What are the performance and correctness costs of exceptions, and why shouldn't you use them for control flow?

Constructing an exception captures a full stack trace (fillInStackTrace), which is the expensive part, so throwing exceptions on a hot path for normal outcomes is a real performance hit and obscures actual errors.

Using exceptions for control flow (e.g., catching to break a loop) is both slow and unreadable; return an Optional, a result type, or a sentinel for expected 'not found' cases. If you must signal a frequent expected condition via exception, you can override fillInStackTrace to skip the trace.