The thread 1{{execute interrupt}} command prints the stack of thread ID 1.
thread 1
Arthas supports pipes, and you can find main class with thread 1 | grep 'main('{{execute T2}}.
main class
thread 1 | grep 'main('
You can see that main class is demo.MathGame:
demo.MathGame
$ thread 1 | grep 'main(' at demo.MathGame.main(MathGame.java:17)