Crack Java Interviews: Count Vowels & Consonants using Java 8 Stream API

April 19, 2026

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Today I have released new video on "Java Interview Question: Check String is Pangram Using Java 8 Streams"

This is frequently asked question in Java Interview.

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package org.practice.basicprgms;

import java.util.List;
import java.util.stream.Collectors;

public class FindTheNumberOfVowelsAndConsonents {

	public static void main(String[] args) {
		String str = "I am Experienced Developer";
		long vowels = 0;
		long consonents = 0;
		
		// 1. Using Count, map and filter
		List<Character> list = 
			str.chars()
				.mapToObj(c -> (char)c)
				.filter(Character::isLetter)
				.collect(Collectors.toList());
		
		vowels =
			str.toLowerCase()
				.chars()
				.mapToObj(c -> (char)c)
				.filter(Character::isLetter)
				.filter(c -> "aeiou".contains(c.toString()))
				.count();
		
		System.out.println("Using Count, map and filter : Vowels : "+ vowels);
		System.out.println("Using Count, map and filter : Consonents : "+ (list.size()-vowels));
		
		
		// 2. Using count second approach
		vowels = 0;
		consonents = 0;
		
		vowels = 
			str.toLowerCase()
				.chars()
				.mapToObj(c -> (char)c)
				.filter(c -> "aeiou".indexOf(c) >= 0)
				.count();
		
		consonents =
			str.toLowerCase()
				.chars()
				.mapToObj(c -> (char)c)
				.filter(Character::isLetter)
				.filter(c -> "aeiou".indexOf(c) == -1)
				.count();
		System.out.println("Using count second approach : Vowels : "+ vowels);
		System.out.println("Using count second approach : Consonents : "+ consonents);
				
		// 3. Using Conditional Operator
		vowels = 0;
		consonents = 0;
		
		vowels = str.toLowerCase()
					.chars()
					.filter(Character::isLetter)
					.map(c -> "aeiouAEIOU".indexOf(c) >= 0 ? 1 : 0)
					.sum();
		
		consonents = str.toLowerCase()
						.chars()
						.filter(Character::isLetter)
						.map(c -> "aeiouAEIOU".indexOf(c) == -1 ? 1 : 0)
						.sum();

		System.out.println("Using Conditional Operator : Vowels : "+ vowels);
		System.out.println("Using Conditional Operator : Consonents : "+ consonents);

		// 4. Using Regular Expression
		vowels = 0;
		consonents = 0;
		
		vowels = str.replaceAll("[^aeiouAEIOU]", "").chars().count();
		consonents = str.replaceAll("[^a-zA-Z]", "").length() - vowels;
		System.out.println("Using Conditional Operator : Vowels : "+ vowels);
		System.out.println("Using Conditional Operator : Consonents : "+ consonents);

		// 5. Using Filtering and Counting
		vowels = 0;
		consonents = 0;
		
		vowels  = str.toLowerCase()
					.chars()
					.mapToObj(c -> (char)c)
					.collect(Collectors.filtering(c -> "aeiou".contains(c.toString()),
							 Collectors.counting()));
		
		consonents = str.toLowerCase()
						.chars()
						.mapToObj(c -> (char)c)
						.filter(Character::isLetter)
						.collect(Collectors.filtering(c -> !"aeiou".contains(c.toString()),
								 Collectors.counting()));
		
		System.out.println("Using Filtering and Counting : Vowels : "+ vowels);
		System.out.println("Using Filtering and Counting : Consonents : "+ consonents);
	}

}

output:
Using Count, map and filter : Vowels : 11
Using Count, map and filter : Consonents : 12
Using count second approach : Vowels : 11
Using count second approach : Consonents : 12
Using Conditional Operator : Vowels : 11
Using Conditional Operator : Consonents : 12
Using Conditional Operator : Vowels : 11
Using Conditional Operator : Consonents : 12
Using Filtering and Counting : Vowels : 11
Using Filtering and Counting : Consonents : 12