System.exit() results unexecutable finally block

java try-catch-finally system.exit
Suresh Atta picture Suresh Atta · Feb 16, 2013 · Viewed 7.2k times · Source

I am working on My application's under maintanace module

try {
    if (isUndermaintanace) {
        System.exit(1);
    } else {
        prepareResources();
    }           
} catch (Exception e) {
    printStack(e);
} finally {
    cleanResources();
}

When I am passing isundermaintanace true finally not executing.

What am I missing? Is there any other way to do that?

Answer

Corbin picture Corbin · Feb 16, 2013

Finally's don't execute if you kill the VM (or if the VM dies some other way). System.exit() is a rather crude method of killing the program, whereas finally is a high level OOP concept. System.exit() bails very quickly, doing as little cleanup as possible.

If you went into task manager and killed the process or issued a kill -9 on the process would you expect a finally to execute? It's vaguely (very vaguely) the same thing.

There's a few things worth noting. In particular, I lied a bit in the first part of the post. It's misleading to liken System.exit() to truly instantly killing a program. In particular, shutdown hooks are ran, and if configured, finalizers can actually be ran. Note, however, that the docs fairly strongly suggest against using runFinalizersOnExit.

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