Exception Chaining & Stack Traces

ClassNotFoundException is a checked exception from dynamic class loading (Class.forName) when the class is not found, while NoClassDefFoundError is an Error thrown when a class that existed at compile time is missing or failed to initialize at runtime.

Exception chaining wraps a low-level exception inside a domain-meaningful one using the cause constructor, preserving the original via getCause() and the Caused by chain in stack traces.

A stack trace shows the complete call chain with class, method, file, and line number for each frame, and must be logged correctly using log.error("msg", exception) with the throwable as the last argument.

fillInStackTrace() captures the full call stack on every exception creation, costing 1 to 5 microseconds, and can be overridden to return this for stackless exceptions that are 100 times cheaper.