AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  ";" after if statement??          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message JS Guest Posted: Sun May 29, 2005 6:00 pm    Post subject: ";" after if statement?? What does it mean when a ";" is inserted after an if statement? if (x == 2){ System.out.println("x = 2"); }; Back to top Andrew McDonagh Guest Posted: Sun May 29, 2005 6:16 pm    Post subject: Re: ";" after if statement?? JS wrote: Quote: What does it mean when a ";" is inserted after an if statement? if (x == 2){ System.out.println("x = 2"); }; nothing...whilst it is not illegal - it is useless. Back to top Roland Guest Posted: Sun May 29, 2005 6:27 pm    Post subject: Re: ";" after if statement?? On 29-5-2005 20:00, JS wrote: Quote: What does it mean when a ";" is inserted after an if statement? if (x == 2){ System.out.println("x = 2"); }; It's a so-called empty statement. It does nothing. However it can become unreachable (causing a compilation error), like in the following example: public static int abs(int i) { if (i<0) { return -i; } else { return i; } ; // unreachable } -- Regards, Roland de Ruiter ___ ___ /__/ w_/ /__/ / /_/ / Back to top JS Guest Posted: Sun May 29, 2005 7:13 pm    Post subject: Re: ";" after if statement?? "Roland" <roland (AT) phony (DOT) biz> skrev i en meddelelse news:429a097f$0$17211$e4fe514c (AT) news (DOT) xs4all.nl... Quote: On 29-5-2005 20:00, JS wrote: What does it mean when a ";" is inserted after an if statement? if (x == 2){ System.out.println("x = 2"); }; It's a so-called empty statement. It does nothing. Ok if I put a ";" after an if-statement that if statment will not be evaluated? Back to top Roland Guest Posted: Sun May 29, 2005 7:45 pm    Post subject: Re: ";" after if statement?? On 29-5-2005 21:13, JS wrote: Quote: "Roland" <roland (AT) phony (DOT) biz> skrev i en meddelelse news:429a097f$0$17211$e4fe514c (AT) news (DOT) xs4all.nl... On 29-5-2005 20:00, JS wrote: What does it mean when a ";" is inserted after an if statement? if (x == 2){ System.out.println("x = 2"); }; It's a so-called empty statement. It does nothing. Ok if I put a ";" after an if-statement that if statment will not be evaluated? No, the if statement of your example *will* be executed (that is: the test x==2, and depending on its outcome also the println). It's like if (x == 2){ System.out.println("x = 2"); }System.out.print("foo"); but without System.out.print("foo") And this is similar to if (x == 2){ System.out.println("x = 2"); } System.out.print("foo"); The <if> statement will be executed (the test and optionally the println), and also the statement <System.out.print("foo");> will executed. Likewise your example is similar to if (x == 2){ System.out.println("x = 2"); } ; The <if> statement will be executed (the test etc), and also the empty statement <;> will executed. But the empty statement does nothing, so nothing will change. So far the analogy. Because an empty statement doesn't do a thing, the Java compiler will not generate code for it (any smart Java compiler, that is; a "dumb" compiler might generate some no-op code for it). -- Regards, Roland de Ruiter ___ ___ /__/ w_/ /__/ / /_/ / Back to top Bjorn Abelli Guest Posted: Mon May 30, 2005 9:44 am    Post subject: Re: ";" after if statement?? "JS" wrote... Quote: "Roland" wrote... On 29-5-2005 20:00, JS wrote: What does it mean when a ";" is inserted after an if statement? if (x == 2){ System.out.println("x = 2"); }; It's a so-called empty statement. It does nothing. Ok if I put a ";" after an if-statement that if statment will not be evaluated? It will be evaluated, but notice the difference between the following constructions: ----------------------------------- if (x == 2) System.out.println("x = 2"); ----------------------------------- if (x == 2); System.out.println("x = 2"); ----------------------------------- They look very similar, don't they... ;-) A misplaced empty statement can make a logic error in the code which can be difficult to discover. In both cases the condition is evaluated, and hence the following statement is executed. But in the second example the following statement is the *empty* statement. The printout in the latter example will always execute, as it's not a part of the if-block. // Bjorn A Back to top Tor Iver Wilhelmsen Guest Posted: Mon May 30, 2005 2:49 pm    Post subject: Re: ";" after if statement?? "Bjorn Abelli" <bjorn_abelli (AT) DoNotSpam (DOT) hotmail.com> writes: Quote: A misplaced empty statement can make a logic error in the code which can be difficult to discover. Which IMHO is why Java should have required braces for if, while, do etc. like it does for try, catch, finally, synchronized. Back to top Fred L. Kleinschmidt Guest Posted: Tue May 31, 2005 3:39 pm    Post subject: Re: ";" after if statement?? JS wrote: Quote: "Roland" <roland (AT) phony (DOT) biz> skrev i en meddelelse news:429a097f$0$17211$e4fe514c (AT) news (DOT) xs4all.nl... On 29-5-2005 20:00, JS wrote: What does it mean when a ";" is inserted after an if statement? if (x == 2){ System.out.println("x = 2"); }; It's a so-called empty statement. It does nothing. Ok if I put a ";" after an if-statement that if statment will not be evaluated? As others have said, that semicolon does nothing. The code fragment is the same as: if (x == 2){ System.out.println("x = 2"); } ; Note that the following is also legal: if (x == 2){ System.out.println("x = 2"); };;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; y = 5;;;;;;;; It just contains a whole bunch of useless empty statements. -- Fred L. Kleinschmidt Boeing Associate Technical Fellow Technical Architect, Common User Interface Services M/S 2R-94 (206)544-5225 Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AppletTalk.com Forum Index -> Java Help All times are GMT Page 1 of 1   Jump to: Select a forum Java Newsgroups----------------Java DiscussionsWeb-based java games comp.lang.java 3D Graphics API's for Java Java: Support and criticism Java System Announcements comp.lang.java.api JavaBeans Java and CORBA Java and Databases comp.lang.java.developer Java GUI Toolkits Java Help comp.lang.java.javascript JVM, native methods and hardware comp.lang.java.misc Java Language Programming Security and Java comp.lang.java.setup Java Software Tools comp.lang.java.tech ibm.software.java.linux  Non-English Java Newsgroups----------------Java Language (German)Language Java (Français)Java (Italian)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.