Introduction
I am using NetBeans 9.0 with imported libraries (JAR files). Some of those I downloaded from a school's computer and others from home.
Problem
When I want to do the build it shows an error that it can't reach the library, even worst, I can not even remove libraries by some reason. Not even "manually" (enter the file's project and manually delete it).
In this picture you can see the build error log for some imported libraries (jsoup and jfreecharts) which by some reason can not be read.
On the right of the image you see the Edit for JSoup which shows a different path to the JAR file.
Question
Why is NetBeans still looking for the previous path?
How I am supposed to solve this path problem when I can not even remove libraries?
How I can avoid this problem in the future?
Not using NetBeans won't be accepted as an answer.
Thanks for your interest and time.
Head over libraries in your project
Right click on it with your mouse and then into properties
This will set you into Categories: -> Libraries.
(Already solved the path issue that is why there are no red paths here)
There you can see all the classpaths of your libs and if those are correct. Delete those which are on red and reimport the JARs into your project.
Click on the path you want to delete and press Remove
This will solve the issue AND be able able to delete libraries that you are not using anymore.
I want to use the Light Weight Java Gaming Library(LWJGL) to my Netbeans so I can use it in my Java application. The only videos that I can find show the zip file that they downloaded with separate src and doc folders inside of it. The zip file that I download has everything in one directory. I went to lwjgl.org/download and clicked on Stable and then Generate Bundle. What am I missing?
I had the same problem recently.
So, to begin you want to go to Tools in the context menu and select Libraries (as shown). Next you can add a new library and name it e.g. LWJGL-3.1.1 confirm with ok. You can find 3 tabs in the current window Classpath, Sources and Javadoc. There you add your jar files accordingly (in the downloaded .zip file you find .jar files with different names like lwjgl-{whatever}-sources.jar or lwjgl-{whatever}-javadocs.jar) make sure you put them in the right place. You have to repeat this process for all of the jar files you want. The javadoc files are not required but recommended. Make sure you also collect all the native .dll files and merge them in a folder called \natives. You find them in these jar files that are called like: lwjgl-{whatever}-{your-OS}.jar.
Once you have finished the setup for your library right click on your current project and choose Add Library.... In the window that pops up you scroll down until you find your library that you have just created and you are almost done now.
Last but not least go to the project settings. Select Run and make sure that you set the classpath in VM options to something like in the image: -Djava.library.path="C:\java_workspace\LWJGL Library 3.1\natives. Now this classpath tells netbeans where your native files are located. Your \natives folder that you should have created in the beginning is where this path should lead to. That's it. This is all you have to do for a setup without the use of maven, gradle, ...
You can test if it is working with the code provided by LWJGL HelloWorld example.
I hope this solved your problem.
Best regards.
I'm posting this query after doing lots of googling and trying out different options for last few days. Is there an easy way to attach source in Eclipse? is the closest answer I found to my question.
From above post, I tried all solutions but each time Eclipse is opening .class file instead of .java file.
Eclipse Details:
Kepler Service Release 2
Build id:20140224-0627
Please let me know if this is a bug with Eclipse or if I am missing something.
If you are using Maven, try this:
Double click on your project in eclipse -> Maven -> Enable Workspace Resolution
This is most likely because Eclipse actually use the class file for declaring the item you have requested the declaration for, and not the source file you think it should be using.
The typical reason for this is if you have a jar file containing previously compiled classes on your build path before (or instead) of the project containing the source you want. This is very rarely desirable as it can take quite a while to discover that your edits do not take effect.
Examine your build path carefully and ensure it is as you want it to be.
Maven is likely supplying a Classpath Container to your project, and generating entries for the Java Build Path based on the pom.xml contents (the JRE System Library is another example of this). Its entries will not have source attachment unless the container decides it will, which is why the Installed JREs preference page offers to let you set Source Attachments. If the pom.xml has something like that, see if you can use it. If not, see if you can configure the Maven container from its context menu. Otherwise, you may simply be stuck.
I had this same problem: when I pressed F3 or tried to open Declaration (after right click) for any element, it took me to the bytecode .class file.
My solution:
I went to the project in Project Explorer:
right click on project name->Properties
Then in Porject Properties window,
Java Build Path->"Order and Export" tab
There I selected the folder with the .java files (source code), which was below the folder having the .class files -in my case "JRE System Library [java-11-openjdk-amd64]", and pressed 'Top' button on the right frame. Then the folder with source files moved to the top.
Finally, pressed "Apply and Close" button.
That solved my problem forever and ever.
The folder
I installed a plug-in which allows me to download the sources for a maven project.
I'm not by my develop machine right now, but I think it was this:
http://marketplace.eclipse.org/content/m2e-dynamic-sources-lookup#.U8gjGWIaySM
With this, you can select a project an have maven download the sources and make then available when you navigate the code in Eclipse. All without "leaving" Eclipse.
Check into your project modules the Java Build Path, look inside the Source tab and verify if you have "Allow output folders for source folders" checkbox flagged; in this case you just need to uncheck it and you will be able to see again the right source from java files.
This is related to the Call Hierarchy in Eclipse IDE.
If you are in a situation, where you're seeing duplicate methods inside the call hierarchy showing Members calling 'myMethod(...)', double-clicking on one of the listed methods may open the .class file instead of the .java file.
When this happens, the solution is to set the search scope in the call hierarchy to Project instead of Workspace.
After setting the search scope, you won't be seeing duplicate methods listed in the call hierarchy, and double-clicking on the listed methods will only open the .java files.
(Using Eclipse DevStyle Dark Theme)
I have no idea why, but from today Eclipse doesn't compile .java files into .class. I press the "Run" button and Eclipse only tries to run the program rather then compiles it first, so i get this error all the time:
Exception in thread "main" java.lang.NoClassDefFoundError
open problems view from window -> show view -> problems, if there's any error, fix it
eclipse will reject to compile if there is any problems in your project
Close Project -> Open Project -> Clean -> Refresh
Hope it helps for someone else
This problem happens when "for some reasons" your project is corrupted and has a red icon near the project's name in Eclipse. The solution is to save the project's folder, delete the project in Eclipse, than create the project again in Eclipse coping all the previous files saved.
I ran into this problem with Eclipse Luna, for some reason the Java builder was missing from the project. Verify that in your .project file you have something like
<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name>
<arguments>
</arguments>
</buildCommand>
</buildSpec>
You can also configure builders from Project Properties -> Builders
When I have had this exact same problem, its cause has always been the same and the solution has worked 100% of the time for me. It's caused by a missing jar file in the project's Java build path and it's indicated by a red exclamation point decoration on the project icon. To fix the problem, go to Project|Properties|Java Build Path, click on the Libraries tab and either remove or fix the path for all missing jar files. If your project is configured to rebuild automatically, it should start a build as soon as you apply your changes.
The eclipse needs to erase the output folder when building classes.
The folder is found on Project Properties -> Java Build Path -> Default Output Folder. It can differ from general output folder name found under Eclipse Preferences. If this output folder cannot be erased for some reason (for instance, on Windows, when a shell is opened on this location), the project is marked as corrupted (as Marco Micheli describes) and the classes then are not built.
You just need to make sure the output folder can be erased.
Yes I was facing this issue. Coz Eclipse cannot build the project for Build Path error. Check that your external jar files is not showing any error. Delete the Jar file which one is missing or which one is showing re color. delete that one. add a fresh one from the correct path or location. if all the error are gone. then in the project bin folder one class file will be created and then could not load main class error will be removed too.
there can be errors in your project, or other reasons like mentioned in above answers.
or you may be a fool like me
who moved the source code to other folder and not updated source path in project build properties. in this case it was not giving any error or class files too.
check that too.
goto
Project Properties -> Java Build Path -> Source
Add or Link new source folder location.
Do clean all projects ! This will erase all old class files, so eclipse is forced to generate them again.
Some times jars in the build path might be missing even though we are not using it. Since error is there, java files wont compile into classes.
Can check errors from problems view.
Either remove jars from build path or place the missing jars in the build path.
I had problem in eclipse for load module not found and no class file was getting created.
Solution: Go to Create New Project > Under JRE section Choose Use project Specific JRE.
Now Class files are created.
Please check if all the jars are there in your build path settings.
If any jar is missing this issue might come.
I had this problem, I tried the clean, the build manually, open, closing the project, deleting, and open, etc., nothing works, and after 4 hours I get a workaround what works for me.
Please, Make a RAR, ZIP, or copy from your entire project folder as a backup if it doesn't work and you mess around, OK, now:
Clean the Project. It cleaned all my class files from the output folder, but doesn't generate the class files after the clean with the building (but we already know that)
Delete the project (warning, make sure the Delete contents is not selected or your project will dissapear). For me it says something about that desynchronysation with code mix, and hibernate, blabla)
Close myEclipse
Restart your computer.
Open myEclipse
Import the project with the option "Projects from folder or Archive", not with the "existing projects into workspace" option.
Myeclipse start to build the class files, I don't know why, but works for me, I hope this helps somebody else.
Also ensure that there are no projects with fatal errors (projects with ! symbol over it) in the build path of the project which is not generating classes under the bin directory
Just restart your machine.
Its weird but it helps we had loads of problems this type in our company for unknown yet reason. Always restarting the machine helped.
It was normally encountered while trying to run Junit tests and it could not find a class even when the Run configuration was pointed to /bin.
I encountered a similar problem: previously compiled and running java files couldn't run anymore. Eclipse showed "couldn't find class xxxx". When I checked bin folder, the previous .class files were gone. That's why Eclipse couldn't run the files, NOT because of errors in files. I don't know why it can't just re-compile the file, and why the .class file gone missing in the first place.
But I found a solution:
Simply create a dummy java file in the same package (without doing anything just create), then run it. Then magically all previous .class files came back. And I can run those files as before.
Just Remove Your all Jars (Libraries) from the Build Path and refresh and add all jars and clean and build the project
This is probably a rare event but I declared a servlet with annotations and left off the "/" before the servlet mapping name. I spent over an hour chasing my tail, installing new servers, thinking I might even need to re-install my IDE and it was this simple error! Every time I tried to load any page from my Dynamic Web Project I got a 404 error. I could not even load a plain vanilla html page. There really needs to be better error logging with the IDE and Server interaction as there was zero indication of the error and my servlet was never called at the start of my web app. Hope this helps save someone else some frustration. Always name your servlet with a / slash like /myServlet never just myServlet.
I tried many different potential solutions: cleaning, rebuilding, removing, re importing, Update Maven Project and nothing. I still couldn't run my app from Eclipse. In my case the reason was that I was running Eclipse using openjdk-11 while my project was in Java 8. After I've reconfigured Eclipse to be ran from Java 8 everything started to work (in eclipse.ini).
-vm
/usr/lib/jvm/jdk1.8.0_202/bin
I'll explain my solution to this problem: "eclipse not compiling java files into class files". I'm using Eclipse version '2020-03 (4.15.0)'. I have a project that is dependent on a java project. For the dependent project, I was not able to export a jar file containing the compiles classes and resources. To be more precise, the exported jar file did not contain any class files. The output bin folder for the project is empty after doing a project build. In examining the console output when I tried to build all projects indicated that the build failed because the dependent project was missing. In looking at one of the log outputs, I saw something indicating that the build failed because some eclipse class was missing.
One of the things I tried was to do an eclipse update. Eclipse offered up the list of changes and I tried to apply them, but the update failed. I tried to update several times but they all failed. Looking more carefully at the offered up list of updates I noticed that one of the suggested update involved "deleting" Java Development Tools. That line had an warning indicating that the entire feature could not be deleted due to other dependencies and that only the non dependent features would be deleted. Doesn't that sound suspicious. Why was the update trying to delete Java Development Tools? My speculation is that something got deleted from the Java Development tool that was causing the build process to fail. The missing class I saw earlier also suspiciously sounds like it might be part of the Java Development Tools feature.
So what I did to solve the problem was to reinstall eclipse. I used the eclipse loader application to do the reinstall. (Note, I did not uninstall it first). After the reinstall, the dependent project was able to produce classes, and things once again worked as they should.
I certainly don't know how the eclipse release got into this compromised state, but in my situation the re-install of eclipse was the only way I could find to resolve the problem.
There would be the case : if you have opened project explorer in eclipse then it may not show you classes generated under /**/build/classes, in such case open Navigator view of that project and check build directory under the same project.
I just installed Netbeans IDE. I am now unable to import any org.* libs and it just says package org does not exist.
Also, I imported jdic.jar into the project and even though the code completion suggestions show up as org.jdesktop.*, it shows the same error.
How do I fix this?
Clearing the cache fixed it.
In windows 7 the cache is located in
C:\Users\username\AppData\Local\NetBeans\...
On Linux, the cache is at:
/home/username/.cache/netbeans/...
On clearing the cache, and restarting netbeans, it started to recognize org.* imports again.
I did it easily, just click the Jframe, on Navigator tab, right-click -> Set Layout -> Absolute Layout and YEP, It works for me.
org.netbeans.lib.awtextra is part of the AbsoluteLayout library. It should be added automatically by the ide whenever absolutelayout is used in the form. But if you switch to some other layout after using absolute layout, then the jar/library will be removed from the classpath and existing code making calls to the library will not compile.
If you would like to use absolute layout, then please include the library in the project. Select 'Libraries' node in the project, right-click and select 'Add Library' and select 'Absolute Layout' library from the list of available libraries.
If you do not wish to use absolute layout, then it is best to uncomment/remove code relying on the library and re-do the form design using the new layout.
Can you try importing
import org.xml.sax.Attributes;
This is part of the JDK. If you can't find that, something is really wrong.
I suspect you need to add the libraries to your maven pom.xml file.
You should redirect all the lost .jar files by exiting netbeans, then reopening it. There should be a prompt asking you to help the IDE find the .jar files. So please do so. If you aren't able to find the jar file. Clean and build the individual packages. There a new directory called a dist directory will be created in the package directory. Now you can redirect them.
Above was not working for me so I tried below and its working:
Google "absolutelayout.jar download"
Download jar
Open NetBeans and Add this "AbsoluteLayout-RELEASE***.jar" file to your project Library folder.
now try to run the project/file
in my experience the problem was with a Jpanel with AbsoluteLayout, I put free-design and solved the problem