Types of Arrays

Arrays are categorized based on the number of indices used to access elements.

A. One-Dimensional Array (1D)

A One-Dimensional Array (or 1D Array) is the simplest form of an array. It is a linear list of elements of the same type, stored in contiguous memory locations. You can imagine it as a single row of lockers, where each locker has a unique index number. Java Implementation

public class OneDimensionalArray {
    public static void main(String[] args) {
        // 1. Static Initialization (Declaration + Creation + Assignment)
        // Used when we already know the data
        int[] marks = {85, 90, 78, 92, 88}; 
        
        System.out.println("First student's mark: " + marks[0]); // Accessing index 0

        // 2. Dynamic Initialization (Declaration + Memory Allocation)
        // Used when we don't know the values yet
        String[] fruits = new String[4]; // Creates an empty array of size 4
        
        // Assigning values manually
        fruits[0] = "Apple";
        fruits[1] = "Banana";
        fruits[2] = "Mango";
        fruits[3] = "Orange";

        System.out.println("\nList of Fruits:");
        // Traversal using a for-loop
        for (int i = 0; i < fruits.length; i++) {
            System.out.println("Index " + i + ": " + fruits[i]);
        }
        
        // Traversal using Enhanced For-Loop (For-Each)
        System.out.println("\nMarks:");
        for (int m : marks) {
            System.out.print(m + " ");
        }
    }
}

• Analogy: A row of lockers in a school hallway.
• Use Case: Storing a list of student marks or daily temperatures.

B. Multi-Dimensional Array (2D, 3D)

Arrays within arrays. The most common is the 2D Array (Matrix).

Java Implementation

public class TwoDimensionalArray {
    public static void main(String[] args) {
        // Declaration: int[rows][columns]
        // Example: A 3x3 Matrix
        int[][] matrix = {
            {1, 2, 3}, // Row 0
            {4, 5, 6}, // Row 1
            {7, 8, 9}  // Row 2
        };

        System.out.println("Element at Row 1, Column 2 (Index 1,2): " + matrix[1][2]); // Output: 6

        System.out.println("\nDisplaying the 3x3 Matrix:");
        // Outer loop for Rows
        for (int i = 0; i < matrix.length; i++) {
            // Inner loop for Columns
            for (int j = 0; j < matrix[i].length; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println(); // New line after every row
        }
    }
}

• Analogy: A spreadsheet or a chessboard (Rows and Columns).
• Use Case: Storing an image (pixels), matrices, or tables.