how to generate minecraft hex digests in java

package com.serverid;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class ServerID
{
    final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();

    public static void main(String[] args)
    {
        // The test values provided on http://wiki.vg/Protocol_Encryption are:
        // sha1(Notch) :  4ed1f46bbe04bc756bcb17c0c7ce3e4632f06a48
        // sha1(jeb_)  : -7c9d5b0044c130109a5d7b5fb5c317c02b4e28c1
        System.out.println(javaHexDigest("Notch"));
        System.out.println(javaHexDigest("jeb_"));
    }

    private static String javaHexDigest(String data)
    {
        MessageDigest digest = null;
          try {
            digest = MessageDigest.getInstance("SHA-1");
            digest.reset();
            digest.update(data.getBytes("UTF-8"));
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        byte[] hash = digest.digest();
        boolean negative = (hash[0] & 0x80) == 0x80;
        if (negative)
            hash = twosCompliment(hash);
        String digests = getHexString(hash);
        if (digests.startsWith("0"))
        {
            digests = digests.replaceFirst("0", digests);
        }
        if (negative)
        {
            digests = "-" + digests;
        }
        digests = digests.toLowerCase();
        return digests;
    }

    public static String getHexString(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        int v;
        for ( int j = 0; j < bytes.length; j++ ) {
            v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }

    private static byte[] twosCompliment(byte[] p)
    {
        int i;
        boolean carry = true;
        for (i = p.length - 1; i >= 0; i--)
        {
            p[i] = (byte)~p[i];
            if (carry)
            {
                carry = p[i] == 0xFF;
                p[i]++;
            }
        }
        return p;
    }
}