When to Throw Exceptions
Question
When should you throw an exception? Is there a downside to exception-driven development?
Short interview answer
Throw for exceptional failure states that the caller cannot handle as normal flow. Do not use exceptions for routine expected outcomes; use validation,
Try*APIs, or explicit results where appropriate.
Detailed answer
An invalid argument or impossible object state may justify a specific exception. A missing optional lookup result usually does not. Exceptions carry stack and allocation costs and make normal control flow harder to read; they also obscure which outcomes callers are expected to handle. A pre-check can still race with the operation, so exceptions may remain necessary even when a condition is checked first.