Here is a java example that generates six letters and check if it consists of any vowel.If vowel exists, it will display the no of vowels.

class GenerateLetters{
    public static void main(String[] args){
        String alphabet="abcdefghijklmnopqrstuvwxyz";
        String st = "";
        String str="";
        int count=0;
        for (int i = 0; i < 6; i++) {
            st += alphabet.charAt((int) (Math.random() * alphabet.length()));
        }
        System.out.println(st);
        for (int i = 0; i < st.length(); i++) {
        char c = st.charAt(i);
        if (c=='a' || c=='e' || c=='i' || c=='o' || c=='u') {
        count++;
        str+=c+" ";
        }
        }
        if(count>1){
        System.out.println("There are" + " " + count + " " + "vowels in the generated string.They are: "+str);
        }
        else{
            System.out.println("String is not having any vowel.");
        }
    }
}