These days which tool is hot??
When i am undergraduate,  java and c++ is most wanted.
How about these days???

C++ is still really loved, lot of people also talk about rust

C & C++ aren't going away any time soon, certainly all desktop OS work is done in those two (Linux kernel is written in C, Windows is more C++ these days). Java has found a platform in Android, used to be mainly for the web but after browsers stopped supporting applets, that fell by the wayside.

Python seems to be used quite a lot in teaching & I've seen it used quite a bit for AI. Not sure it's that viable for proper applications though.