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Java Program to Count Number of Vowels in a String

  • Last Updated : 07 Jan, 2021

In java, the string is a sequence of characters and char is a single digit used to store variables. The char uses 2 bytes in java. In java, BufferedReader and InputStreamReader are used to read the input given by the user from the keyboard. Then readLine() is used for reading a line. The java.io package in java provides input and output through data streams, serialization, and the file system.

We can count the vowels in a string in two ways:

  1. Iterative
  2. Recursive

Examples:

Input: GeeksForGeeks
Output: Total no of vowels in string are: 5

Input: ChETaN
Output: Total no of vowels in string are: 2

Method 1: Iterative 

Approach:



  • We will traverse through the string’s characters in a for loop starting from index 0 till size-1.
  • And check each character if it is a vowel or not and increment the count variable.

Java




// Java Program to Count Number of Vowels
// in a String in a iterative way
  
import java.io.*;
  
public class vowel {
    public static void main(String[] args)
        throws IOException
    {
        String str = "GeeksForGeeks";
  
            str = str.toLowerCase();
  
        // toCharArray() is used to convert 
        // string to char array
        char[] chars = str.toCharArray();
  
        int count = 0;
  
        for (int i = 0; i < str.length(); i++)
        {
            // check if char[i] is vowel
            if (str.charAt(i) == 'a' || str.charAt(i) == 'e'
                || str.charAt(i) == 'i'
                || str.charAt(i) == 'o'
                || str.charAt(i) == 'u')
            {
                // count increments if there is vowel in
                // char[i]
                count++;
            }
        }
  
        // display total count of vowels in string
        System.out.println("Total no of vowels in string are: " + count);
    }
}
Output
Total no of vowels in string are: 5

Method 2: Recursive

Approach:

  • Check for the base condition if the length of the string is 1, then simply check for that single character if it is a vowel, then return 1 else return 0.
  • For dividing the whole string into substring to return the answer recursively, we will get the answer for the string starting from first till second last character.
  • And finally return the above answer plus the answer for the check of last character (1 if it is vowel or 0 if it is not)

Java




// Java Program to Count Number of Vowels
// in a String in a recursive way
  
import java.io.*;
  
class GFG {
  
    // isVowel() function returns 1 if the
    // character is a vowel and 0 if it is not
    static int isVowel(char chars)
    {
        if (chars == 'a' || chars == 'e' || chars == 'i'
            || chars == 'o' || chars == 'u') {
            return 1;
        }
        else {
            return 0;
        }
    }
  
    // recursive function to return the number
    // of characters in a string
    static int vowelno(String str, int l)
    {
        if (l == 1) {
            return isVowel(str.charAt(l - 1));
        }
  
        return vowelno(str, l - 1)
            + isVowel(str.charAt(l - 1));
    }
  
    public static void main(String[] args)
        throws IOException
    {
        String str = "BufferedOutput";
  
        str = str.toLowerCase();
  
        System.out.println(
            "Total number of vowels in string are:");
  
        System.out.println(vowelno(str, str.length()));
    }
}
Output
Total number of vowels in string are:
6

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