Energy One Senior Java Developer interview questions

The first step is to write a small Java program. The development manager sent me the problem via email. He said it should take one+ hour. I spent 5 hours on it and send him my code the next day. My code did miss some cases and it led to non-procession. My advice: The question did not provide much test cases. You'd better think carefully about possible failing cases before you believe your code is correct!