---
title: "Arrays in Java"
description: One-dimensional and multi-dimensional arrays, declaration, initialization, and common operations.
---
## Types of Arrays

- **One-dimensional arrays** — A linear sequence of elements of the same type.
- **Multi-dimensional arrays** — Arrays of arrays (e.g., 2D matrices).

## Declaration and Initialization

```java
// Declaration and initialization
int[] numbers = {1, 2, 3, 4, 5};

// Declaration with size
int[] arr = new int[10];

// 2D array
int[][] matrix = {
    {1, 2},
    {3, 4}
};
```

## Common Operations

- **Accessing elements** — `array[index]` (zero-based indexing).
- **Length** — `array.length` returns the number of elements.
- **Looping** — Standard `for` loop or enhanced `for` loop.

```java
// Standard for loop
for (int i = 0; i < arr.length; i++) { ... }

// Enhanced for loop
for (int num : numbers) { ... }
```

## Example

```java
// ArrayDemo.java
// Demonstrates one-dimensional and two-dimensional arrays in Java.

public class ArrayDemo {
	public static void main(String[] args) {
		// One-dimensional array
		int[] numbers = {1, 2, 3, 4, 5};
		// Enhanced for loop to print elements
		for (int num : numbers) {
			System.out.println(num);
		}

		// Two-dimensional array
		int[][] matrix = {
			{1, 2},
			{3, 4}
		};
		// Print element at [1][0]
		System.out.println("Matrix[1][0]: " + matrix[1][0]);
	}
}
```

> Full source: [`examples/07-arrays/ArrayDemo.java`](https://github.com/University-Of-Sri-Jayewardenepura/Java/blob/main/examples/07-arrays/ArrayDemo.java)