Trying MD5 Hash in java

Hi I have written a class to create a hash for a String input but my Program sometimes give same hash for two different input.

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;


public class Test {

public byte[] Hash(String input) throws NoSuchAlgorithmException
{
    MessageDigest messageDigest = MessageDigest.getInstance("MD5");
    byte b[] = messageDigest.digest(input.getBytes());
    return b;
}

public static void main(String args[]) throws NoSuchAlgorithmException
{
   Test t = new Test();
   byte[] hashValue = t.Hash("viud");
   String hashString = hashValue.toString();
   while(hashString.length()<32)
   {
       hashString = "0" + hashString;
   }
   System.out.println(hashString);
}

}

When my input to the function Hash() is "viud" the I am getting result as --> 0000000000000000000000[B@13e8c1c And when my input String is "Hello" then also I am getting result as --> 0000000000000000000000[B@13e8c1c

But this case is happening only few times on program execution. Every time I am running the Program,I am getting different hash generated for the same input value and also sometimes getting same hash value for two different inputs.

What happens exactly??

   byte[] hashValue = t.Hash("viud");
   String hashString = hashValue.toString();

toString on a byte[] will give you the memory (heap) address of the byte[]. This isn't what you want. You want

String hashString = new String(t.Hash("viud"));