Finalizador

Finalizador is a programming concept referring to a routine that runs cleanup code when an object is slated for destruction. In languages with garbage collection, a finalizador is a method or mechanism by which the runtime attempts to release resources that are not managed by the language itself, such as native handles, file descriptors, or unmanaged memory. The term is closely related to, but not identical with, a destructor, which in some languages denotes deterministic destruction.

Timing and guarantees: Finalizadores are generally non-deterministic. The runtime decides when to run them, and there is no guaranteed order or timing for their execution. Because of this, finalizers should not be relied upon for timely release of scarce resources, and they are typically treated as a safety net rather than the primary cleanup mechanism. They may also introduce overhead or risk of resurrecting objects during finalization.

Language patterns and examples: In Java, a finalizer method named finalize() can be defined, but it has been deprecated in favor of explicit resource management through try-with-resources and AutoCloseable. In C#, finalization is implemented via a destructor, written as ~ClassName(), and runs non-deterministically after disposal; the common pattern is to implement IDisposable and call GC.SuppressFinalize when cleaning up. In Python, __del__ serves as a finalizer, but its invocation is subject to reference counting and garbage collection, making deterministic cleanup unreliable. Context managers (with statements) provide deterministic cleanup in many languages.

Best practices: Prefer explicit, deterministic cleanup whenever possible (Dispose/close/exit patterns, using blocks, context managers). Use finalizers only as a fallback for unmanaged resources and keep them minimal and safe. Be wary of resurrection, cross-references to other objects, and code that may block or perform I/O during finalization.

See also: destructor, garbage collection, IDisposable, AutoCloseable, context manager.