Question

I’ve an object with a certain state. The object is passed around and it’s state is temporarly altered. Something like:

public void doSomething(MyObject obj) {
    obj.saveState();
    obj.changeState(...);
    obj.use();
    obj.loadState();
}

In C++ it’s possible to use the scope of an object to run some code when constructing and distructing, like

NeatManager(MyObject obj) { obj.saveState(); }
~NeatManager() { obj.loadState(); }

and call it like

void doSomething(MyObject obj) {
    NeatManager mng(obj);
    obj.changeState();
    obj.use();
}

This simplifies the work, because the save/load is binded with the scope of NeatManager object. Is it possible to do something like this in Java? Is there a way to call a method when the object goes out of the scope it’s been declared in? I’m not talking about finalize() nor “destruction” (garbage collection), I’m interested on the scope.

Thanks

Answer 1

Nope, there’s no such thing. The closest is probably a try/finally block:

try
{
    obj.changeState(...);
    obj.use();
}
finally
{
    obj.loadState();
}

This ensures that loadState() gets called even when an Exception is thrown or there’s an early return.