public class Vowels2 {
    public static void main(String[] args) {
        System.out.println("a is vowel? " + isVowel("a"));
        System.out.println("z is vowel? " + isVowel("z"));
        
        System.out.println("a is nonvowel? " + isNonVowel("a"));
        System.out.println("z is nonvowel? " + isNonVowel("z"));                       
       
    }
    
    // This method returns whether or not the given string is a vowel.
    // This method uses "Boolean Zen".
    public static boolean isVowel(String s) {
        return s.equalsIgnoreCase("a")
            || s.equalsIgnoreCase("e")
            || s.equalsIgnoreCase("i")
            || s.equalsIgnoreCase("o")
            || s.equalsIgnoreCase("u");
    }
    
    public static boolean isNonVowel(String s) {
        return !s.equalsIgnoreCase("a")
            && !s.equalsIgnoreCase("e")
            && !s.equalsIgnoreCase("i")
            && !s.equalsIgnoreCase("o")
            && !s.equalsIgnoreCase("u");    
    }
}