open fds at start: 8
after 50 fully consumed, unclosed Files.walk:  +0 fds
after 50 unclosed Files.lines + findFirst():   +50 fds
after closing them:                           +0 fds
after 50 try-with-resources Files.lines:      +0 fds
after 50 unclosed Files.walk + findFirst():   +300 fds
after closing them:                           +0 fds
after 50 unreferenced, unclosed Files.lines:   +50 fds
after System.gc():                            +0 fds
after 50 unreferenced, unclosed Files.walk:   +300 fds
after System.gc():                            +300 fds