Re: Is there a better way to throw this exception?

[Peter Levart]

On 06/06/2013 11:42 AM, Weijun Wang wrote:
Hi All
I have a method that could throw two kinds of checked exceptions and 
possibly other unchecked ones:

   void once() throws One, Two

Now I have a wrapper method that calls once() for multiple times, and 
want to throw the first exception if *all* fails. Now it looks like

   void multiple() throws One, Two {
      Exception saved = null;
      for (all chances) {
         try {
            once();
            return;
         } catch (Exception e) {
            if (saved != null) saved = e;
         }
      }
      if (saved instanceof One) {
         throw (One)saved;
      } else if (saved instanceof One) {
         throw (Two)saved;
      } else if (saved instanceof RuntimeException) {
         throw (RuntimeException)saved;
      } else {
         // Not likely, but I've already wrote so many lines.
         throw new RuntimeException(saved);
      }
   }

Is there any way I can make it shorter?

Hi Max,

If you don't mind re-throwing the last exception thrown instead of the 
first and you can transform your for loop into a while loop, for example:

    void multiple() throws One, Two {
        int tries = 10;
        int i = 0;
        while (true) {
            try {
                once();
                return;
            } catch (Exception e) {
                if (++i >= tries) {
                    throw e;
                }
            }
        }
    }


...otherwise you can re-throw the first exception if you can extract the 
first loop iteration out of the loop:


    void multiple() throws One, Two {
        try {
            once(); // first chance
            return;
        } catch (Exception e) {
            for (rest of chances) {
                try {
                    once();
                    return;
                }
                catch (Exception ignore) {}
            }
            throw e;
        }
    }


Regards, Peter


Thanks
Max