java - Clean up code in finalize() or finally()?

Question

I had the general view that clean up of resources is done in the finally block,
recently I found this particular code snippet in a class and it was overriding the Object class' finalize() method.

protected void finalize() {  
    try {
        In.close(); 
        Out.close();
        socket.close();
    }
    catch (Exception e) {
        //logger code here
    }
}

Is this a good idea? What are the pros and cons of finalize() over finally?

Answer 1

The finally block is just a block of code that always executes after a try block, even if there is an exception. i.e. it is local in scope

The finalize() method is an approach for cleaning up the whole object when it is garbage collected.

Java documentation of finalize()

finally solves the problem of cleaning up resources in a block of code regardless of whether an exceptional condition occurs... finalize() is a way to clean up resources when your object is no longer being used, once the Garbage Collecter determines there are no more references to that object.

In short, to answer your question, for example, if the sockets you are closing are members of an object you should close them in the finalize() method, (although that's sub-optimal, and just for example, because there is no guarantee when the GC will actually perform the action)

If however you're opening the socket in a method, and are done with it when the method ends you should free the resources in the finally block.