Regularly scheduled updates to each release contain fixes for a set of critical bugs identified since the initial release of the platform.
When an update release becomes available, it becomes the default download at the Java SE Downloads page.
The download site includes a link to the release notes that list the bug fixes in the release. Each bug in the list is linked to the bug description in the bug database. The release notes also includes the list of fixes in previous update releases. If you encounter an issue, or suspect a bug, then, as an early step in the diagnosis, check the list of fixes that are available in the most recent update release.
Sometimes, it is not obvious if an issue is a duplicate of a bug that was already fixed.
