public class PoC
{
   public static void main(String[] args)
   {
      /* # INITIALIZE VARIABLES */
      String   sString        = "";
      Integer  sLength        = 0;
      Integer  sLengthVocals  = 0;
      String   sVocals[]      = new String[5];
 
      /* # INITIALIZE ARRAY WITH VOWELS */
      sVocals[0] = "a";
      sVocals[1] = "e";
      sVocals[2] = "i";
      sVocals[3] = "o";
      sVocals[4] = "u";
 
      /* # STRING SET */
      sString = "shellrootin";
 
      /* # FIND NUMBER OF CHARACTERS  */
      sLength = sString.length();
 
      /* # FIND NUMBER OF VOWELS */
      for( int i = 0; i < sLength; i++ )
      {
         for( int j = 0; j < sVocals.length; j++ )
         {
            if( sVocals[j].equals(sString.substring(i, i+1)) )
            {
               sLengthVocals = sLengthVocals + 1; break;
            }
         }
      }
      System.out.println( "String:\t\t\t" + sString );
      System.out.println( "Length string:\t\t" + sLength );
      System.out.println( "Number of vowels:\t" + sLengthVocals );
   }
}

alex@shellroot:~/Escritorio$ javac PoC.java
alex@shellroot:~/Escritorio$ java PoC
String:			shellrootin
Length string:		11
Number of vowels:	4
alex@shellroot:~/Escritorio$ javac PoC.java
alex@shellroot:~/Escritorio$ java PoC
String:			shell root in
Length string:		13
Number of vowels:	4

/**
 * @(#)Vocales.java
 *
 *
 * @author 1mpuls0
 * @version 1.00 2011/3/21
 */
 
 
public class Vocales {
 
	public static void main(String args[]){
		new Vocales();
	}
 
    public Vocales() {
    	String palabra = "foro.elhacker.net";
    	int numeroVocales = contarVocales(palabra);
    	System.out.println("Se encontraron "+numeroVocales+" vocales en " +palabra);
    }
 
    private int contarVocales(String texto) {
    	int contador = 0;
    	texto = texto.toLowerCase();
 
    	for (int i = 0; i < texto.length(); i++) {
    		char c = texto.charAt(i);
    		if (c=='a' || c=='e' || c=='i' || c=='o' || c=='u') {
    			contador++;
    		}
    	}
    	return contador;
    }
}