Java Arrays: Declaration, Initialization & Key Concepts Explained

Array Introduction

In Java, an array is an object that stores a fixed-size sequence of elements of the same data type. Arrays are used when you want to store multiple values of the same type in a single variable.

Key Features of Arrays in Java

Arrays hold similar types of data (e.g., only integers or only strings).

The array has a fixed size (cannot grow/shrink once declared).

Array elements are stored in contiguous memory.

Arrays are zero-indexed (i.e., the first element is at index 0).

You can access any element randomly using its index.

Java arrays are objects; they inherit from the Object class and implement Serializable and Cloneable.

How to Declare and Initialize Arrays in Java

1. Declaration Only

// Method 1
int integerArray[ ];

// Method 2
int[ ] integerArray;

Both declarations are valid and widely used in Java.

2. Initialization After Declaration

integerArray = new int[10]; // Array of size 10 (all values default to 0)

3. Declaration + Initialization

int[ ] integerArray = new int[10]; // Array with default values

int[ ] numbers = {1, 4, 6, 8, 10};  // Array initialized with specific values

Example: Java Array Declaration and Initialization

public class ArrayExample {
    public static void main(String[ ] args) {
        int[ ] numbers = {1, 4, 6, 8, 10};  // Declaration + initialization

        // Accessing elements
        System.out.println("First Element: " + numbers[0]);
        System.out.println("Third Element: " + numbers[2]);

        // Looping through the array
        for (int i = 0; i < numbers.length; i++) {
            System.out.println("Element at index " + i + ": " + numbers[i]);
        }
    }
}

Output:

First Element: 1  
Third Element: 6  
Element at index 0: 1  
Element at index 1: 4  
Element at index 2: 6  
Element at index 3: 8  
Element at index 4: 10