Java Array Methods That Actually Make Sense

Source: Dev.to

Arrays were honestly confusing at first. Not the concept — storing multiple values, fine. But all the utility methods scattered across different classes? That took a while to click.

Two Classes You Need to Know

Most array utility methods live in java.util.Arrays — you need to import it.

For resizing and dynamic stuff, ArrayList is your friend (but that’s a separate topic).

import java.util.Arrays;

Array Utility Methods

Arrays.sort()

Sorts your array in ascending order. Works for numbers and strings.

int[] nums = {5, 2, 8, 1, 9};
Arrays.sort(nums);
// nums is now {1, 2, 5, 8, 9}

Arrays.toString()

Useful for debugging. Prints array contents instead of a memory address.

int[] nums = {1, 2, 3};
System.out.println(nums);                     // [I@6d06d69c  ← useless
System.out.println(Arrays.toString(nums));   // [1, 2, 3]   ← useful

Arrays.fill()

Fills all elements with a single value. Handy for initialization.

int[] grid = new int[5];
Arrays.fill(grid, 0);
// {0, 0, 0, 0, 0}

Arrays.copyOf()

Copies an array into a new one. You can also resize it while copying.

int[] original = {1, 2, 3, 4, 5};
int[] copy = Arrays.copyOf(original, 3);
// copy = {1, 2, 3}

Arrays.copyOfRange()

Copies a specific slice of the array.

int[] nums = {10, 20, 30, 40, 50};
int[] slice = Arrays.copyOfRange(nums, 1, 4);
// slice = {20, 30, 40}

Arrays.equals()

Checks if two arrays have the same values in the same order.

int[] a = {1, 2, 3};
int[] b = {1, 2, 3};

System.out.println(a == b);                 // false (different objects)
System.out.println(Arrays.equals(a, b));    // true ✅

Same lesson as strings — never use == to compare arrays.

Arrays.binarySearch()

Searches for a value and returns its index. Sort the array first, otherwise results are unpredictable.

int[] nums = {1, 3, 5, 7, 9};
int index = Arrays.binarySearch(nums, 5);
// index = 2

array.length

Not a method, it’s a property. Use it everywhere.

int[] nums = {4, 8, 15, 16, 23};
System.out.println(nums.length); // 5

No parentheses — just .length, not .length().

Quick Reference

One Thing to Remember

Arrays in Java have a fixed size — once created, you can’t add or remove elements. If you need a resizable list, use ArrayList.

// Fixed size — can't grow
int[] arr = new int[5];

// Flexible — can add/remove
ArrayList list = new ArrayList<>();

That’s a whole other post though. 😄

Got questions or want me to cover ArrayList next? Drop a comment below!

Happy coding 🙌