How to generate a checksum for an java object

Question

I'm looking for a solution to generate a checksum for any type of Java object, which remains the same for every execution of an application that produces the same object.

I tried it with Object.hashCode(), but the api says

....This integer need not remain consistent from one execution of an application to another execution of the same application.

Answer 1

public static String getChecksum(Serializable object) throws IOException, NoSuchAlgorithmException {
    ByteArrayOutputStream baos = null;
    ObjectOutputStream oos = null;
    try {
        baos = new ByteArrayOutputStream();
        oos = new ObjectOutputStream(baos);
        oos.writeObject(object);
        MessageDigest md = MessageDigest.getInstance("MD5");
        byte[] thedigest = md.digest(baos.toByteArray());
        return DatatypeConverter.printHexBinary(thedigest);
    } finally {
        oos.close();
        baos.close();
    }
}