Fidelity Investments interview questions

Tell me about a time where you faced a bug in your code and your process of resolving it.

The hiring manager asked questions about the resume and some STAR questions. Then, she asked a brief coding question to test my problem-solving skills. I didn't need to write any code. They were okay with pseudocode. The final round was a live coding and core Java questions with 2 principal engineers. One of them was friendly, but the other engineer had a rude tone. They should consider who they should have for interviews. Don't invite them to interviews just because they are principal devs. The live coding was an easy level of string manipulation. What shocked me was that they didn't know what map.getOrDefault() method does. Instead of admitting their lack of knowledge, the rude dev questioned me and said, "this doesn't seem supported in Java". The audacity of asking a coding question and not knowing a basic method is crazy to me. Even when I successfully wrote the code, that guy kept nitpicking and said my code looks okay, but there are other ways to write it. I mean, no shoot Sherlock. I asked him what other way he'd write, and he said he would use Streams instead of a loop, as if that makes the algorithm different. Maybe because I used to work for SV companies, but they didn't seem knowledgeable for principal-level engineers.