So recently I was bombarded with the below error.
I have a very bad understanding of Java and how the internal memory location and file compiling work. So, when I ran my program(every program gave me the error so I guess it doesn't matter which program I ran and for that matter, I didn't include it here), it started giving me this error. I looked if there were any errors with my classpath and working directory, but still, after applying those too it didn't help much, and I still got the same errors.
The programs ran from the terminal using commands but from the normal "Run" function, it gave me this error.
I just restored the default setting of the IDE and it now works.
The difference I found was that after restoring the default settings, the project location was the default folder- IdeaProjects- whereas when I encountered the error I used to set my own location for the projects. Is it due to this? I had the same kind of problem in eclipse when I set the location of the project outside of the eclipse workspace.
Is the location of the project simply the reason I got the below error and if so why? I just don't understand how the internal mechanism of the whole programming thing works. About the directory, memory allocation, etc. Can anyone provide some decent materials after which I can be at a stage where I can separate what is the error and why is it causing or why the program doesn't run?
Full error:
/Library/Java/JavaVirtualMachines/temurin-17.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=57983:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Users/(myname)/Desktop/Folders/College/2nd sem/CS 2/Labs:projects/Lab3/Lab3dot34.0/out/production/Lab3dot34.0:/Users/(myname)/Desktop/Folders/College/2nd sem/CS 2/Labs:projects/Lab3/Lab3dot34.0 Main
Error: Could not find or load main class Main
Caused by: java.lang.ClassNotFoundException: Main
Initially, I tried to view the working directories and add/change the classpath from the project structures like every suggestion found on the internet but still, the error existed.
So I was making a java program in Netbeans IDE 8.2 and when I tried to run it, I got this error:
Error: Could not find or load main class helloworld.HelloWorld
C:\Users\name\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 1 second)
(Assume that helloworld is my project name and HelloWorld is my class name)
Everything was fine before, and I can't think of what I did that would cause this error to happen. This is the first time this error has happened to me so I don't know what to do. The code doesn't seem to have any errors.
Other projects of mine seemed to also have the exact same problem even though I haven't opened or edited them in weeks prior to this error occurring.
I tried many other ways but none of them seems to do the trick. Including deleting the cache folder and setting the main class through the properties tab.
Here's a screenshot of my code with the error, my name is crossed out:
Even if I type my code directly in the main class, which is class6homework.java, the error still occurs but it says class6homework.class6homework instead of the one in the screenshot.
Any ideas on how I could fix this?
UPDATE: I got it to work by moving the folder that contains the project to my desktop, didn't know why it wouldn't work in my original location. Thanks for the help.
Perhaps you don't have the main method included. If that is not the problem, try right clicking your class in the project tree and look for an option that says "Set as main class" or something like that
Possible Fixes:
Fix 1
Go to project properties (right click on the folder of your project in netbeans)
On left tab where it shows the categories, click on the "Run" selection
Then click on Browse to find the Main class you use on your project
Fix 2
Go to C:\Users\name\AppData\Local\Netbeans
delete the Cache folder.
Rebuild and Run
Fix 3
Download most recent version of Netbeans
Fix 4
Download most recent version of JDK and configure Netbeans to use that
So I'm running into a Jar hell problem when trying to run individual integration tests, using -Dtest=, that runs as a ESRestTestCase (ESTestCase). The issue here seems to be that some elasticsearch classpath validation class requires target/classes to exist. However, this project is only for testing so that requirement doesn't make sense.
This happened with Elasticsearch 7.0.0 and Java 1.8.0.251. Not sure if this is a problem with later versions.
java.lang.RuntimeException: found jar hell in test classpath
at org.elasticsearch.bootstrap.BootstrapForTesting.<clinit>(BootstrapForTesting.java:98)
at org.elasticsearch.test.ESTestCase.<clinit>(ESTestCase.java:229)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at com.carrotsearch.randomizedtesting.RandomizedRunner$2.run(RandomizedRunner.java:623)
Caused by: java.nio.file.NoSuchFileException: <MY PROJECT FOLDER PATH HERE>/target/classes
at sun.nio.fs.UnixException.translateToIOException(UnixException.java:86)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107)
at sun.nio.fs.UnixFileAttributeViews$Basic.readAttributes(UnixFileAttributeViews.java:55)
at sun.nio.fs.UnixFileSystemProvider.readAttributes(UnixFileSystemProvider.java:144)
at java.nio.file.Files.readAttributes(Files.java:1737)
at java.nio.file.FileTreeWalker.getAttributes(FileTreeWalker.java:219)
at java.nio.file.FileTreeWalker.visit(FileTreeWalker.java:276)
at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:322)
at java.nio.file.Files.walkFileTree(Files.java:2662)
at java.nio.file.Files.walkFileTree(Files.java:2742)
at org.elasticsearch.bootstrap.JarHell.checkJarHell(JarHell.java:199)
at org.elasticsearch.bootstrap.JarHell.checkJarHell(JarHell.java:86)
at org.elasticsearch.bootstrap.BootstrapForTesting.<clinit>(BootstrapForTesting.java:96)
... 4 more
At first I tried various methods for making sure the classes folder was still created. I ran into new problems that seemed fixed in later versions so I upgraded to Elasticsearch 7.6.2 (And lucene 8.4.0). Upgrading seemed to remove the need for the folder to exist but triggered other issues (similar to this). I worked around such issues with -Dtests.security.manager=false. Then I got thread leak issues which I "solved" by setting #ThreadLeakScope(ThreadLeakScope.Scope.NONE) on the test class.
Then finally it seemed to work when running maven in command line for individual tests. But when trying to run the maven task with debugger in Intellij the debugger does not seem to attach.
So I try to run it as JUnit templated test in Intellij. Here I get jar hell when running it but it works to debug. The jar hell was later solved by setting idea.no.launcher=true in idea.properties.
Alright, good enough for now. These workarounds are far from ideal but it works for my current purposes. A lot of things will change before moving into mainline anyway. And maybe this will help someone else. Hopefully I can post a better solution later.
I am trying to debug a Java / Maven project with a lot of depencies on various libraries.
When I run it on a Linux server the program starts up fine, but when I try to run it in Eclipse it throws the following exception:
Exception in thread "main" java.lang.NoSuchMethodError: org.apache.camel.model.RouteDefinition.getErrorHandlerBuilder()Lorg/apache/camel/ErrorHandlerFactory;
at org.apache.camel.spring.spi.SpringTransactionPolicy.wrap(SpringTransactionPolicy.java:69)
at org.apache.camel.model.PolicyDefinition.createProcessor(PolicyDefinition.java:133)
at org.apache.camel.model.ProcessorDefinition.makeProcessor(ProcessorDefinition.java:437)
at org.apache.camel.model.ProcessorDefinition.addRoutes(ProcessorDefinition.java:183)
at org.apache.camel.model.RouteDefinition.addRoutes(RouteDefinition.java:817)
at org.apache.camel.model.RouteDefinition.addRoutes(RouteDefinition.java:165)
at org.apache.camel.impl.DefaultCamelContext.startRoute(DefaultCamelContext.java:697)
at org.apache.camel.impl.DefaultCamelContext.startRouteDefinitions(DefaultCamelContext.java:1654)
at org.apache.camel.impl.DefaultCamelContext.doStartCamel(DefaultCamelContext.java:1441)
at org.apache.camel.impl.DefaultCamelContext.doStart(DefaultCamelContext.java:1338)
at org.apache.camel.impl.ServiceSupport.start(ServiceSupport.java:67)
at org.apache.camel.impl.ServiceSupport.start(ServiceSupport.java:54)
at org.apache.camel.impl.DefaultCamelContext.start(DefaultCamelContext.java:1316)
Now, I can see that the RouteDefinition class is in the camel-core-2.9.3,jar and I can see that this library is imported. So how come it doesn't see that method?
How do I go about debugging this?
Could I get info from the process running on the Linux server? For example can I get the list of Jars that are imported and the order in which they are imported?
Many thanks!
The error that you're getting is caused by Maven pulling in the wrong version. Try deleting all versions out of your local repo, add it explicitly to your pom, clean out all of your builds, pray to the eclipse gods, etc. If it still gives you the error, check your local repo to see which wrong versions it pulled in, figure out what depends on them, and add explicit ignores for them while keeping the explicit include.
My Eclipse (Indigo) was running just fine. I created a simple class Hello. It is placed in package cont in the folder ch13. However, when I try to run it from Eclipse I get info from Java Virtual Machine Launcher:
Could not find the main class: cont.Hello.
I tried to run other classes from this package and they run just fine (that is the classes that existed there before). However any new class I create in this package has these problems. Actually any new class I create in Eclipse runs into this problems. I decided to check how it works from the command line. It seems that the problem still exist - I get same error. I checked the path and it is C:\Program Files\Java\jdk1.7.0_02\bin, which is correct (note the other classes are running from Eclipse just fine). I tried to run with java -cp . Hello and there are some Errors produced starting with java.lang.NoClassDefFoundError: Hello (wrong name: cont/Hello). Code itself is simple:
package cont;
public class Hello {
public static void main(String[] args){
System.out.println("Hello");
}
}
How can I fix it so that my classes still run under Eclipse?
.metadata is corrupted.
Steps:
Warning: Deleting .metadata will delete all your Eclipse configurations, plugins, project setups. Make a backup before you attempt this!
Stop eclipse, delete .metadata in workspace and restart eclipse
Import Project
Run again
Removing the Run Configuration
Sometimes I have a similar problems in some pre-release versions of eclipse. For fix the error, I delete the Run Configuration. You can find that in menu Run, Run Configurations...
Then I launch the app with Alt+Shift+X, then J. If this don't work, Ctrl+F11.
Deleting the .metadata directory
In another way, the configuration settings for your current workspace may are corrupted. Those settings are in the .metadata directory in your current workspace 1. In that case, there is no other choice than delete the directory:
Close eclipse.
Delete the .metadata directory.
Start eclipse.
Import the projects.
Run the project again.
Notes
You will see that directory with File > Switch Workspace > Other...
I have solved the issue following way:
Go to Run Configuration (Right Click on Java File->Run->Run Configuration).
Go to ClassPath Tab:
Click on Advanced -> Add Folders -> Add bin directory (which has class file in it for Java source code)
Re run the code, now it will solve the issue. It worked for me
Note: This worked in the past and I received many up votes. Perhaps this is not a solution anymore - but it once was - as the eclipse version was indicated.
Problem
This can also be caused by a Java Build Path Problem.
In my case, I had a an error:
A cycle was detected in the build path of project {project}. The cycle consists of projects {x, y, z}.
This can occur when you include other projects in the build path of the project you wish to run. In fact, all the projects will fail to run with the error
Could not find the main class: Example.class
Solution
Open
Windows -> Preferences -> Java-> Compiler -> Building -> Build Path Problems
Uncheck the Abort build when build path errors occur toggle
This seems like a can of worms if you end up with other build path errors I image. So use with caution.
Note: This only works if you have a "cycle error". This error message can be found in the "Markers" tab
I found the solution to this here
Info
Java 1.8.0_152
Eclipse Photon (June 2018)
Renaming the main class should be enough (and easiest):
- Go to your class and set cursor to your class name;
- ALT + Shift + R and rename the class (build if not done automatically);
- You should be able to run it now;
- Rename the class to the old name if you want;
You must have main function in your class. Like
public class MyDataBase {
public static void main(String args[]) {
}
}
I had this same problem in a Maven project. After creating the src/test/java folder within the project the error went away.
Another tip: I initialized static fields in a wrong order - surprisingly it didn't bring up a Problem (NullPointerException?), instead Eclipse complained with exactly the message OP posted. Correcting the static initialization order made the class run-able. Example:
private static ScriptEngineManager factory = null;
private static ScriptEngine engine = null;
static {
engine = factory.getEngineByName("JavaScript");
// factory is supposed to initialize FIRST
factory = new ScriptEngineManager();
}
I found the way to fix this problem was to rename the project. If you give it a name with strange characters (in my case, :), it will have trouble locating your class. I don't know if this rule applies to numbers, but try renaming the project or making a new one and copying the files. Name it without any numbers or special characters.
I solved this error by closing the project, removing it from eclipse and then importing it again.
Might be a little simpler than to redo the whole workspace setup.
I had this issue after upgrading to the Eclipse 2019-12 release. Somehow the command line to launch the JVM got too long and I had to enable the jar-classpath option in the run configuration (right click on file -> run as -> run configs).
I read so many blogs and tried so many tricks but my problem not resolved. I was able to run the code but not able to generate the jar file. :( Sad..
But I tried something which might be very silly but worked for me and bought eclipse on trace. What I did was..
Just deleted the main method from the class. Saved it. Did undo to bring the main class back. Tada... Issue resolved...
Just one think would like to say, keep your eclipse in "Build Autometically" mode.
Move your file into a subdirectory called cont
Standard troubleshooting steps for Eclipse should include deleting and re-importing the project at some point, which when I have dealt with this error has worked.
I solved my issue by doing this:
cut the entire main (CTRL X) out of the class (just for a few seconds),
save the class file (CTRL S)
paste the main back exactly at the same place (CTRL V)
Strangely it started working again after that.
It is possible to have 2 groovy-xxx-all.jar files by excample in lib directory. which makes that an app is not running
I had the same problem, this is my solution:
I manually deleted the bin folder of the project
Then I refreshed the project which recompiled the whole project and created a new bin with all .class files
I did it because when I performed Clean(project->clean) my .class files were not getting deleted. the above solution works for me hope its useful to others.
I had the same problem.I solved with following command maven:
mvn eclipse:eclipse -Dwtpversion=2.0
PS: My project is WTP plugin
If you are using a pre-defined run configuration, go to classpath and try "Restore Default Entries". This will reconfigure the classpath for that configuration.
This worked for me finally :
RUN -> RUN CONFIGURATIONS -> DELETE THE RUN CONFIGURATION
CLOSE ECLIPSE
REOPEN ECLIPSE
CREATE RUN CONFIGURATION AGAIN.
Tadaaaa !! It works