Java program to print the vowels in a string

Java program to print the vowels in a string:

This Java program will print all the vowels in a string. With this example, you will learn how to iterate over the characters of a string, how to check if a character is vowel or not and how to print all the vowels.

I will show you two different ways to write this program.

Method 1: Iterate and find the vowels:

With this example, the program will iterate over the characters and find out all vowels of the string. It will print these vowels one by one.

import java.util.Scanner;

class Main {
    private static boolean isVowel(char c) {
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'
                || c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U';
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("Enter a string: ");
        String str = scanner.nextLine();

        System.out.println("Vowels found: ");
        for (char c : str.toCharArray()) {
            if (isVowel(c)) {
                System.out.print(c + " ");
            }
        }
    }
}

Here,

The isVowel method is used to check if a character is a vowel or not. It takes a character as its parameter and returns one boolean value. It compares the character with both uppercase and lowercase vowels. It returns true if the character c is a vowel and false otherwise.
The scanner object reads the user input. It reads the user input string and assigns it to the str variable.
The for loop iterates over the character of the string one by one and it calls the isVowel method to check if the current character is a vowel or not. If it is a vowel, it prints the character.

If you run this program, it will print output as below:

Enter a string: 
Hello World
Vowels found: 
e o o 

Enter a string: 
Hello Universe
Vowels found: 
e o U i e e

Method 2: Remove duplicate characters:

In the above example, it prints all the characters found. It doesn’t check if the same character was printed before. We can use a HashSet to remove duplicate characters. Let me change the above example to use HashSet:

import java.util.HashSet;
import java.util.Scanner;

class Main {
    private static boolean isVowel(char c) {
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'
                || c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U';
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        HashSet<Character> characterSet = new HashSet<>();

        System.out.println("Enter a string: ");
        String str = scanner.nextLine();

        System.out.println("Vowels found: ");
        for (char c : str.toCharArray()) {
            if (isVowel(c)) {
                characterSet.add(c);
            }
        }

        characterSet.forEach(c -> System.out.print(c + " "));
    }
}

We made a few changes to the program.

One HashSet object is created to add the vowels.
In the for loop, the vowels are added to the HashSet. The HashSet class provides a method called add() to add an item. It will not add any duplicate characters.
The last line is iterating over the HashSet and printing its content.

Sample output:

CodeVsColor

Java program to print the vowels in a string