Does anybody know a reliable hashCode-function for strings?

Question

Hello,
I would like to exchange hashcodes between clients and server, both running at different jre's (even msjvms are running it) - and for the same string they should be identical.
Javadoc mentions that Object.hashCode() may vary from imlpementation, but I would need an implementation which would be consistent across jvms.
Does anybody know a reliable function which does compute a integer-hash-value out of string?
Reliable means that its quite unlikely that two different strings get the same hash-value (although I know this cannot be guaranteed 100%).
Thanks in advance, lg Clemens

Answer 1

Even the hashcode() API points out that
it is just a suggestion that it returns the memory
address of an object, an implementation that might
differ from other JVMs. So if you'd rely on that
behaviour, you'd need to check JVM vendors as well.True, and that is why you shouldn't rely on the fact that Object.hashCode returns the memory address, but I think it's safe to rely on the fact that String.hashCode returns the same hashCode on all platforms (if they are using the same Java version).
The javadoc for String.hashCode says:
     * Returns a hash code for this string. The hash code for a
     * <code>String</code> object is computed as
     * <blockquote><pre>
     * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
     * </pre></blockquote>
     * using <code>int</code> arithmetic, where <code>s</code> is the
* <i>i</i>th character of the string, <code>n</code> is the length of
* the string, and <code>^</code> indicates exponentiation.
* (The hash value of the empty string is zero.)
* @return a hash code value for this object.
So that contract must be fulfilled by all implementations.
Kaj