codestyle; put javadoc before or after annotation?

Before the annotation, since the annotation is code that “belongs” to the class.
See examples with javadoc in the official documentation.

Here’s a random example I found in another official Java page:

/**
 * Delete multiple items from the list.
 *
 * @deprecated  Not for public use.
 *    This method is expected to be retained only as a package
 *    private method.  Replaced by
 *    {@link #remove(int)} and {@link #removeAll()}
 */
@Deprecated public synchronized void delItems(int start, int end) {
    ...
}