Are resources closed before or after the finally?

Question

In Java 7's try-with-resources, I don't know which order the finally block and the auto-closing happens. What's the order?

BaseResource b = new BaseResource(); // not auto-closeable; must be stop'ed
try(AdvancedResource a = new AdvancedResource(b)) {

}
finally {
    b.stop(); // will this happen before or after a.close()?
}

Quinone

Answer 1

The resource gets closed before catch or finally blocks. See this tutorial.

A try-with-resources statement can have catch and finally blocks just like an ordinary try statement. In a try-with-resources statement, any catch or finally block is run after the resources declared have been closed.

To evaluate this is a sample code:

class ClosableDummy implements Closeable {
    public void close() {
        System.out.println("closing");
    }
}

public class ClosableDemo {
    public static void main(String[] args) {
        try (ClosableDummy closableDummy = new ClosableDummy()) {
            System.out.println("try exit");
            throw new Exception();
        } catch (Exception ex) {
            System.out.println("catch");
        } finally {
            System.out.println("finally");
        }


    }
}

Output:

try exit
closing
catch
finally

Philia

Crazy. So Try-with-resources is no good replacement for try-catch-finally when the resource is needed to handle the catch. – Ornithorhynchus

Resources don't needs handling in catch block. – Philia

The catch block may need the resource to complete it's task. – Ornithorhynchus

This is bad. I thought I could call rollback() in finally while using try-with-resources on an SQL connection. This way, I can't. See also https://mcmap.net/q/390791/-does-java-connection-close-rollback – Barthol

Answer 2

According to the JLS 13; 14.20.3.2. Extended try-with-resources

The finally block is the last to be executed:

Furthermore, all resources will have been closed (or attempted to be closed) by the time the finally block is executed, in keeping with the intent of the finally keyword.

Bodnar