I have two jar files - jar1 and jar2. Both of them are located in C:\Eclipse projects\ and I have added the paths to both of them to the Environment Variable CLASSPATH as follows
.;C:\Program Files\Java\jre6\lib\ext\QTJava.zip;C:\Eclipse projects\stdlib.jar;C:\Eclipse projects\algs4.jar
the ".;" at the beginning were there so I left them. Then I added the jars to the project from their location C:\Eclipse projects\ and they showed up as Referenced Libraries. However, when I try to instantiate a class from the jars it does not recognize it. I am also not able to import the jar (import jar1).
After I tried adding a lib folder in the project and I added the jars there. After, I added them as references once again (so not they appear twice in the Referenced Libraries), however, I am still not able to use the inner classes. Any help will be much appreciated.
UPDATE:
Something must be wrong on my end. None of the suggestions worked for me. Here is a video with all the steps: screencast.com/t/gC81YzCsLY0e
RESOLUTION In my project I had a package called TestProject and it seems that those jars needed a default package. After deleting the TestProject package and using a defaultPackage everything worked correctly after adding external JARs as explained below.
I've got the same problem as you today, And no answer from the web can solve it. However, I fixed it at last.
In fact, there is nothing wrong with the setup, it is right to import those jars through "Add External JARs". The real problem is the location/package of you java code. I found that you have to put your .java file in the default package. For example, you will get errors if you put your java code in a package like com.xxx.yyy.ccc, below is an image which shows the right location/package you should use(see WTF.java). After doing that, you program will be able to run.
However, that is how i fixed my problem, i'm not sure that could work for everyone..
In eclipse, right click on a project->Propeties->Java Build Path->Add External JARs (Add JARs if the jar is inside the project's folder) and then choose your jar file.
From now you can use the inner classes of the jars you added. Eclipse will import them when you'll start using them.
Why don't you use these two JARs—— stdlib-package.jar and algs4-package.jar.
And below the code page(http://algs4.cs.princeton.edu/code/)
Q. If I use a named package to structure my code, the compiler can no longer access the libraries in stdlib.jar or algs4.jar. Why not?
A. The libraries in stdlib.jar and algs4.jar are in the "default" package. In Java, you can't access classes in the default package from a named package. If you need to use our libraries with a named package, you can use these package versions: stdlib-package.jar and algs4-package.jar.
Warning: if you are taking Princeton COS 226 or Coursera, Algorithms, Part I or II, you must use the default package verison of our libraries to facilitate grading.
Showing my test success:
If you have a folder with your JAR files into the project:
Right click on the project>Build Path>Configure Build Path;
At the tab "Libraries" click on Add JARs, search and select the JARs files you want to use.
If you have yours JAR files any other place outside the project:
Right click on the project>Build Path>Configure Build Path;
At the tab "Libraries" click on Add External JARs, search and select the JARs files you want to use.
Related
Ok the deal is, I've made a small class library (*.Jar file) to help make a more visually organized code and to help with some common tasks.
Before you tell me to go to: Tools > Preferences > Libraries.
I have done that, over and over and over again.. I also tried to manually add it to: C:\Program Files\BlueJ\lib\userlib\"jar file here"
And yes, i did restart BlueJ to load the newly added libraries.
No matter what i seem to try it won't let me import it to my project using the import command, but without it, it just won't compile.
I know i can just add the classes manually, but as the class library slowly grow, so does the effort of adding all the classes in that library.
In advance, thanks for your help and consideration.
If adding your jar file in the Preferences > Libraries tab doesn't work, you can try adding the jar to the "userlib" directory at <bluej-dir>/lib/userlib (where <bluej-dir> is the folder where BlueJ was installed).
A third option you can try is adding your jar file directly to a project by creating a +libs directory inside your project directory and copying the jar to that directory. This has the drawback that you have to manually copy the jar to each project +libs subfolder that needs your library. On the plus side, it allows you to distribute your project (library jars included) just by zipping up the root project directory.
On Windows I create directory named "+libs" on my blueJ project directory,
then add .jar to that directory, and restart blueJ ,
that´s help me, and import after that work fine
Despite the post's oldness for who stumble upon i can say with the newest version of BlueJ (actually 4.1.3) in an old Ubuntu distro(Lucid Lynx aka 10.04LTS) all work as intended per default without any hack
I decompiled a jar, imported the files into eclipse, and edited a few key java files. Whenever i try to export however, it gives me a
"JAR creation failed. See details for additional information. UHC-2.4.1/META-INF/MANIFEST.MF was replaced by the generated MANIFEST.MF and is no longer in the JAR. uk/co/eluinhost/UltraHardcore/features/core [in UHC-2.4.1] is not on its project's build path Unable to get package fragment root: UHC-2.4.1/uk/co/eluinhost/UltraHardcore/features/core/GoldenHeads.java uk/co/eluinhost/UltraHardcore/features/core [in UHC-2.4.1] is not on its project's build path" error.
I have searched far and wide for a solution, but have nor found one. I have tried refreshing the project etc, and all the necessary libraries are specified. Please help? Additional information: If I edit any other class (just add a space then delete it and then save) that class gets added to the error message as well.
I had the same issue. I noticed that all of the files that were listed as "not on the project's build path" were open for editing in Eclipse. Once I closed all of the open files, I was able to export the jar.
I assume they are locked for editing and so not exportable.
There are two issues:
It looks like you have the MANIFEST.MF file (UHC-2.4.1/META-INF/MANIFEST.MF ) so just
when you are exporting the jar file select the option for existing manifest file and point it to UHC-2.4.1/META-INF/MANIFEST.MF .
You are missing a jar file (download the UHC-2.4.1.jar from here and and add it to class path.
I know you wrote that you have all the "necessary libraries" but make sure you have added them to your class path.
Import the project from the parent folder, that's what fixed it for me.
In case you haven't noticed, they are not packages in your eclipse picture, that's one reason
I have a class called SnmpGet.java in default package. it needs a jar called example.jar. the structure of example.jar is -> degault package-> snmp.class. now SnmpGet.java makes use of this snmp.class. So now it works fine because SnmpGet.java and snmp.class are in default package. But if i move the SnmpGet.java in user defined package like com.test.Work it is not able to detect jar file. what can i do?
I need to use SnmpGet.java in user defined package only. And the jar is the downloaded one. I can not make changes to it.
First, your package does not follow the java naming conventions, no upper cases !
Do you rely on protected methods, classes, attributes...etc of snmp class ? If so, then moving your SnmpGet class to another package will cause you to lose these accesses
You may please try to add the jar(s) dependencies to your classpath. And import the packages & classes from the jar(s) that you would like to use in your SnmpGet.java file. If you are using NetBeans IDE do the following settings to add your jar(s) to your class path:
Right-click on your project folder.
Go to Properties -> Libraries -> Add JAR/Folder.
Add all the jar(s) files to your classpath.
Click on OK to finish the process.
If you are working on Eclipse IDE, you may use the following steps:
Right-click on your project folder.
Go to Properties -> Java Build Path.
Select the Libraries tab -> Add External JARs
Add all the jar(s) files to your classpath.
Click on OK to finish the process.
Hope this resolves your issues.
If you want to call protected methods of snmp.class then your class has to
subclass snmp.class (public class SnmpGet extends snmp) or
be in the same package as snmp.class
Moving the java file from . to directory ./com/test/Work requires to add a package statement to the source file:
package com.test.Work;
Then it has to be compiled (again).
Now, in order to start the application, go back to directory . (the one that contains the com folder now) and do a
java -cp .;example.jar com.test.Work.SnmpGet
(use : instead of ; if you use unix)
I'm having trouble adding a .jar file I downloaded for my Java project. This is really the first time I've used eclipse, so please bear with me and for some reason (I have no clue why), I just find it somewhat confusing.
I know that in order reference different class files you simply need to create a class library and add it to the build path. From there, all which needs to be done (unless I'm misunderstanding this for whatever reason) is use the "import" keyword to import whatever .jar, .java, or .class/.interface file necessary into the project.
I've tried that with my .jar. I have it referenced in the build path (all I did was just copy the jar to the project directory, and then use the build path option to add it externally), but when ever try to call the object "Delegator", which obviously is a part of the .jar file, it won't read.
Am I missing something here? Seriously, anyone who knows the answer to this - you're relieving a mother of a headache. And before anyone asks - yes, I've searched this one to death. I've found similar questions, but nothing which quite hit what I was looking for. Either that, or I really just lack the common sense.
Right click on project->BuildPath->Libraries->Addexternaljar and then press ok and if it doesnot worked then you should go to the Order and Export tab and checked the jar you have just added in your project. It will solved your problem.
There are several possible reasons, for the question hasn't mentioned the specific failure, and where it has occurred. The following is a list of possible reasons I could think of, but this may not be exhaustive:
You can import a class, in a different package only if the class is public. The only exception is when you are using the class in the same package. If the class is an inner class marked as private, then you're well and truly out of luck. The Delegator class in question might not be public, and that's why you may be unable to use it. This issue ought to be caught by the compiler.
The directory structure within the JAR might not match your package import statements in your classes. This might not be necessary, for Eclipse ought to provide possible fixes, but it is better to verify that nevertheless. Again, the compiler should complain if this is the case.
If the issue is at runtime, then, it is most likely that the JAR is not available in the runtime classpath. You'll need to configure the Runtime configuration, to add the JAR to the runtime classpath. Refer to the Eclipse documentation on run configurations, if you need to know how to change the runtime classpath.
Note:
Exporting the build classpath entries would matter to other projects that depend on the pertinent project; unexported entries will have to be re-imported if required in other projects. This would not apply to a run configuration.
Update
Every Java application needs a main(String[] args] method to start execution. This is the entrypoint for the application. From the comment, it appears that the main method is in a different class. If so, the said class ought to be used to start the application. In Eclipse, a "Run configuration" might be used for the class that lacks this entrypoint, resulting in the described error. One can rectify this by creating a new Run configuration for the class with the said entrypoint. This may be done by one of the following:
editing the existing Run configuration to use the desired Class (the one with the main method). See the above link, in the third bullet point. Edit the value of the class to be launched.
creating a new Run configuration for the desired Class. Usually, you'll need to traverse to the desired class, and run your application (using the Alt+Shift+X+J shortcut) from the said class.
i was facing similar issue with spring jar files but then tried with different jar files and it work so I think , classes defined in jar files were private and not available outside of jar hence you were not able to access the file .
thanks ,
Raju Rathi
Right click on the project--->Build Path--->Configure Build Path...--->In left side you have to choose Java Build Path--->Libraries--->Add External JARs--->ok--->ok
Steps to add jar file in eclipse
1. right click on project
2. click on Bulid Path->configure path
3. click on java Build path
4. Click on libraries tab
5. click on add external jar tab
6. choose jar file
7 click on ok
Copy the .jar file in libs folder which you want to add in your project.
Right click on .jar file -> Add Build Path
Done.
I've downloaded a JAR file from my teacher's website containing some classes in the default package, and I'm thus unable to access them from inside a defined package.
I have read that the preferable solution is to repackage the JAR, changing the package name. However I have no idea how to go at it. The solution probably involves using Ant or Jar Jar, but I've no experience with either tool. I would love if someone coould point me in the right direction.
Thanks.
You need to change the sources and recompile then to change the package - simply moving the class files inside the jar (or outside) does not help.
So ask your teacher to give you the sources (or to put the classes in a suitable package), or use a decompiler to do this yourself.
You can unjar/unzip them manually, create the package and jar them back using and IDE or from the command prompt like this. Also, take a look at the ANT documentation on Jar and Unjar which is quite comprehensive.
As #Piyush Instructed use the below command for creating a Jar file.
jar -cvf *.* Example.jar
If you are using eclipse, just unjar the source files into the source folder of a temporary project. Then, create a new project (the real project you will be working on), and under the java/src directory, create the package structure you want. Then it's just a simple matter of drag-n-dropping the source files from the temporary project into the correct packages in the real project. Eclipse will take care of changing the package declaration of each class for you.