Okay,
I've downloaded "flashtool-0.9.18.5-linux.tar.7z" from the Xda Forums ( http://xda-forum.blogspot.nl/2015/03/how-to-install-xperia-firmware-using.html ) and I have tried to run "x10flasher.jar" contained therein by double-clicking it, by selecting "Open with OpenJDK Java 7 Runtime" and by selecting "Open with Oracle 7 Java Runtime" (after selecting "Properties-->Permissions-->Allow executing file as a program" first, of course), however none of these actions does anything.
So, back to the beginning.
Then I tried extracting flashtool-0.9.18.5-linux.tar.7z (so I now have "flashtool-0.9.18.5-linux.tar.7z" and "flashtool-0.9.18.5-linux.tar" on my Desktop) and following the instructions at How do I install Flashtool 0.91 on Ubuntu 14.04 LTS? ...
When I type:
cd Desktop
Termianl tells me:
bash: cd: FlashTool: No such file or directory
When I extract "flashtool-0.9.18.5-linux" (so I now have "flashtool-0.9.18.5-linux.tar.7z", "flashtool-0.9.18.5-linux.tar" and "FlashTool" (folder) on my Desktop) and then type:
cd FlashTool
Everything seems to go fine, but then when I type:
./ FlashTool
Terminal tells me:
bash: ./: Is a directory
I suspect the problem and the resolution is something simple, but whatever the problem and the solution is, I just can't seem to nail it... Any help would be appreciated.