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Groups > comp.lang.java.programmer > #11214

Re: Curious compiler warning

From Novice <novice@example..com>
Newsgroups comp.lang.java.programmer
Subject Re: Curious compiler warning
Date 2012-01-11 04:55 +0000
Organization Your Company
Message-ID <Xns9FD6F359B6B60jpnasty@94.75.214.39> (permalink)
References <Xns9FD6D451D5F1Djpnasty@94.75.214.39> <jeir2s$7v0$3@news.albasani.net>

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Lew <noone@lewscanon.com> wrote in news:jeir2s$7v0$3@news.albasani.net:

> On 01/10/2012 05:51 PM, Novice wrote:
>> I'm getting an odd compiler warning that I don't really understand. I
>> wonder if anyone can enlighten me on the meaning of this message.
>> Basically, I'm not sure what the compiler's problem is with what I'm
>> doing or the best way to make it happy.
>>
>> I've got a fairly simply method name foo() that takes two parameters,
>> ints called start and finish. During this method, I decrement start
>> and finish and then calls another method, bar(), passing the
>> decremented versions of start and finish. For some reason, the
>> compiler objects to the statements where I decrement start and finish
>> and says "the parameter should not be assigned". I'm running Eclipse
>> 3.7.1 with a 1.6.18 JDK. 
>>
>> So here's what the code looks like:
>>
>> public static int foo(int start, int finish) {
>>
>> /* Other stuff */
>>
>>    start--;
>>    finish--;
>>
>>    bar(start, finish);
>> }
>>
>> It's the start--; and finish--; lines that are raising the warnings.
>>
>> What exactly is wrong with doing that? And what is the best way to
>> make the compiler happy about that code?
> 
> What's exactly wrong is that the assignment to the parameters is
> thrown away, and does you no good.
> 
How so? My original code says - in my opinion - "thank you very much for 
the value but we need to adjust it a little by subtracting one, aside 
from that, it's perfect". It's not like we're changing start to an 
arbitrary value like 0 or 5 billion regardless of the original value. The 
code in this class basically just does String functions to count the 
number of occurrences of a string in another string but I'm assuming that 
the user will consider the initial character of the string being searched 
as '1' while Java's methods are all 0-based. I'm just subtracting one to 
bring the user's view of the situation in line with Java's view.

I'm just wondering why the compiler is so offended by "start--".... 

>> I modified the code as follows to get rid of the warnings but is it
>> really necessary to create two local variables just to eliminate the
>> warnings? Or is there a better way?
>>
>> public static int foo(int start, int finish) {
>>
>> /* Other stuff */
>>
>>    int myStart = start;
>>    myStart--;
>>
>>    int myFinish = finish;
>>    myFinish--;
>>
>>    bar(myStart, myFinish);
>> }
> 
> Yes, there's a better way; that one is silly.
> 
> public static int foo(int start, int finish) {
> 
> /* Other stuff */
> 
>    bar(start - 1, finish - 1);
> }
> 

Yes, I definitely like that better. Strangely enough, writing 

bar(start--, finish--); 

gives me the same warning as before, presumably for the same reason. 

-- 
Novice

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Curious compiler warning Novice <novice@example..com> - 2012-01-11 01:51 +0000
  Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 18:10 -0800
    Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 02:36 +0000
      Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 19:03 -0800
        Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 07:50 +0000
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 23:57 -0800
        Re: Curious compiler warning Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-11 05:47 -0400
          Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 13:25 +0000
            Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 06:58 -0800
              Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 07:01 -0800
              Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-11 10:03 -0800
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 23:30 -0800
              Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:10 -0800
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 23:32 -0800
                Re: Curious compiler warning Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-01-12 01:44 -0600
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:42 -0800
                Re: Curious compiler warning Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-01-12 10:51 -0600
                Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-12 07:50 -0800
                Re: Curious compiler warning Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-01-12 10:54 -0600
                Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
                Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-12 11:51 -0800
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 20:58 -0800
        Re: Curious compiler warning "Gavino" <invalid@invalid.invalid> - 2012-01-11 20:05 +0100
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:47 -0800
        Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-21 12:13 -0800
    Re: Curious compiler warning Novice <novice@example..com> - 2012-01-11 04:55 +0000
      Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 21:46 -0800
      Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 07:55 +0000
      Re: Curious compiler warning Roedy Green <see_website@mindprod.com.invalid> - 2012-01-11 01:35 -0800
        Re: Curious compiler warning "Gavino" <invalid@invalid.invalid> - 2012-01-11 20:05 +0100
          Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:18 -0800
            Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:55 -0800
              Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-12 11:59 -0800
            Re: Curious compiler warning Martin Gregorie <martin@address-in-sig.invalid> - 2012-01-13 00:02 +0000
              Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-12 16:11 -0800
                Re: Curious compiler warning Martin Gregorie <martin@address-in-sig.invalid> - 2012-01-13 01:31 +0000
          Re: Curious compiler warning Roedy Green <see_website@mindprod.com.invalid> - 2012-01-11 18:26 -0800
            Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-11 19:01 -0800
              Re: Curious compiler warning Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-11 23:23 -0500
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:00 -0800
            Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:50 -0800
        Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:14 -0800
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:05 -0800
            Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-12 12:02 -0800
  Re: Curious compiler warning Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-10 21:11 -0500
    Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 18:17 -0800
    Re: Curious compiler warning bugbear <bugbear@trim_papermule.co.uk_trim> - 2012-01-11 16:10 +0000
    Re: Curious compiler warning Lars Enderin <lars.enderin@telia.com> - 2012-01-11 20:45 +0100
      Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:09 -0800
      Re: Curious compiler warning Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2012-01-12 18:14 +0200
      Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
      Re: Curious compiler warning David Lamb <dalamb@cs.queensu.ca> - 2012-01-21 09:12 -0500
    Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:21 -0800
    Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:08 -0800
  Re: Eclipse 3.7.1 compiler warning v_borchert@despammed.com (Volker Borchert) - 2012-01-11 21:10 +0000

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