Java Program to Count the Number of Vowels in a String

Introduction

Counting the number of vowels in a string is a common task in text processing. In Java, this exercise helps you understand how to manipulate strings and use loops or regular expressions. This guide will walk you through writing a Java program that counts the number of vowels in a given string.

Problem Statement

Create a Java program that:

• Prompts the user to enter a string.
• Counts the number of vowels (a, e, i, o, u) in the string, regardless of case.
• Displays the count of vowels.

Example:

• Input: "Hello World"
• Output: Number of vowels: 3

Solution Steps

1. Read the String: Use the Scanner class to take the string as input from the user.
2. Initialize a Vowel Counter: Create a variable to store the count of vowels.
3. Iterate Through the String: Loop through each character in the string and check if it is a vowel.
4. Count the Vowels: Increment the counter each time a vowel is found.
5. Display the Vowel Count: Print the total count of vowels.

Java Program

// Java Program to Count the Number of Vowels in a String
// Author: https://www.rameshfadatare.com/

import java.util.Scanner;

public class VowelCounter {
    public static void main(String[] args) {
        // Step 1: Read the string from the user
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String input = scanner.nextLine();
        
        // Step 2: Initialize the vowel counter
        int vowelCount = 0;
        
        // Step 3: Iterate through the string
        for (int i = 0; i < input.length(); i++) {
            char ch = input.charAt(i);
            
            // Step 4: Check if the character is a vowel
            if (isVowel(ch)) {
                vowelCount++;
            }
        }
        
        // Step 5: Display the vowel count
        System.out.println("Number of vowels: " + vowelCount);
    }
    
    // Helper method to check if a character is a vowel
    public static boolean isVowel(char ch) {
        ch = Character.toLowerCase(ch);
        return ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u';
    }
}

Explanation

Step 1: Read the String

• The Scanner class is used to read a string input from the user. The nextLine() method captures the entire line as a string.

Step 2: Initialize the Vowel Counter

• A simple integer variable vowelCount is initialized to zero. This will hold the count of vowels found in the string.

Step 3: Iterate Through the String

• A for loop is used to iterate over each character in the string, using the charAt() method to access individual characters.

Step 4: Check if the Character is a Vowel

• The isVowel() method is a helper function that checks if a given character is a vowel. It converts the character to lowercase to handle case-insensitivity.

Step 5: Display the Vowel Count

• The program prints the total number of vowels found in the string using System.out.println().

Output Example

Example:

Enter a string: Hello World
Number of vowels: 3

Conclusion

This Java program demonstrates how to count the number of vowels in a user-input string. It covers essential concepts such as string manipulation, loops, and conditionals, making it a valuable exercise for beginners learning Java programming.