Java Program to Count Number of Vowels in a String
Last Updated :
02 Nov, 2022
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:
- Iterative
- 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.
Below is the implementation of the above approach:
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();
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);
}
}
OutputTotal 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 substrings to return the answer recursively, we will get the answer for the string starting from the 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)
Below is the implementation of the above approach:
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()));
}
}
OutputTotal number of vowels in string are:
6
Method 3: Using ArrayList and contains() method
Java
// Java Program to Count Number of Vowels
// in a String
import java.io.*;
import java.util.*;
public class Main{
public static void main(String[] args)throws IOException
{
String str = "GeeksForGeeks";
str = str.toLowerCase();
int count = 0;
String vow ="aeiou";
ArrayList<Character> vowels = new ArrayList<Character>();
for(int i=0;i<vow.length();i++)
{
vowels.add(vow.charAt(i));
}
for (int i = 0; i < str.length(); i++) {
if(vowels.contains(str.charAt(i))){
count++;
}
}
// display total count of vowels in string
System.out.println("Total no of vowels in string are: " + count);
}
}
OutputTotal no of vowels in string are: 5
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