

• sort()
• toString()
• equals()
• fill()
• binarySearch()

Arrays.toString()

By default, printing an array directly does not display its elements.

Example

int[] numbers = {10, 20, 30};

System.out.println(numbers);

Output

[I@6d06d69c

This output represents the array's memory reference, not its contents.

To display the actual values, use Arrays.toString().

Example

import java.util.Arrays;

int[] numbers = {10, 20, 30};

System.out.println(Arrays.toString(numbers));

Output

[10, 20, 30]

Arrays.sort()

The sort() method arranges array elements in ascending order.

Example

import java.util.Arrays;

int[] numbers = {40, 10, 30, 20};

Arrays.sort(numbers);

System.out.println(Arrays.toString(numbers));

Output

[10, 20, 30, 40]

Explanation

The array is sorted from smallest to largest.

Arrays.equals()

The equals() method compares two arrays.

Example

import java.util.Arrays;

int[] arr1 = {10, 20, 30};
int[] arr2 = {10, 20, 30};

System.out.println(Arrays.equals(arr1, arr2));

Output

true

The result is true because both arrays contain the same values in the same order.

Arrays.fill()

The fill() method assigns the same value to every element in an array.

Example

import java.util.Arrays;

int[] numbers = new int[5];

Arrays.fill(numbers, 100);

System.out.println(Arrays.toString(numbers));

Output

[100, 100, 100, 100, 100]

Explanation

Every element in the array is replaced with 100.

Arrays.binarySearch()

The binarySearch() method searches for an element and returns its index.

Important: The array must be sorted before using this method.

Example

import java.util.Arrays;

int[] numbers = {10, 20, 30, 40, 50};

int index = Arrays.binarySearch(numbers, 30);

System.out.println(index);

Output

2

The value 30 is found at index 2.

Copying Arrays

Arrays can be copied using Arrays.copyOf().

Example

import java.util.Arrays;

int[] original = {10, 20, 30};

int[] copy = Arrays.copyOf(original, original.length);

System.out.println(Arrays.toString(copy));

Output

[10, 20, 30]

A new array is created containing the same values.

Sorting Strings

The sort() method also works with String arrays.

Example

import java.util.Arrays;

String[] names = {"Rahul", "Ankit", "Priya", "Kiran"};

Arrays.sort(names);

System.out.println(Arrays.toString(names));

Output

[Ankit, Kiran, Priya, Rahul]

Strings are sorted alphabetically.

Common Array Utility Methods

The Arrays class provides many utility methods for working with arrays. The following table contains the most commonly used methods that every Java developer should know.

Methods You Should Focus On Initially

When learning arrays, concentrate on these methods:

• Arrays.toString()
• Arrays.sort()
• Arrays.equals()
• Arrays.fill()
• Arrays.binarySearch()
• Arrays.copyOf()

The remaining methods become more useful when learning Streams, Functional Programming, Multithreading, and Advanced Java.

Complete Program

Example

import java.util.Arrays;

public class Main {

    public static void main(String[] args) {

        int[] prices = {500, 200, 1000, 300, 700};

        Arrays.sort(prices);

        System.out.println("Sorted Prices:");
        System.out.println(Arrays.toString(prices));
    }
}

Output

Sorted Prices:
[200, 300, 500, 700, 1000]

Explanation

• An array stores product prices.
• Arrays.sort() arranges them in ascending order.
• Arrays.toString() displays the array contents.

Common Mistakes

Printing Arrays Directly

Wrong

System.out.println(numbers);

Output

[I@6d06d69c

Correct

System.out.println(Arrays.toString(numbers));

Using binarySearch() on an Unsorted Array

Wrong

int[] numbers = {40, 10, 30, 20};

Arrays.binarySearch(numbers, 30);

The result may be incorrect.

Correct

Arrays.sort(numbers);
Arrays.binarySearch(numbers, 30);

Always sort the array before using binarySearch().

Key Takeaways

• The Arrays class provides useful methods for working with arrays.
• Arrays.toString() displays array contents.
• Arrays.sort() sorts array elements.
• Arrays.equals() compares arrays.
• Arrays.fill() assigns a value to every element.
• Arrays.binarySearch() searches for an element in a sorted array.
• Arrays.copyOf() creates a copy of an array.
• These methods help reduce code and simplify common array operations.