Use exceptions rather than assertions for handling critical error conditions that need to be caught in production. Assertions should only be used for development-time invariant checking that should never occur in production code. Bad: ```java assert bestAssignment != -1 : "Failed to assign vector to centroid"; ``` Good: ```java if (bestAssignment == -1) { throw new IllegalStateException("Failed to assign vector to centroid"); } ``` Assertions are disabled by default in production environments, which means critical error conditions could be silently ignored. This can lead to data corruption or system instability. Instead: 1. Use exceptions for error conditions that: - Need to be handled by calling code - Represent invalid states that could occur in production - Should trigger error reporting/monitoring 2. Reserve assertions for: - Validating internal implementation invariants - Checking preconditions during development/testing - Documenting assumptions that should never be violated When choosing between exceptions and assertions, ask "Should this error be caught and handled in production?" If yes, use an exception.