Observed two demon threads are part of static block and are started at class initialization. Starting the threads lazily—only when needed—will reduce loading time and improve performance.

Those were lazy before the JDK-8351907 change. Now it can be triggered not only from robot calls which are using those threads, but also from the XToolkit:

https://github.com/openjdk/jdk/commit/2dfbf41d2a3dbcd44f9ed9a58a1b0932d7536977#diff-bc685def01d3c123e569dec4b2dfe03163da3853321e94d2fa81f93e049412c2R1526

It is enabled by default for Gnome 47+

https://github.com/openjdk/jdk/commit/2dfbf41d2a3dbcd44f9ed9a58a1b0932d7536977#diff-646090ace444ea9d9d877827cfcb16875bfdf34e4fd772a1534ef6e97c8698ceR60