📚 Java Arrays

Arrays in Java are used to store multiple values in a single variable, rather than declaring separate variables for each value. They allow you to store homogeneous (same type) data elements, making it easier to manage large amounts of data.

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🧭 What is an Array?

An array is a collection of similar data elements stored at contiguous memory locations. You can access array elements using indices.

java
int[] numbers = {10, 20, 30, 40, 50};
System.out.println(numbers[2]); // Output: 30

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🗂️ Types of Arrays in Java

1. Single-dimensional array – A simple list of values.

2. Multi-dimensional array – An array of arrays, like a matrix.

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1️⃣ Single-Dimensional Array

A single-dimensional array is like a list of items.

java
int[] numbers = new int[5]; // Declare an array of size 5
numbers[0] = 10;  // Assigning value to the first element
numbers[1] = 20;  // Assigning value to the second element
System.out.println(numbers[0]);  // Output: 10

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2️⃣ Multi-Dimensional Array

Multi-dimensional arrays are arrays of arrays, and they can represent things like tables or matrices.

Example of 2D Array (Matrix):

java
int[][] matrix = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
};
System.out.println(matrix[1][2]);  // Output: 6 (second row, third column)

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🧑‍💻 Array Operations

Accessing Array Elements

Arrays are accessed using indices. The index starts from 0.

java
int[] numbers = {1, 2, 3, 4, 5};
System.out.println(numbers[0]);  // Output: 1

Array Length

You can get the length of an array using the length property.

java
int[] numbers = {10, 20, 30};
System.out.println(numbers.length);  // Output: 3

Traversing an Array (Looping through the elements)

java
int[] numbers = {10, 20, 30};
for (int i = 0; i < numbers.length; i++) {
    System.out.println(numbers[i]);
}

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🧪 Code Example: Single-Dimensional Array

java
public class ArrayExample {
    public static void main(String[] args) {
        int[] ages = {12, 15, 18, 21};

        // Accessing elements
        System.out.println("First Age: " + ages[0]);

        // Traversing through array
        for (int i = 0; i < ages.length; i++) {
            System.out.println("Age: " + ages[i]);
        }
    }
}

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🧪 Code Example: Multi-Dimensional Array

java
public class MultiDimensionalArrayExample {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };

        // Accessing elements
        System.out.println("Element at [1][1]: " + matrix[1][1]);

        // Traversing a 2D array
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[i].length; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }
    }
}

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📝 Array Initialization

Arrays can be initialized in two ways:

1. Declaration with Initialization:

java
int[] numbers = {1, 2, 3, 4, 5};

2. Declaration with new Keyword:

java
int[] numbers = new int[5];  // Size 5, elements are initialized to 0 by default

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🧑‍🏫 Array Methods (Useful for advanced users)

• Arrays.sort(array): Sorts the array in ascending order.

  java
  int[] numbers = {5, 2, 8, 1};
  Arrays.sort(numbers);
  System.out.println(Arrays.toString(numbers)); // Output: [1, 2, 5, 8]
  

• Arrays.toString(array): Converts an array into a string representation.

  java
  int[] numbers = {1, 2, 3, 4};
  System.out.println(Arrays.toString(numbers)); // Output: [1, 2, 3, 4]
  

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📊 Summary Table

Array Type	Example	Access
1D Array	int[] numbers = {1, 2, 3};	numbers[0]
2D Array	int[][] matrix = {{1,2},{3,4}};	matrix[1][1]

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