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Java Program to Check Whether a Character is a Vowel or Consonant

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The English alphabet has five vowels: A, E, I, O and U (in uppercase or lowercase). Every other letter is a consonant. Digits and symbols are neither.

This page shows four ways to check whether a character is a vowel or a consonant in Java.

1. Vowel or Consonant Using if-else

The character is first converted to lowercase with Character.toLowerCase(), so only five comparisons are needed instead of ten.

VowelConsonant.java 
public class VowelConsonant {
    public static void main(String[] args) {
        char[] letters = {'K', 'e', 'U', 'z'};

        for (char ch : letters) {
            char c = Character.toLowerCase(ch);
            if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') {
                System.out.println(ch + " is a vowel.");
            } else {
                System.out.println(ch + " is a consonant.");
            }
        }
    }
}
Output
K is a consonant.
e is a vowel.
U is a vowel.
z is a consonant.

2. Vowel or Consonant with User Input

When the character comes from the user, check that it is a letter first. Otherwise a digit or symbol would be reported as a consonant.

VowelConsonantInput.java 
import java.util.Scanner;

public class VowelConsonantInput {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a character: ");
        char ch = scanner.next().charAt(0);
        scanner.close();

        char c = Character.toLowerCase(ch);
        if (c < 'a' || c > 'z') {
            System.out.println(ch + " is not a letter.");
        } else if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') {
            System.out.println(ch + " is a vowel.");
        } else {
            System.out.println(ch + " is a consonant.");
        }
    }
}
Output 1
Enter a character: e
e is a vowel.
Output 2
Enter a character: R
R is a consonant.
Output 3
Enter a character: 9
9 is not a letter.

3. Vowel or Consonant Using switch

A switch statement can list several labels for the same case. Since Java 14, you can write them in one line separated by commas with the arrow (->) syntax.

VowelConsonantSwitch.java 
public class VowelConsonantSwitch {
    public static void main(String[] args) {
        char[] letters = {'K', 'e', 'O', 'b'};

        for (char ch : letters) {
            switch (Character.toLowerCase(ch)) {
                case 'a', 'e', 'i', 'o', 'u' -> System.out.println(ch + " is a vowel.");
                default -> System.out.println(ch + " is a consonant.");
            }
        }
    }
}
Output
K is a consonant.
e is a vowel.
O is a vowel.
b is a consonant.

4. Vowel or Consonant Using a Method

The check can be moved into a reusable method. "aeiouAEIOU".indexOf(ch) returns the position of the character in the string, or -1 if it is not there.

VowelConsonantMethod.java 
public class VowelConsonantMethod {

    static boolean isVowel(char ch) {
        return "aeiouAEIOU".indexOf(ch) != -1;
    }

    public static void main(String[] args) {
        String word = "Java";

        for (char ch : word.toCharArray()) {
            System.out.println(ch + " is a " + (isVowel(ch) ? "vowel" : "consonant") + ".");
        }
    }
}
Output
J is a consonant.
a is a vowel.
v is a consonant.
a is a vowel.

5. Summary

  • A, E, I, O and U are vowels; every other letter is a consonant.
  • Convert the character to lowercase first to halve the number of comparisons.
  • Check that the input is a letter, otherwise digits and symbols look like consonants.
  • A switch with several labels, or "aeiouAEIOU".indexOf(ch), keeps the check short.

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