Re: do loop bug?

From:
"Mike Schilling" <mscottschilling@hotmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 10 Aug 2006 05:32:00 GMT
Message-ID:
<kxzCg.9675$gY6.7041@newssvr11.news.prodigy.com>
"Patricia Shanahan" <pats@acm.org> wrote in message
news:65wCg.6665$0e5.801@newsread4.news.pas.earthlink.net...

emrefan wrote:

Does this program below indicate to you that there's a bug in java's do
loop. Or is it just one of those many traps that I've fallen into and
I've only got myself to blame? I was expecting the two loops would
behave much the same. Have I been bitten by the optimizer?

public class DoLoopBug {
   public static void main( String[] args ) {
      int retryCnt = 0;
      doLoop1: do {
         try {
            if (retryCnt < 3)
               throw new java.net.ConnectException();
            break;
         }
         catch (Exception e) {
            System.out.println( "caught exception; retryCnt=" +
retryCnt );
            if (++retryCnt < 20)
               continue doLoop1;
         }
      } while (false);

      System.out.println( "after doLoop1, retryCnt = " + retryCnt +
"\n" );

      retryCnt = 0;

      doLoop2: do {
         try {
            if (retryCnt < 3)
               throw new java.net.ConnectException();
            break;
         }
         catch (Exception e) {
            System.out.println( "caught exception; retryCnt=" +
retryCnt );
            if (++retryCnt < 20)
               continue doLoop2;
         }
      } while (true); // Here's difference from DoLoop1

      System.out.println( "after doLoop2, retryCnt = " + retryCnt );
   }
}


The results I get are:

caught exception; retryCnt=0
after doLoop1, retryCnt = 1

caught exception; retryCnt=0
caught exception; retryCnt=1
caught exception; retryCnt=2
after doLoop2, retryCnt = 3

which is what I expected.

Each continue effectively jumps to its loop's while expression
evaluation.


And both "continue"s are unnecessary, since evaluating the "while" is the
next thing to be done anyway, making mw wonder what the intention of the
code is.

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