Try catch finally execution flow

If an exception is thrown in catch block of try-catch, then will the开发者_开发技巧 finally block be called?

    try
{
//some thing which throws error
}
catch
{
//again some thing throws error
}
finally
{
//final clean up
}

Here, will finally be called?

Thanks, Ashwani

In at least Java and C#, the finally block is always executed regardless how the try block exits.

If the answer were false, the finally construct would provide no advantage over simply including the code at the end of the try block.

Even though there's an exception or not in the try block, finally block is bound to execute. That's the way finally was designed.

If there's an exception in the try block, then control will be transferred to the catch block to match the generated exception and will then switch over the control to the finally block.

But in this case, if there isn't any exception generated in the try block, the control won't be transferred to the catch block because there wasn't any exception to catch.
But as I said earlier, the finally block is again bound to execute.

So, finally, the finally block will always be executed

The answer is yes. But what happens after the Finally block? To illustrate the full flow semantics, consider the following:

private int TryCatchFinallyFlow()
{
    int i, j = 0; // set j to non-zero

    try
    {
        i = 1 / j;
        goto lSkip; // comment out;

        return i; // comment out

      lSkip:;
    }
    catch (Exception)
    {
        i = 2;

        throw; // comment out
    }
    finally
    {
        i = 3;
    }

    i = 4;

    return i;
}

private void button1_Click(object sender, EventArgs e)
{
    int i;

    try
    {
        i = TryCatchFinallyFlow();
    }
    catch (Exception)
    {
        i = -1;
    }

    MessageBox.Show(i.ToString());
}

}

You can experiment with j being 0 or not zero, and with commenting out the three "comment out" lines. Step through in debug mode.

This will show you fully how the flows work.

In every language I know: Yes.

No if there is an exception in both the try and catch blocks as in your example above, control does not pass to the finally block. Illustration:

try
{
    //exception -> control goes to catch block.
}
catch
{
    //again exception ->  exits showing error
}
finally
{
    //control does not reach here
}

NOTE: If however this above code is wrapped inside some function and there is proper exception handling i.e. try... catch block in the calling function, then finally block does get executed and control moves from catch above to the calling function's catch. Illustration:

try
{
    //exception -> goes to catch block.
}
catch
{
    //again exception ->  goes to finally block
}
finally
{
    //code here is executed -> goes to calling function's catch block
}

Yes, finally block will be executed if there is an exception in catch block also.

This is the code of testing with debugging statements.

Code

public class Demo{
    public static void main(String args[]){
        int i,j,ans;


        try{
            System.out.println("Debug statement 1");
            i = 9;
            ans = i / 0;
            System.out.println("Debug statement 2");
        }
        catch(Exception e){
            System.out.println("Debug statement 3");
            j=5;
            ans = j/0;
            System.out.println("Debug statement 4");
        }
        finally{
            System.out.println("Finally Executed");
        }
    }
}

Output

Debug statement 1
Debug statement 3
Finally Executed
Exception in thread "main" java.lang.ArithmeticException: / by zero
        at Demo.main(Demo.java:15)