public class VowelConsonantCount {
    public static void main(String[] args) {
        String str = "Java Programming";
        int vowels = 0, consonants = 0;
        String vowelSet = "aeiouAEIOU";
        // Scan each character once
        for (char c : str.toCharArray()) {
            if (Character.isLetter(c)) { // skip spaces and punctuation
                if (vowelSet.indexOf(c) != -1) vowels++; // found in the vowel set
                else consonants++; // any other letter is a consonant
            }
        }
        System.out.println("Vowels: " + vowels + ", Consonants: " + consonants);
    }
}

▶ Run Code

Output

Vowels: 5, Consonants: 10

Core Logic

One pass through the string is enough — check each letter against a small set of vowels and bucket it accordingly.

How It Works

1str.toCharArray() converts the string into a char[] so it can be scanned one character at a time.
2Character.isLetter(c) filters out spaces and punctuation, so only actual letters are counted.
3For each letter, vowelSet.indexOf(c) checks whether it appears in "aeiouAEIOU".
4A match increments the vowels counter; anything else increments consonants.
5After the loop, both counters hold the final vowel and consonant totals.

For "Java Programming", the scan finds 5 vowels and 10 consonants.

💡

Key Point: Including both cases in vowelSet (aeiouAEIOU) avoids a separate call to toLowerCase() for every character.

Key Concepts

toCharArray()Character.isLetter()for-each loop

Approach 2: Java Streams

Java

public class VowelConsonantCountStream {
    public static void main(String[] args) {
        String str = "Java Programming";
        String vowelSet = "aeiouAEIOU";

        // Count letters that appear in the vowel set
        long vowels = str.chars()
            .filter(Character::isLetter)
            .filter(c -> vowelSet.indexOf(c) != -1)
            .count();

        // Count letters that don't appear in the vowel set
        long consonants = str.chars()
            .filter(Character::isLetter)
            .filter(c -> vowelSet.indexOf(c) == -1)
            .count();

        System.out.println("Vowels: " + vowels + ", Consonants: " + consonants);
    }
}

▶ Run Code

Output

Vowels: 5, Consonants: 10

Core Logic

The same classification can be expressed as a stream pipeline instead of a loop — filter for letters, then split into vowels and consonants.

How It Works

1str.chars() returns an IntStream of the string's character codes.
2.filter(Character::isLetter) keeps only letters, dropping spaces and punctuation, just like the manual version's check.
3A second .filter() splits the stream into vowels (found in vowelSet) or consonants (not found).
4.count() reduces each filtered stream down to a single long total.

Filtering "Java Programming" twice — once for vowels, once for consonants — produces 5 and 10 respectively.

💡

Key Point: This runs the string through two separate stream pipelines, so for very large strings the single-pass loop is actually more efficient — the stream version trades a bit of performance for readability.

Key Concepts

Streamchars()filter()count()

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