It could be useful to make it possible for a custom handler to request that the connection be closed after an exchange, by supplying "Connection: close" to the response headers. This can be useful to free up resources in the case where the application's logic knows that the connection will no longer be needed.

See: https://mail.openjdk.java.net/pipermail/net-dev/2019-January/012162.html
(and followup: http://mail.openjdk.java.net/pipermail/net-dev/2019-February/012164.html)