AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Why so many imports instead of java.io.* ? Goto page 1, 2  Next          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message Timothy Madden Guest Posted: Tue Aug 14, 2012 10:23 am    Post subject: Why so many imports instead of java.io.* ? Hello Is it just me or people tend to enumerate all the needed classes for a Java source file each in its own import line ? Why is it better to use: import java.io.IOException import java.io.FileNotFoundException import java.io.FileOutputStream import ... instead of just: import java.io.* ? Which, by the way, also needs no maintenance in case a new class or exception is needed in the file at a later time. Thank you, Timothy Madden Back to top Eric Sosman Guest Posted: Tue Aug 14, 2012 10:45 am    Post subject: Re: Why so many imports instead of java.io.* ? On 8/14/2012 8:23 AM, Timothy Madden wrote: Quote: Hello Is it just me or people tend to enumerate all the needed classes for a Java source file each in its own import line ? Why is it better to use: import java.io.IOException import java.io.FileNotFoundException import java.io.FileOutputStream import ... instead of just: import java.io.* ? Which, by the way, also needs no maintenance in case a new class or exception is needed in the file at a later time. On the other hand, it *will* need maintenance if the next Java release adds a java.io.Wotsit class, and your file already has its own Wotsit. Import them one by one and the new Wotsit won't clash with yours; import them en masse and it will. The rest of the answer, I think, is that Somebody Somewhere decided that it was "better style" to import individually than by wildcard, and SS' opinion got codified into the out-of-the-box settings for tools like Eclipse and NetBeans. Bowing to SS' ideas, these tools complain about wildcard imports, while at the same time making it easy to generate the individual imports. Most people don't tinker much with the out-of-the-box settings, so the code they create with these IDE's follow that style. -- Eric Sosman esosman@ieee-dot-org.invalid Back to top Jeff Higgins Guest Posted: Tue Aug 14, 2012 11:05 am    Post subject: Re: Why so many imports instead of java.io.* ? On 08/14/2012 08:23 AM, Timothy Madden wrote: Quote: Hello Is it just me or people tend to enumerate all the needed classes for a Java source file each in its own import line ? I suspect it boils down to one of: "I want to.", I have to.", or "Huh?". Back to top Patricia Shanahan Guest Posted: Tue Aug 14, 2012 11:16 am    Post subject: Re: Why so many imports instead of java.io.* ? On 8/14/2012 5:45 AM, Eric Sosman wrote: Quote: On 8/14/2012 8:23 AM, Timothy Madden wrote: Hello Is it just me or people tend to enumerate all the needed classes for a Java source file each in its own import line ? Why is it better to use: import java.io.IOException import java.io.FileNotFoundException import java.io.FileOutputStream import ... instead of just: import java.io.* ? Which, by the way, also needs no maintenance in case a new class or exception is needed in the file at a later time. On the other hand, it *will* need maintenance if the next Java release adds a java.io.Wotsit class, and your file already has its own Wotsit. Import them one by one and the new Wotsit won't clash with yours; import them en masse and it will. The rest of the answer, I think, is that Somebody Somewhere decided that it was "better style" to import individually than by wildcard, and SS' opinion got codified into the out-of-the-box settings for tools like Eclipse and NetBeans. Bowing to SS' ideas, these tools complain about wildcard imports, while at the same time making it easy to generate the individual imports. Most people don't tinker much with the out-of-the-box settings, so the code they create with these IDE's follow that style. I don't think the out-of-box settings in e.g. Eclipse should drive actual programming style. A programmer who prefers wildcard imports should use them, and tell the IDE not to warn on it. I would perhaps be too lazy to do single class imports without IDE support. Personally, I prefer specific class imports because that way the imports give a quick overview of the external features the class uses. Patricia Back to top Eric Sosman Guest Posted: Tue Aug 14, 2012 12:52 pm    Post subject: Re: Why so many imports instead of java.io.* ? On 8/14/2012 9:16 AM, Patricia Shanahan wrote: Quote: On 8/14/2012 5:45 AM, Eric Sosman wrote: On 8/14/2012 8:23 AM, Timothy Madden wrote: Hello Is it just me or people tend to enumerate all the needed classes for a Java source file each in its own import line ? Why is it better to use: import java.io.IOException import java.io.FileNotFoundException import java.io.FileOutputStream import ... instead of just: import java.io.* ? Which, by the way, also needs no maintenance in case a new class or exception is needed in the file at a later time. On the other hand, it *will* need maintenance if the next Java release adds a java.io.Wotsit class, and your file already has its own Wotsit. Import them one by one and the new Wotsit won't clash with yours; import them en masse and it will. The rest of the answer, I think, is that Somebody Somewhere decided that it was "better style" to import individually than by wildcard, and SS' opinion got codified into the out-of-the-box settings for tools like Eclipse and NetBeans. Bowing to SS' ideas, these tools complain about wildcard imports, while at the same time making it easy to generate the individual imports. Most people don't tinker much with the out-of-the-box settings, so the code they create with these IDE's follow that style. I don't think the out-of-box settings in e.g. Eclipse should drive actual programming style. A programmer who prefers wildcard imports should use them, and tell the IDE not to warn on it. Whether they "should" or not, I rather think they tend to. You've got this IDE with about a jillion configurable behaviors, and you only tweak those that are actual pain points. If you prefer wildcard imports strongly enough to spend the time finding the proper knob you'll do so -- but if it doesn't bother you that much you won't, and the default will win. Case in point: Me, the exemplar of lazy programmers. Some years ago NetBeans would use wildcards if you imported N or more classes from the same package, individual imports for fewer. At the time, I spent the small effort to find where N was configured, and adjusted the threshold a little. But in recent NetBeans versions that configuration has either vanished or moved somewhere else, and guess what? I haven't spent the time to try to find it, but have simply gone with the flow and let NetBeans manage the imports as it chooses. It means that in some of my .java files you need to scroll a fair way down before you find anything interesting, which is a little irritating -- but not irritating enough to get me to try to do something about it. (An ironic oddity: In NetBeans, if you refactor a class by moving it from oldpackage to newpackage, NB adds `import oldpackage.*;' so any oldpackage classes -- that used to be imported automatically under the "same package" rule -- are still available in newpackage. Then when you edit the refactored file, NB complains about the wildcard import ...) Quote: I would perhaps be too lazy to do single class imports without IDE support. For me, you can delete the "perhaps." Lacking IDE help, I'd use wildcard imports all over the place to duck the effort of staying up-to-date with every single class. And I might get unlucky when the java.io.Wotsit class appears next year ... Quote: Personally, I prefer specific class imports because that way the imports give a quick overview of the external features the class uses. When it's a shortish list, yes. When you're writing Swing code, you may find that the import list is so long as to be obfuscatory rather than explanatory. -- Eric Sosman esosman@ieee-dot-org.invalid Back to top Roedy Green Guest Posted: Tue Aug 14, 2012 10:46 pm    Post subject: Re: Why so many imports instead of java.io.* ? On Tue, 14 Aug 2012 15:23:02 +0300, Timothy Madden <terminatorul (AT) gmail (DOT) com> wrote, quoted or indirectly quoted someone who said : Quote: Which, by the way, also needs no maintenance in case a new class or exception is needed in the file at a later time. My IDE, IntelliJ lets me configure how many classes it should take to collapse to *. It pretty well handles inserting them automatically. It is nice to have the list spelled out. You can tell quite a bit about what a class does just by looking at the import list. * can get you in trouble e.g. List which has two completely different meanings. -- Roedy Green Canadian Mind Products http://mindprod.com A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it. ~ Max Planck 1858-04-23 1947-10-04 Back to top Lew Guest Posted: Tue Aug 14, 2012 11:31 pm    Post subject: Re: Why so many imports instead of java.io.* ? Timothy Madden wrote: Quote: Is it just me or people tend to enumerate all the needed classes for a Java source file each in its own import line ? There is a strong indication that import-on-demand is not as good a practice as single-type imports. <http://javadude.com/articles/importondemandisevil.html> <http://www.javabestpractice.com/java/disadvantage-of-using-wildcards-in-java-import-statements.html> "Using single-type imports is quite useful and an absolute requirement in the open source community as this code is usually really reviewed. Using single-type imports makes it easy for the code reader to quickly find out the package a particular type is in: You just search for the type name from the start of the source file." <http://jalopy.sourceforge.net/existing/imports.html> For arguments on both sides: <http://stackoverflow.com/questions/147454/why-is-using-a-wild-card-with-a-java-import-statement-bad> And in general, why not do a search yourself across the InterWebz? <http://lmgtfy.com/?q=java+import+on+demand+vs.+single-type+import> Quote: Why is it better to use: import java.io.IOException import java.io.FileNotFoundException import java.io.FileOutputStream import ... instead of just: import java.io.* ? Less confusion, elimination of simple-name collisions, more explicit documentation of what types it uses. Quote: Which, by the way, also needs no maintenance in case a new class or exception is needed in the file at a later time. Not true. It will need maintenance if that type name conflicts with another. You don't actually need any import directives in a program at all. The maintenance required for single-type import is negligible and not worth avoiding. -- Lew Back to top Timothy Madden Guest Posted: Thu Aug 16, 2012 11:39 am    Post subject: Re: Why so many imports instead of java.io.* ? On 08/15/2012 02:31 AM, Lew wrote: Quote: Timothy Madden wrote: Is it just me or people tend to enumerate all the needed classes for a Java source file each in its own import line ? There is a strong indication that import-on-demand is not as good a practice as single-type imports. http://javadude.com/articles/importondemandisevil.html http://www.javabestpractice.com/java/disadvantage-of-using-wildcards-in-java-import-statements.html "Using single-type imports is quite useful and an absolute requirement in the open source community as this code is usually really reviewed. Using single-type imports makes it easy for the code reader to quickly find out the package a particular type is in: You just search for the type name from the start of the source file." http://jalopy.sourceforge.net/existing/imports.html For arguments on both sides: http://stackoverflow.com/questions/147454/why-is-using-a-wild-card-with-a-java-import-statement-bad And in general, why not do a search yourself across the InterWebz? http://lmgtfy.com/?q=java+import+on+demand+vs.+single-type+import Why is it better to use: import java.io.IOException import java.io.FileNotFoundException import java.io.FileOutputStream import ... instead of just: import java.io.* ? Less confusion, elimination of simple-name collisions, more explicit documentation of what types it uses. Which, by the way, also needs no maintenance in case a new class or exception is needed in the file at a later time. Not true. It will need maintenance if that type name conflicts with another. You don't actually need any import directives in a program at all. The maintenance required for single-type import is negligible and not worth avoiding. Thank you, After reading the links (one of wich is currently broken) I see that import lists are a work-around for a language-design problem... Though I still find import-list a problem for /all/ Java-language programmers in the world (which is only made a little easier by proper IDEs), I agree with the them now. They should be used for future compatibility between your code and the Java run-time classes. I guess this issue has been a minus for Sun/Oracle since JDK 1.2 onwards. Timothy Madden Back to top Eric Sosman Guest Posted: Thu Aug 16, 2012 1:51 pm    Post subject: Re: Why so many imports instead of java.io.* ? On 8/16/2012 9:39 AM, Timothy Madden wrote: Quote: [...] After reading the links (one of wich is currently broken) I see that import lists are a work-around for a language-design problem... Not sure what "problem" you think they work around. The import directive is a convenience, nothing more: It allows you to abbreviate java.io.BufferedReader as just BufferedReader, but that's all. Off-hand, I can't think of a language that has namespaces or namespace-like things that doesn't also have some way to allow abbreviations of this kind. If there is such a language, I bet it's verbose. Remember the Monty Python skit in which an announcer speaks of the composer Johann Gambolputty de von Ausfern- schplenden- schlitter- crasscrenbon- fried- digger- dingle- dangle- dongle- dungle- burstein- von- knacker- thrasher- apple- banger- horowitz- ticolensic- grander- knotty- spelltinkle- grandlich- grumblemeyer- spelterwasser- kurstlich- himbleeisen- bahnwagen- gutenabend- bitte- ein- nürnburger- bratwustle- gerspurten- mitz- weimache- luber- hundsfut- gumberaber- shönedanker- kalbsfleisch- mittler- aucher von Hautkopft of Ulm .... and recites the entire thing at every mention? Hey, Java could have been like that! -- Eric Sosman esosman@ieee-dot-org.invalid Back to top Timothy Madden Guest Posted: Fri Aug 17, 2012 10:08 am    Post subject: Re: Why so many imports instead of java.io.* ? On 08/16/2012 06:51 PM, Eric Sosman wrote: Quote: On 8/16/2012 9:39 AM, Timothy Madden wrote: [...] After reading the links (one of wich is currently broken) I see that import lists are a work-around for a language-design problem... Not sure what "problem" you think they work around. The import directive is a convenience, nothing more: It allows you to abbreviate java.io.BufferedReader as just BufferedReader, but that's all. Off-hand, I can't think of a language that has namespaces or namespace-like things that doesn't also have some way to allow abbreviations of this kind. If there is such a language, I bet it's verbose. I see what you mean. A simple test shows that the same problem exists with C++ namespaces and its using directive. FreePascal documentation also says that a duplicate identifier is imported from the unit last specified in the uses clause. I think this approach produces the same problem as the open imports from Java (or C++), and even worse ones. Python is a little smarter: even after import, you still have to use the qualified name. Or you can import the qualified name explicitly, than you can use the simple name. I also tried perl, but I am not good with it. Perl modules look like they need explicit exports inside the module, if the import directive is to import anything other than the module name. And these explicit exports are scarce. All other module symbols need to be accessed as qualified names, like in python, so it's still good. I believe Ruby also exhibits no such "import of an open namespace" problem. At least not directly, because in Ruby a module can serve as a base class for a derived one, which is also a form of importing (and extending) an existing namespace. But that is a different problem, related to OOP, and which does not produce conflicts the same way imports do. So I see some languages have this problem when trying to import an "open namespace", while other languages do not allow the "open namespace" to be imported directly. Maybe what Java needs is some new syntax like: import com.oracle.multiprocessing.* into mp; and than any function f() from com.oracle.multiprocessing can only be refferred to as mp.f(); P.S. Python wins (and it rocks, too) ! Thank you, Timothy Madden Back to top Gene Wirchenko Guest Posted: Fri Aug 17, 2012 5:53 pm    Post subject: Re: Why so many imports instead of java.io.* ? On Fri, 17 Aug 2012 11:26:14 -0700 (PDT), Lew <lewbloch (AT) gmail (DOT) com> wrote: Quote: Timothy Madden wrote: P.S. Python wins (and it rocks, too) ! Language War! It's futile to do Language War with Java partisans because we agree with the criticisms of the language, and respond with, "Y'think *that's* bad? What about <insert favorite Java feature to deprecate here>?" It's what keeps Java vibrant - its community complains more about it than its opposition, and its fanboys engage in the opposite of the sort of religiously fervent proselytizing that distinguishes the fanboys of other computer languages. But you save it for the formatting and variable naming conventions. Sincerely, Gene Wirchenko Back to top Lew Guest Posted: Fri Aug 17, 2012 6:26 pm    Post subject: Re: Why so many imports instead of java.io.* ? Timothy Madden wrote: Quote: P.S. Python wins (and it rocks, too) ! Language War! It's futile to do Language War with Java partisans because we agree with the criticisms of the language, and respond with, "Y'think *that's* bad? What about <insert favorite Java feature to deprecate here>?" It's what keeps Java vibrant - its community complains more about it than its opposition, and its fanboys engage in the opposite of the sort of religiously fervent proselytizing that distinguishes the fanboys of other computer languages. -- Lew Back to top Gene Wirchenko Guest Posted: Fri Aug 17, 2012 6:27 pm    Post subject: Re: Why so many imports instead of java.io.* ? On Fri, 17 Aug 2012 12:58:18 -0700 (PDT), Lew <lewbloch (AT) gmail (DOT) com> wrote: Quote: Gene Wirchenko wrote: Lew wrote: Timothy Madden wrote: P.S. Python wins (and it rocks, too) ! Language War! It's futile to do Language War with Java partisans because we agree with the criticisms of the language, and respond with, "Y'think *that's* bad? What about <insert favorite Java feature to deprecate here>?" It's what keeps Java vibrant - its community complains more about it than its opposition, and its fanboys engage in the opposite of the sort of religiously fervent proselytizing that distinguishes the fanboys of other computer languages. But you save it for the formatting and variable naming conventions. I don't understand your remark. I can't recall having complained against the Java code conventions. What are you attempting to communicate there, Gene? Lew, that is rather disingenuous of you. Whenever anyone uses a different convention, they get put down and rather harshly. It is quite fanatic what is done. Sincerely, Gene Wirchenko Back to top Patricia Shanahan Guest Posted: Fri Aug 17, 2012 7:39 pm    Post subject: Re: Why so many imports instead of java.io.* ? On 8/17/2012 12:58 PM, Lew wrote: Quote: Gene Wirchenko wrote: Lew wrote: Timothy Madden wrote: P.S. Python wins (and it rocks, too) ! Language War! It's futile to do Language War with Java partisans because we agree with the criticisms of the language, and respond with, "Y'think *that's* bad? What about <insert favorite Java feature to deprecate here>?" It's what keeps Java vibrant - its community complains more about it than its opposition, and its fanboys engage in the opposite of the sort of religiously fervent proselytizing that distinguishes the fanboys of other computer languages. But you save it for the formatting and variable naming conventions. I don't understand your remark. I can't recall having complained against the Java code conventions. What are you attempting to communicate there, Gene? Your attempts to encourage universal use of one set of Java coding conventions are sometimes difficult to distinguish from religiously fervent proselytizing. Patricia Back to top Lew Guest Posted: Fri Aug 17, 2012 7:58 pm    Post subject: Re: Why so many imports instead of java.io.* ? Gene Wirchenko wrote: Quote: Lew wrote: Timothy Madden wrote: P.S. Python wins (and it rocks, too) ! Language War! It's futile to do Language War with Java partisans because we agree with the criticisms of the language, and respond with, "Y'think *that's* bad? What about <insert favorite Java feature to deprecate here>?" It's what keeps Java vibrant - its community complains more about it than its opposition, and its fanboys engage in the opposite of the sort of religiously fervent proselytizing that distinguishes the fanboys of other computer languages. But you save it for the formatting and variable naming conventions. I don't understand your remark. I can't recall having complained against the Java code conventions. What are you attempting to communicate there, Gene? -- Lew 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 Goto page 1, 2  Next Page 1 of 2   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.