Java Program to Count Number of Vowels in a String

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Java Program to Count Number of Vowels in a String | The alphabets ‘A’, ‘E’, ‘I’, ‘O’, ‘U’ (in uppercase) and ‘a’, ‘e’, ‘i’, ‘o’, ‘u’ are vowels and remaining alphabets are called consonants.

The given String can be in uppercase or lowercase or both, so either we have to write separate logic for both cases or convert the given string to uppercase or lowercase and write logic only for one case.

In String class, toUpperCase() method is given to convert the given string to uppercase, and toLowerCase() method is given to convert string to lowercase.

// convert string to uppercase
String str = "[email protected]";
str = str.toUpperCase();

The toUpperCase() method converts “[email protected]” to “[email protected]”. Therefore, we have to write logic to check only for ‘A’, ‘E’, ‘I’, ‘O’, ‘U’. The charAt(int i) method of String class can be used to iterate through the each character of the String.

Condition to check character is vowel or not,

// in case of uppercase characters
if(ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U')
then it is vowel.

// in case of lowercase characters
if(ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u')
then it is vowel.

To count the number of vowels in the given String take a “count” variable of int data type and check each character. If any character is vowel then increase the “count” variable by 1. Finally, the count value has the total numbers of vowel in the given String.

Program to Count Vowels in Java String

import java.util.Scanner;

public class CountVowels {

   public static void main(String[] args) {
      // declare variables
      Scanner scan = null;
      String str = null;
      int countVowel = 0;

      // create Scanner class object
      scan = new Scanner(System.in);

      // read input
      System.out.print("Enter String:: ");
      str = scan.nextLine();

      // convert string to upperCase
      str = str.toUpperCase();

      // check each character
      for(int i=0; i < str.length(); i++) {
         if(isVowel(str.charAt(i)))
            countVowel++;
      }

      // display result
      System.out.println("Number of vowels:: "
                   + countVowel);

      // close Scanner object
      scan.close();
   }

   // method to check vowel (only uppercase)
   private static boolean isVowel(char ch) {
      if(ch == 'A' || ch == 'E' || ch == 'I'
                 || ch == 'O' || ch == 'U') {
         return true;
      }
      return false; // else return false;
   }

}

Output:-

Enter String:: [email protected]
Number of vowels:: 3

Enter String:: Hello, How are you?
Number of vowels:: 7

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