025: Effective Java for Android developers : Item 7

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

(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.

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