I noticed on Rogers Cadenhead's blog that he was looking for, and found, how to get an MD5 hash for a password in Java. Of course, like so many things it's "right there" in the Java libraries, but you have to know where to look! MessageDigest, in this case. I have a trivially small class that I use to wrap the ugliness. Typically, you just want to either check that a clear text password you've been given hashes to match a stored value, or you want to hash that string to get a value you can store. So that's just two very simple function APIs, and here's how I wrap them into a little class:

import java.security.*;

public class MD5Password
  {
  public static String getEncodedPassword(String clearTextPassword)
               throws NoSuchAlgorithmException
    {
    MessageDigest md = MessageDigest.getInstance("MD5");

    md.update(clearTextPassword.getBytes());

    return HexString.bufferToHex(md.digest());
    }

  public static boolean testPassword(String clearTextTestPassword,
                     String encodedActualPassword)
                     throws NoSuchAlgorithmException
    {
    String encodedTestPassword = MD5Password.getEncodedPassword(
                      clearTextTestPassword);

    return (encodedTestPassword.equals(encodedActualPassword));
    }
  }

If you really wanted to assume that NoSuchAlgorithmException would never be thrown, you could have these functions catch it and eat it, or catch it and rethrow as an unchecked exception.