Control flow of the try...catch...finally control structure

I have a try...catch...finally block whose catch rethrows the exception:

try
{
    startBombCountdownAndRunAsFastAsYouCan();
}
catch (BombExplodedOnYourFaceException ex)
{
    displayMessage("Hahaha! It blew up on your face!");
    throw ex;
}
finally
{
    cleanFloor();
}

displayMessage("Wow, you pulled it off!");

In this example, I need that cleanFloor() be executed regardless of whether the exception was thrown or not. So the questio开发者_如何学编程n is: Is the finally clause always executed, regardless of whether the exception is rethrown in the corresponding catch clause?

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Yes, this is the exact purpose that the finally concept was created.

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Yes, the finally block will always be executed.

Also, as a side note if you're not going to use the explicitly caught exception, you should just use "catch { ... throw; }.

For reference:

http://www.codeproject.com/KB/architecture/exceptionbestpractices.aspx

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The finally is usually executed, but not always.

Consider the following Java program, where the finally block is not executed:

package test;
public class TestFinally {
    public static void main(String[] args) {
        try {
            throw new Exception ("throw!");
        }
        catch(Exception ex) {
            System.out.println("catch!");
            System.exit(0);
        }
        finally {
            System.out.println("finally!");
        }       
    }
}

It outputs:

catch!

The finally catch will only be executed if control is ever returned to the catch, which as we can see is never guaranteed; determining if you execute the finally is basically reduced to the Halting Problem.

In practice, the finally block will usually be executed. Not always.

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Peter Norvig's Java IAQ: Infrequently Answered Questions has a bit on this:

Q: The code in a finally clause will never fail to execute, right?

Well, hardly ever. But here's an example where the finally code will not execute, regardless of the value of the boolean choice:

try {
    if (choice) {
        while (true) ;
    } else {
        System.exit(1);
    }
} finally {
    code.to.cleanup();
}