java.net.URLConnection.getFileNameMap() loads a table of MIME mappings from either a user specified file identified by the "content.types.user.table" system property or a default location. This MIME table is used then in various places such as the simple HTTP server.

It would be useful if the capability were enhanced to load a file which adds entries to the existing default. This could include the capability to override existing (default) entries if they are no longer correct.

It could work by using the existing property name with a "+" character prefix (to the value) maybe to indicate augmenting the default file with additional entries from the indicated file (minus the prefix).