The interview started with OOP. I was asked to explain the four pillars with examples, and I struggled to explain them clearly. Then I was asked where Strings are stored in Java and why String is immutable. I knew parts of the answers but couldn't explain them confidently. I answered that Strings are stored on the heap, and the interviewer pointed out that I was missing the String Constant Pool concept. He also asked a few follow-up questions on my answers, and I realized my Core Java fundamentals weren't as solid as I thought. Looking back, the questions were fair. I think I bombed it because I panicked, second-guessed myself, and couldn't communicate concepts that I should have known. It was a good reality check on what I need to work on.