JavaAlgorithms/Strings/CheckVowels.java

package Strings;

/**
 * Vowel Count is a system whereby character strings are placed in order based on the position of
 * the characters in the conventional ordering of an alphabet. Wikipedia:
 * https://en.wikipedia.org/wiki/Alphabetical_order
 */
class CheckVowels {
  public static void main(String[] args) {
    assert !hasVowels("This is a strings");
    assert hasVowels("Hello World");
    assert hasVowels("Java is fun");
    assert !hasVowels("123hi");
    assert hasVowels("Coding vs Programming");
  }

  /**
   * Check if a string is has vowels or not
   *
   * @param input a string
   * @return {@code true} if given string has vowels, otherwise {@code false}
   */
  public static boolean hasVowels(String input) {
    if (input.matches("[AEIOUaeiou]")) {
      countVowels(input);
      return true;
    }
    return false;
  }
  /**
   * count the number of vowels
   *
   * @param input a string prints the count of vowels
   */
  public static void countVowels(String input) {
    input = input.toLowerCase();
    int count = 0;
    int i = 0;
    while (i < input.length()) {
      if (input.charAt(i) == 'a'
          || input.charAt(i) == 'e'
          || input.charAt(i) == 'i'
          || input.charAt(i) == 'o'
          || input.charAt(i) == 'u') {
        count++;
      }
      i++;
    }
    System.out.println(count);
  }
}