In this mini Fragment, we introduce Joshua’s seventh Item and a momentous end to the first chapter: Avoid finalizers
Stay tuned for more items from our “Effective Java for Android developers” Fragment series.
- If you don’t know what they are, ignorance is bliss. If you know what they are, avoid them!
- Finalizers in Java != destructors in C++ (C++ counterparts to constructors).
- In C++ destructors
- you reclaim resources here (Java has GC)
- you also reclaim non-memory resources (use the try-finally block in Java)
- (unpredicatable amt of time between object becoming unreachable and finalizer being executed) Never do anything time critical in finalizer!
- System.gc + System.runFinalization increase chances – no guarantee
- System.runFinalizersOnExit + Runtime.runFinalizersOnExit are the ones that do – but they are fatally flawed
- Java 7 has try with resources, which is also interesting and auto-closeables. [Android] devs can only dream of these.
- If an uncaught exception is thrown in a finalizer, it is ignored, and the finalization abruptly terminates.
- Severe performance penalty for using finalizers – (one e.g.) time to create and destroy simple object goes from 5.6ns -> 2400ns
- Only valid use: as a safety net or to terminate noncritical native resources.
- [Android] you’re probably better off using Android’s lifecycle methods.