googlecode.com is no longer in service. Thus using javadoc on Google Guava classes always results in a 404 error page.

The change proposed here updates the URL to point to the current release of Guava, release 23.0.

Unfortunately, the new URL contains the release version, so will be out-of-date soon as Guava has a higher release cadence (and there can be breakage). The alternative is to simply drop support for Guava in javadoc.