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Java Forum / Tools / December 2003can't import class in default package???
Hi: I have a java fiile that resides at the default package under src folder. In the same project, when I want to import that class, I just need to type import ClassName right? However, eclipse cannot resolve it. But I can see the class in the automatic code completion pop up list if I just type the first 1 or 2 letter of the ClassName. So what should I do to import such class? thanks, -Kay > I have a java fiile that resides at the default package under src folder. In > the same project, when I want to import that class, I just need to type [quoted text clipped - 6 lines] > > So what should I do to import such class? You should put the class into a package, instead. As of JDK1.4 the above won't work with javac either.  SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too >>I have a java fiile that resides at the default package under src folder. In >>the same project, when I want to import that class, I just need to type [quoted text clipped - 9 lines] > You should put the class into a package, instead. As of JDK1.4 the > above won't work with javac either. I noticed that. But I don't know who thought it would be a good idea. --Mike Amling > >>I have a java fiile that resides at the default package under src folder. In > >>the same project, when I want to import that class, I just need to type [quoted text clipped - 11 lines] > > I noticed that. But I don't know who thought it would be a good idea. The creators of Java. Quoting from the JLS: "For small programs and casual development, a package can be unnamed or have a simple name, but if code is to be widely distributed, unique package names should be chosen. This can prevent the conflicts that would otherwise occur if two development groups happened to pick the same package name and these packages were later to be used in a single program." "Unnamed packages are provided by the Java platform principally for convenience when developing small or temporary applications or when just beginning development." The problem becomes complicated when you start thinking of multiple hierarchies in the class path. For example, if I have a program in multiple jar files and a class uses a class in a class in an unnamed package.Where would it get it from? From the root of the jar file that class is in or from the root of the jar file of the class from which the program started? Conceptually, you could have multiple unnamed packages. -- Dale King The only reason I put it at the default package is that it's a JNIed Class by someone else. If I put it to my own package, I'll have to reJNI. And it's a pain because I am not sure I can get it compiled successfully. -Kay > The only reason I put it at the default package is that it's a JNIed Class > by someone else. If I put it to my own package, I'll have to reJNI. And it's > a pain because I am not sure I can get it compiled successfully. Well, you may be able to work around, however painfully, by using a Middleman class as your startup class, and using the JNIed class through an interface. /* no package here */ import JNIedClass; // The class you can't recompile in a package. import com.kay.JNIedInterface; // New interface that you write. class Middleman implements com.kay.JNIedInterface { private JNIedClass passthru=new JNIedClass(); public static void main(String[] args) { com.kay.MainProgram.jniProxy=new Middleman(); com.kay.MainProgram.main(args); } public void jnicall() { passthru.jnicall(); } } ----------- package com.kay; public interface JNIedInterface { void jnicall(); } ----------- package com.kay; /* Your old class that can't call JNIedClass directly. */ public class MainProgram { public static JNIedInterface jniProxy; public static void main(String[] args) { jniProxy.jnicall(); ... } } --Mike Amling >>>>I have a java fiile that resides at the default package under src > [quoted text clipped - 39 lines] > the root of the jar file of the class from which the program started? > Conceptually, you could have multiple unnamed packages. That's all been true since 1.0.3. --Mike Amling > >>>>I have a java fiile that resides at the default package under src > > [quoted text clipped - 41 lines] > > That's all been true since 1.0.3. There is no such thing as 1.0.3. Java went from 1.0.2 to 1.1. And I fail to see where I put any limits on when that was true. What has not been true is that javac would not compile a file importing from the default package. That did not happen until 1.4. There were other compilers, most notably Visual Age for Java that did not support this as allowed by the JLS. -- Dale King > The problem becomes complicated when you start thinking of multiple > hierarchies in the class path. For example, if I have a program in multiple > jar files and a class uses a class in a class in an unnamed package.Where > would it get it from? From the root of the jar file that class is in or from > the root of the jar file of the class from which the program started? > Conceptually, you could have multiple unnamed packages. This "problem" isn't tied to the default package only. Whenever you have the same fully qualified class in several jars, the JRE needs to decide what version to use. The default ClassLoader will use the one mentioned first in the classpath. Ville Oikarinen > Hi: > [quoted text clipped - 8 lines] > > So what should I do to import such class? In theory, if the class is in the default package, you shouldn't have to import it. You are using the fully qualified name already. Ray >> Hi: >> [quoted text clipped - 13 lines] > > Ray Standard programming practices say that the default package is only used for simple programs. Any multi-packaged programs you make should be defined in their own packages, that have descriptive titles so that another programmer 4 years down the road can pick up your project and pick up where you left off. Andrew A detailed discussion is can be found in the bug report: http://developer.java.sun.com/developer/bugParade/bugs/4361575.html I think login is required Moshe > Hi: > [quoted text clipped - 11 lines] > thanks, > -Kay > Hi: > [quoted text clipped - 11 lines] > thanks, > -Kay you don't import things from the default package, that is why it is called the default package everything is already imported by default > > Hi: > > [quoted text clipped - 11 lines] > you don't import things from the default package, that is why it is > called the default package everything is already imported by default Wrong on two counts. First it isn't called the default package. It is called the unnamed package. And nothing from the unnamed package is imported by default. They are visible to other members of the unnamed package since they are in the same package, but they are not visible to compilation units in other packages. -- Dale King 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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