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Java Forum / General / November 2007void method()
Is a plain "void method()" public, protected or private by default? > Is a plain "void method()" public, protected or private by default? No. Unfortunately, Sun chose not to allow use of a keyword for the fourth access mode, "default access", which is really package access. http://java.sun.com/docs/books/jls/second_edition/html/names.doc.html#36154 Patricia > > Is a plain "void method()" public, protected or private by default? > > No. Unfortunately, Sun chose not to allow use of a keyword for the > fourth access mode, "default access", which is really package access. http://java.sun.com/docs/books/jls/second_edition/html/names.doc.html#36154 > Patricia so it's basically private? >>>Is a plain "void method()" public, protected or private by default? >> [quoted text clipped - 6 lines] > > so it's basically private? No, it is 'none of the above'. It means 'accessible to all classes within the same package'. As it says in the post you quoted and the link cited therein. > >>>Is a plain "void method()" public, protected or private by default? > >> > >>No. Unfortunately, Sun chose not to allow use of a keyword for the > >>fourth access mode, "default access", which is really package access. http://java.sun.com/docs/books/jls/second_edition/html/names.doc.html#36154 > >>Patricia > > [quoted text clipped - 3 lines] > within the same package'. As it says in the post you quoted and the link > cited therein. So what's this ThreadGroup method available to?: /** * Adds the specified Thread to this group. * @param t the Thread to be added * @exception IllegalThreadStateException If the Thread group has been destroyed. */ void add(Thread t) { synchronized (this) { if (destroyed) { throw new IllegalThreadStateException(); } if (threads == null) { threads = new Thread[4]; } else if (nthreads == threads.length) { Thread newthreads[] = new Thread[nthreads * 2]; System.arraycopy(threads, 0, newthreads, 0, nthreads); threads = newthreads; } threads[nthreads] = t; // This is done last so it doesn't matter in case the // thread is killed nthreads++; nUnstartedThreads--; } } >> No, it is 'none of the above'. It means 'accessible to all classes >> within the same package'. As it says in the post you quoted and the link >> cited therein. > > So what's this ThreadGroup method available to?: Do you read any of the answers you were receiving so far? The answer to the question is in the text you cited directly before asking. Again: >> It means 'accessible to all classes within the same package'. If you don't know what package ThreadGroup is in: If it's not specified explicitly as import-statement and you simply have a ThreadGroup in your code, it's java.lang. Regards, Lothar  SignatureLothar Kimmeringer E-Mail: spamfang@kimmeringer.de PGP-encrypted mails preferred (Key-ID: 0x8BC3CD81) Always remember: The answer is forty-two, there can only be wrong questions! >>> Is a plain "void method()" public, protected or private by default? >>> [quoted text clipped - 5 lines] > > so it's basically private? No, private is more restricted than default. A private method can only be accessed inside the body of the top level class that encloses its declaration. Patricia > A private method can only > be accessed inside the body of the top level class that encloses its > declaration. ... and its inner classes. Or is that what you mean with "inside the body"? Regards, Lothar SignatureLothar Kimmeringer E-Mail: spamfang@kimmeringer.de PGP-encrypted mails preferred (Key-ID: 0x8BC3CD81) Always remember: The answer is forty-two, there can only be wrong questions! On Wed, 7 Nov 2007 19:16:32 +0100, Lothar Kimmeringer <news200709@kimmeringer.de> wrote, quoted or indirectly quoted someone who said : >... and its inner classes. Or is that what you mean with "inside >the body"? they get complicated. See http://mindprod.com/jgloss/nestedclasses.html SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com >> A private method can only >> be accessed inside the body of the top level class that encloses its >> declaration. > > ... and its inner classes. Or is that what you mean with "inside > the body"? The exact statement in the JLS is: "Otherwise, if the member or constructor is declared private, then access is permitted if and only if it occurs within the body of the top level class (§7.6) that encloses the declaration of the member or constructor." I believe that is intended to include inner classes declarations. Patricia >so it's basically private? no. It is visible to all classes in the package. See http://mindprod.com/jgloss/scope.html Private is visible only to the current class. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com >so it's basically private? see http://mindprod.com/jgloss/gettingstarted.html You need at least one text book, perhaps out of date, and hence very cheap, to teach you the basics of the language syntax. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com > > > Is a plain "void method()" public, protected or private by default? > [quoted text clipped - 4 lines] > > so it's basically private? No; default ("package private", as mentioned elsewhere) access exists independently of private access. There's a useful progression of access levels: 'private' allows access from within the same top-level class. default allows access from anywhere private allows access, as well as to any other class in the same package. 'protected' allows access from anywhere default allows access, as well as from any subclass. 'public' allows access from anywhere protected allows access, as well as from anywhere else. (Ok, that one's a little contrived.) For the java.lang.ThreadGroup class, other classes in java.lang are allowed to manipulate its default-access members; since you can only add classes to this package via vendor-specific trickery (and you shouldn't do that), you can treat it as an implementation detail and pretend it doesn't exist. On the other hand, you can use default access in your own packages to allow closely-related classes (like a container and its iterator) to directly access one another's members, if that's the cleanest way to implement something. > Is a plain "void method()" public, protected or private by default? The default is called "package private", that is, it is only accessible within a package. Private allow only the one class to access, protected allow the class and it's subclasses access and last, public allow any class to access. Hope it was understandable =) > The default is called "package private", that is, it is only accessible > within a package. "package private". got it. cheers > Private allow only the one class to access, ... and its inner classes > protected allow the class > and it's subclasses access ... and include package visible as well. There is no protected as you know it e.g. with C++. > and last, public allow any class to access. At least that's correct ;-) Regards, Lothar SignatureLothar Kimmeringer E-Mail: spamfang@kimmeringer.de PGP-encrypted mails preferred (Key-ID: 0x8BC3CD81) Always remember: The answer is forty-two, there can only be wrong questions! So if a plain method (ie. void method()) is part of a class in the Sun JDK it's basically private? > So if a plain method (ie. void method()) is part of a class in the Sun JDK > it's basically private? There is no "basically private" access. There are four access levels, and a method or member's access is exactly one of the four, never "basically" any of them. If a method (as in your example) is declared without any access modifier, then it has exactly package-private access. Not private. Private access means accessible only to the class itself. Package-private is more exposed than that; in addition, any class in the same package has access to it. SignatureLew > > So if a plain method (ie. void method()) is part of a class in the Sun JDK > > it's basically private? [quoted text clipped - 10 lines] > -- > Lew I know but what I am saying is if you write a 3rd party app and create a new java.lang.ThreadGroup you can't use it's method "void add(Thread t)" >>> So if a plain method (ie. void method()) is part of a class in the Sun > JDK [quoted text clipped - 16 lines] > I know but what I am saying is if you write a 3rd party app and create a new > java.lang.ThreadGroup you can't use it's method "void add(Thread t)" void add(Thread t) is a method in ThreadGroup that has default (or package private) access. This mean that classes in java.lang can access this method (because it is package private) however as you are unable to 'add' classes to the java.lang package you can't access this method from your third party app. Actually in Eclipse you can write and compile a class in the java.lang package but if you try to run it you get java.lang.SecurityException: Prohibited package name: java.lang which is interesting... gosh, it's been a while since I did the security thing. > >>> So if a plain method (ie. void method()) is part of a class in the Sun > > JDK [quoted text clipped - 25 lines] > java.lang.SecurityException: Prohibited package name: java.lang which is > interesting... gosh, it's been a while since I did the security thing. Classes in packages starting with the string "java" can only be loaded by the bootstrap classloader, which on Sun's JVM gets its classpath from the -Xbootclasspath parameter (right now; subject to change whenever Sun feels like it) and from the JVM's installation path. This allows, for example, containers to provide implementations of javax.servlet via the bootstrap classpath, even though that class is neither part of the JRE library nor allowable from the default classloader or its other children. > I know but what I am saying is if you write a 3rd party app and create a new > java.lang.ThreadGroup you can't use it's method "void add(Thread t)" You would be able to if your class is also in the package java.lang. But because the java.lang-package is special and the compiler won't let you compile classes with that package "you" (as long as you're not working on the Java-compiler) are not able to access that method. If you write a new mypackage.ThreadGroup-class that derives from java.lang.ThreadGroup (I'm not sure if ThreadGroup isn't final but that would make no difference here) you can't access that method, either because it's only package visble and not protected or public. To go back to your problem. Why do you want to access that method at all? Regards, Lothar SignatureLothar Kimmeringer E-Mail: spamfang@kimmeringer.de PGP-encrypted mails preferred (Key-ID: 0x8BC3CD81) Always remember: The answer is forty-two, there can only be wrong questions! >So if a plain method (ie. void method()) is part of a class in the Sun JDK >it's basically private? No. It is visible to all the classes in the package. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com >Is a plain "void method()" public, protected or private by default? it is "default" by default. Unfortunately there is no keyword to explicitly state you want the "default" scope, and not official name for the default scope other than "default". It is a bit like saying you bought a "default-coloured" car, but the car manufacturer refuses to refer to the colour by any name other than "default" in its literature. It is sometimes called "package" scope, but you can't use the package keyword. see http://mindprod.com/jgloss/scope.html SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com >Is a plain "void method()" public, protected or private by default? Your question implies you have big hole in your knowledge. It will take a long time to fill it by asking individual questions on a newsgroup. Instead get a text book and read up on scope. Then ask questions about what still does not make sense. You can also read my more informal essays on scope. Start at http://mindprod.com/jgloss/scope.html and follow the links. I recall wrestling with this long ago, doing experiments, and finally deciding it was all trivial and obvious. Oddly, I have yet to figure out a way to explain it all that makes its obviousness immediately apparent. Have faith that you will have some aha moments and you will wonder what all the fuss as about. Anonymous classes are another matter. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com > >Is a plain "void method()" public, protected or private by default? > [quoted text clipped - 20 lines] > The Java Glossary > http://mindprod.com Well the package private is barely ever used and I'd say 99% of methods have a named access modifier >Well the package private is barely ever used and I'd say 99% of methods have >a named access modifier I think you are overgeneralising. Consider a large but simple class like java.lang.String: I counted 78 public, 4 default, 2 private.. Consider a more complicated class like java.util.Pattern, you see a quite different distribution: 163 default, 69 private, 9 public. Consider a simple standalone 1-class application, designed to do work, rather than provide services to client: 8 private, 1 public. Default is common when you have a complicated problem with mulitple classes and lots of interaction between classes. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com I've just released what package private actually is - it's the old basic method (like in many old procedural languages) that didn't include method security - limited to the working folder. >I've just released what package private actually is - it's the old basic >method (like in many old procedural languages) that didn't include method >security - limited to the working folder. Learning Java is much like learning a foreign language. The sooner you start learning to think in the language, rather than think in your native language and translating, the better command of the language you develop. This is even truer of Java than most other computer languages because Java is so strongly idiomatic. There are canned ways of doing almost everything. You build very little from scratch from the primitive elements. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com > Is a plain "void method()" public, protected or private by default? None of the above. It is 'default.' Its visibility is restricted to classes in the current package, and subclasses in other packages. -- Adam Maass "Crouchez" <safdfasdf@asdfasdfs.com> wrote: >> Is a plain "void method()" public, protected or private by default? > None of the above. It is 'default.' True. > Its visibility is restricted to classes in the current package, True. (Although "its own" would be a better adjective than "current".) > and subclasses in other packages. False. That would require protected access. SignatureLew Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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