Java Arrays

Welcome to The Coding College! In this tutorial, we’ll dive into Java Arrays, a fundamental concept for managing and storing data efficiently in programming. Arrays allow you to store multiple values in a single variable, simplifying the process of working with large datasets.

What is an Array?

An array is a data structure that can hold a fixed number of elements of the same type.

  • The elements in an array are stored at contiguous memory locations.
  • Each element is accessed using an index, starting from 0.

Syntax

dataType[] arrayName; // Declares an array
arrayName = new dataType[size]; // Allocates memory for the array

Alternatively, you can combine the declaration and allocation:

dataType[] arrayName = new dataType[size];

Example: Creating and Initializing an Array

public class ArrayExample {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50}; // Array initialization
        for (int i = 0; i < numbers.length; i++) {
            System.out.println("Element at index " + i + ": " + numbers[i]);
        }
    }
}

Output

Element at index 0: 10  
Element at index 1: 20  
Element at index 2: 30  
Element at index 3: 40  
Element at index 4: 50

Types of Arrays

1. Single-Dimensional Array

A single-dimensional array is a linear collection of elements.

Syntax

dataType[] arrayName = new dataType[size];

Example

public class SingleDimensionalArray {
    public static void main(String[] args) {
        String[] fruits = {"Apple", "Banana", "Cherry"};
        for (String fruit : fruits) {
            System.out.println(fruit);
        }
    }
}

2. Multi-Dimensional Array

A multi-dimensional array stores data in rows and columns, resembling a matrix.

Syntax

dataType[][] arrayName = new dataType[rows][columns];

Example

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

        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();
        }
    }
}

Output

1 2 3  
4 5 6  
7 8 9

Common Operations on Arrays

1. Access Elements

Access elements using their index:

int element = arrayName[index];

2. Update Elements

Modify the value at a specific index:

arrayName[index] = newValue;

3. Find Length of an Array

Use the length property:

int length = arrayName.length;

4. Iterate Over an Array

Using a for Loop

for (int i = 0; i < arrayName.length; i++) {
    System.out.println(arrayName[i]);
}

Using a for-each Loop

for (dataType element : arrayName) {
    System.out.println(element);
}

Practice Problems

  1. Write a program to find the largest and smallest numbers in an array.
  2. Create a two-dimensional array to store and display a multiplication table.
  3. Reverse the elements of an array and print the result.

Key Points

  • Arrays in Java are zero-indexed.
  • The size of an array is fixed once defined.
  • Use arrays to store and manipulate collections of similar data efficiently.

For more tutorials and coding tips, visit The Coding College. Stay consistent and keep coding your way to success! 🚀

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