Your question (actually
three questions) is off-topic for this site. Ask here when you have a problem that you don't know how to solve; a compiler error message that you don't understand, unexpected behavior of your program, etc. You might have better luck asking what's the point of threads, exceptions, and lambdas on the
software engineering stack exchange, but (a) ask those as separate questions, and (b) show that you've done
some reading on the subject. (e.g., say, "I read that _____, but I don't understand____ because _____.) —
Solomon Slow 20 secs ago