Arrays in Java

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

// 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.

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

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

Example

// 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