AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  newbie help interpreting this code from book          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message James Bond Guest Posted: Sat Aug 14, 2004 11:00 pm    Post subject: newbie help interpreting this code from book I have been reading Thinking in Java (2nd E., Bruce Eckel) and there is one little thing I simply cannot figure out about this one code snippet in the book. Here it is: public class IfElse2 { static int test(int testval, int target) { int result = 0; if(testval > target) return +1; else if(testval < target) return -1; else return 0; // Match } public static void main(String[] args) { System.out.println(test(10, 5)); System.out.println(test(5, 10)); System.out.println(test(5, 5)); } } My question is why is the variable 'result' defined and given a value in line 3? Since the method returns a literal in every case, I am confused as to why to author is doing this. TIA for any help. James Back to top Paul Lutus Guest Posted: Sat Aug 14, 2004 11:09 pm    Post subject: Re: newbie help interpreting this code from book James Bond wrote: Quote: I have been reading Thinking in Java (2nd E., Bruce Eckel) and there is one little thing I simply cannot figure out about this one code snippet in the book. Here it is: public class IfElse2 { static int test(int testval, int target) { int result = 0; if(testval > target) return +1; else if(testval < target) return -1; else return 0; // Match } public static void main(String[] args) { System.out.println(test(10, 5)); System.out.println(test(5, 10)); System.out.println(test(5, 5)); } } My question is why is the variable 'result' defined and given a value in line 3? Since the method returns a literal in every case, I am confused as to why to author is doing this. It seems the author made a mistake. He apparently intended to use the "result" variable, but then forgot all about it. This is how the method was probably meant to look: static int test(int testval, int target) { int result = 0; if(testval > target) result = 1; else if(testval < target) result = -1; return result; } Here is another variation on the basic idea, but not one suitable for a beginning textbook: static int test(int testval, int target) { return (testval < target)?-1:(testval > target)?1:0; } The bottom line is, even textbooks aren't perfect. Maybe this was the author's tricky way to get you to think about the code and not assume that it is beyond reproach. And maybe it was a simple mistake. -- Paul Lutus http://www.arachnoid.com Back to top thufir.hawat@mail.com Guest Posted: Sat Aug 14, 2004 11:13 pm    Post subject: Re: newbie help interpreting this code from book On Sat, 14 Aug 2004, James Bond wrote: [..] Quote: int result = 0; [..] My question is why is the variable 'result' defined and given a value in line 3? Since the method returns a literal in every case, I am confused as to why to author is doing this. [..] unless result were final, which it isn't, it's just good form. in java some primitives are automatically initialised, such as to zero, while others might have a garbage value without initialization. I think primitives within methods might have garbage values unless initialized. There's still the unanswered question of why it's good form, of course ;) Thufir Hawat Back to top Tor Iver Wilhelmsen Guest Posted: Sun Aug 15, 2004 7:42 am    Post subject: Re: newbie help interpreting this code from book [email]thufir.hawat (AT) mail (DOT) com[/email] writes: Quote: unless result were final, which it isn't, it's just good form. in java some primitives are automatically initialised, such as to zero, while others might have a garbage value without initialization. I think the real question was that "result" is defined ad initialized, but never *used* for anything after that. Back to top James Bond Guest Posted: Sun Aug 15, 2004 7:52 am    Post subject: Re: newbie help interpreting this code from book Paul Lutus <nospam (AT) nosite (DOT) zzz> wrote in news:10ht6su39f0j22 (AT) corp (DOT) supernews.com: Quote: James Bond wrote: I have been reading Thinking in Java (2nd E., Bruce Eckel) and there is one little thing I simply cannot figure out about this one code snippet in the book. Here it is: public class IfElse2 { static int test(int testval, int target) { int result = 0; if(testval > target) return +1; else if(testval < target) return -1; else return 0; // Match } public static void main(String[] args) { System.out.println(test(10, 5)); System.out.println(test(5, 10)); System.out.println(test(5, 5)); } } My question is why is the variable 'result' defined and given a value in line 3? Since the method returns a literal in every case, I am confused as to why to author is doing this. It seems the author made a mistake. He apparently intended to use the "result" variable, but then forgot all about it. This is how the method was probably meant to look: static int test(int testval, int target) { int result = 0; if(testval > target) result = 1; else if(testval < target) result = -1; return result; } Here is another variation on the basic idea, but not one suitable for a beginning textbook: static int test(int testval, int target) { return (testval < target)?-1:(testval > target)?1:0; } The bottom line is, even textbooks aren't perfect. Maybe this was the author's tricky way to get you to think about the code and not assume that it is beyond reproach. And maybe it was a simple mistake. Okay, thank you. I suspected that it was just an error, but being such a newbie I knew there could just as easily be something else I was missing. I appreciate your (and the other poster's) time in helping me with this. James Back to top thufir.hawat@mail.com Guest Posted: Sun Aug 15, 2004 9:15 am    Post subject: Re: newbie help interpreting this code from book On Sun, 15 Aug 2004, Tor Iver Wilhelmsen wrote: Quote: thufir.hawat (AT) mail (DOT) com writes: unless result were final, which it isn't, it's just good form. in java some primitives are automatically initialised, such as to zero, while others might have a garbage value without initialization. I think the real question was that "result" is defined ad initialized, but never *used* for anything after that. doh! Thufir Hawat Back to top Chris Smith Guest Posted: Wed Aug 18, 2004 2:53 pm    Post subject: Re: newbie help interpreting this code from book [email]thufir.hawat (AT) mail (DOT) com[/email] wrote: Quote: unless result were final, which it isn't, it's just good form. in java some primitives are automatically initialised, such as to zero, while others might have a garbage value without initialization. I think primitives within methods might have garbage values unless initialized. I hate to be critical, but this is dead wrong and very misleading. If you were talking about C or C++, then you'd be right that uninitialized local variables may have arbitrary values and should not be used. However, the picture in Java is much different. In Java, an uninitialized local variable can never be accessed. Before you can write (and successfully compile) any expression that reads the value of a local variable, the compiler has to be able to prove to itself that the variable has been successfully initialized. This changes everything; whereas it's good form in C and C++ to initialize a variable as it's declared, it is bad form in Java -- unless of course the algorithm itself asks for that variable to have that value at that time. By senselessly initializing variables, you are lying to the compiler and avoiding some of the help it could provide you by complaining about an uninitialized variable. After all, a senseless initialization that's added out of habit is almost as little use as an undefined value. Unfortunately, the instinctive initialization of locals is carried over from C and C++ programmers, and propogated by Java programmers who imagine themselves in a duel against the compiler and refuse to make use of its help, which is freely offered. -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation Back to top Tony Morris Guest Posted: Fri Aug 27, 2004 4:40 am    Post subject: Re: newbie help interpreting this code from book All fields will have a default value during initialisation (even if they have an explicit assignment). All locals (variables that aren't fields) will not have a value, and it will be a compile-time error to use them if they don't have "definite assignment" (to quote the title of the chapter from the JLS). A variable will never hold a "garbage value". -- Tony Morris http://xdweb.net/~dibblego/ 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.