采用indexOf()方法判断

import java.io.*;
public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
        String str = null;
        String target = "AEIOUaeiou";
        while((str = br.readLine()) != null) {
            char ch = str.charAt(0);
            if (target.indexOf(ch) != -1) {
                System.out.println("Vowel");
            } else {
                System.out.println("Consonant");
            }
        }
        br.close();
    }
}