CatchBlock

CatchBlock is a construct used in exception handling to define code that should run when an exception is thrown from a protected region, typically a try block. A catch block specifies the type of exception it can handle and contains statements to respond to the error, which may include logging, cleanup, user messages, or recovery.

When an exception is thrown, control transfers to the first catch block whose type matches the exception. If a matching catch block is found, normal execution resumes inside that block. If no match is found, the exception propagates up the call stack until it is caught or the program terminates. Some languages also provide a finally block, which executes after catch processing whether or not an exception occurred, often used for resource cleanup.

Across languages the exact syntax differs. In Java: try { ... } catch (IOException ex) { ... }. In C#: try { ... } catch (FileNotFoundException ex) { ... }. In JavaScript: try { ... } catch (err) { ... }. In C++: try { ... } catch (const std::exception& e) { ... }. Some languages support multi-catch, allowing a single block to handle multiple exception types, while others require separate catch clauses for each type.

Common considerations include ordering catch blocks from most specific to most general, avoiding catching generic exceptions unless necessary, and rethrowing or wrapping exceptions when appropriate to preserve context. Catch blocks should perform minimal work and delegate complex recovery to higher levels when possible.

See also: exception handling, try block, finally block.