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error java.lang.ClassNotFoundException when try to use OneWayAnova Class

I'm using eclipse RCP (helios), and I need to add statistics functions.
In the editor, I have no problem, no error.
But when I run or debug the project, I get:
java.lang.ClassNotFoundException:
org.apache.commons.math3.stat.descriptive.SummaryStatistics error.
first question, the library says si java 1.5+ compatible, I'm running on 1.6.
is this ok?
besides build path... is there any other way to set classpath ?
Best Regards

IntelliJ wrongly complains in Gradle Kotlin-DSL that it cannot find "java.lang.String" [duplicate]

Intellij is giving me errors all around for brand new kotlin/spring project and I cannot build or run the project from the IDE.
If I do it from the command line however, there are no issues and I can build and run the app.
'classpath' in 'org.gradle.api.artifacts.dsl.DependencyHandler' cannot be applied to '(groovy.lang.GString)'
'apply' in 'org.gradle.api.plugins.PluginAware' cannot be applied to '(['plugin':java.lang.String])'
Cannot access class 'java.lang.String'. Check your module classpath for missing or conflicting dependencie
Type mismatch.
Required:
java.lang.String
Found:
kotlin.String
Any ideas to what may be the issue?
I tried Kotlin multiplatform JVM type mismatch in InteliJ but doesn't seem to fix the issue.
UPDATE:
Cleared gradle caches, reinstalled Intellij, Import project that was created from start.spring.io with Gradle and Kotlin selected.
Using default gradle wrapper and project jdk (the path says jre)? gives me an error. Open gradle settings just opens the file explorer.
Using default gradle wrapper and machine local JDK same issues with the dependencies from above.

This issue comes up if you set up your own module inside IntelliJ and you think that since you are doing a Kotlin (Maven) project, the SDK should be set to Kotlin. Wrong!
The problem is shown in the first image. The project SDK is set to Kotlin.
Change it to Java. Probably any 8+ Java will be good enough.
This solves the IDE errors and the compiler errors as well.

Unset KOTLIN_HOME and other Kotlin- or Java-related settings you may have in your environment (env to check, unset NAME to unset.)
Then kill any Gradle daemon still running (pkill -f GradleDaemon) and test your Gradle build from the terminal. If all goes well, remove the .idea directory; restart IDEA, making sure to run it without the stray environment variables (for example, launch idea.sh from the terminal where you unset them); and re-import your project, with the choice of using the default Gradle wrapper.
If you need to use standalone Kotlin versions, installed for example through SDKMAN, consider taking the SDKMAN activation lines out of your shell init file (.bashrc for Bash) and into a standalone script (say, ~/bin/sdkman) that will also change your shell prompt (PS1 in Bash) to remind you that you have entered a SDKMAN-managed CLI session.

Using codenameone with lombok in Eclipse

I wonder if anyone is using codenameone with lombok in Eclipse. I've googled, but all I could find is an old question of mine.
A tiny success
I've tried it, took a demo project, modified nothing and opened it in my Eclipse configured for Lombok. When compiling, I got the same stacktrace as here. I've added
/usr/lib/jvm/java-8-oracle/lib/tools.jar
to the path under Preferences -> Installed JREs -> Edit -> JRE system libraries (which may be a pure non-sense) and it didn't help.
Then I've replaced compiler="modern" by compiler="extJavac" in build.xml and it compiles. I can even use Lombok annotations and they compile and work in the simulator.
The problem
I'm afraid, this was the simple part. I guess, for submitting, I need to replace the source code by the output of delombok. I've tried to submit it as is and nothing happened (no error, no response).
Has anyone done it already?
Any tips?

You shouldn't change the classpath but if the bytecode has access to the properties then it should "just work". If you look at the build.xml file you will notice that it has targets for every one of the supported platforms and before the target occurs you will see a compilation target that packages the JAR that's sent to the servers.
Steve wrote a post about porting other languages to Codename One. This is simple by comparison.

It actually works! All I had to do was to
add the path to lombok.jar to the Java Build Path1
in the javac call of the jar task
replace compiler="modern" by compiler="extJavac"
add the path to lombok.jar to the classpath
1 This is not recommended as the dependency is unavailable on the build server, but that's exactly right. Lombok is a compile-time only dependency and the build seems to be based on the dist.jar, where Lombok has already done its job.
One year later: There was a problem with my old setup, so I installed everything anew and it seems to work. Just note that there are three javac tasks in the build.xml.

Scala IDE Error -could not find/load main class

I am using Scala IDE 4.4.1.,using the jdk 8.When I try to run a scala program ,getting the error "Error: Could not find or load main class example.Credit" .

I was stuck with the same error a few days ago. In my case, it was an incompatibility of my JDK and the selected target JVM for my Scala project.
To check your current Java version, run java -version on the command line. To check your project JVM target in Eclipse, go to "Project > Properties > Scala Compiler" and check the target JVM (choose the same version as your current Java).
Hope it helps.

You should write object instead of class

I was having the same problem so that is how I came to this link & would like to share my findings. In my case I found that incompatible jars where present due to it was throwing error. After providing correct jar issue was resolved.

I used Scala for Eclipse IDE,
The solution for this could be right click on project and select scala -> Set the Scala Installation, will set the scala path to this project and rebuild the same.
Hope this helps you.

If the above mentioned solutions are already configured in your system and still getting this error then consider reading my answer. When incompatible scala jars are referenced by projects, a red cross mark is shown at project level and no errors are shown in scala files. In this situation scala code doesnt compile and when executed shows the message "error could not find or load main class scala". Best solution is to go to the scala installation folder and to check if the jar is present there, if present then reference it else reference jar files that do not show error (red mark) at project level or at source code.

Command works in terminal but not with java [duplicate]

What are the possible causes of a "java.lang.Error: Unresolved compilation problem"?
Additional information:
I have seen this after copying a set of updated JAR files from a build on top of the existing JARs and restarting the application. The JARs are built using a Maven build process.
I would expect to see LinkageErrors or ClassNotFound errors if interfaces changed. The above error hints at some lower level problem.
A clean rebuild and redeployment fixed the problem. Could this error indicate a corrupted JAR?

(rewritten 2015-07-28)
Summary: Eclipse had compiled some or all of the classes, and its compiler is more tolerant of errors.
Long explanation:
The default behavior of Eclipse when compiling code with errors in it, is to generate byte code throwing the exception you see, allowing the program to be run. This is possible as Eclipse uses its own built-in compiler, instead of javac from the JDK which Apache Maven uses, and which fails the compilation completely for errors. If you use Eclipse on a Maven project which you are also working with using the command line mvn command, this may happen.
The cure is to fix the errors and recompile, before running again.
The setting is marked with a red box in this screendump:

try to clean the eclipse project

you just try to clean maven by command
mvn clean
and after that following command
mvn eclipse:clean eclipse:eclipse
and rebuild your project....

Your compiled classes may need to be recompiled from the source with the new jars.
Try running "mvn clean" and then rebuild

The major part is correctly answered by Thorbjørn Ravn Andersen.
This answer tries to shed light on the remaining question: how could the class file with errors end up in the jar?
Each build (Maven & javac or Eclipse) signals in its specific way when it hits a compile error, and will refuse to create a Jar file from it (or at least prominently alert you). The most likely cause for silently getting class files with errors into a jar is by concurrent operation of Maven and Eclipse.
If you have Eclipse open while running a mvn build, you should disable Project > Build Automatically until mvn completes.
EDIT:
Let's try to split the riddle into three parts:
(1) What is the meaning of "java.lang.Error: Unresolved compilation
problem"
This has been explained by Thorbjørn Ravn Andersen. There is no doubt that Eclipse found an error at compile time.
(2) How can an eclipse-compiled class file end up in jar file created
by maven (assuming maven is not configured to used ecj for
compilation)?
This could happen either by invoking Maven with no or incomplete cleaning. Or, an automatic Eclipse build could react to changes in the filesystem (done by Maven) and re-compile a class, before Maven proceeds to collect class files into the jar (this is what I meant by "concurrent operation" in my original answer).
(3) How come there is a compile error, but mvn clean succeeds?
Again several possibilities: (a) compilers don't agree whether or not the source code is legal, or (b) Eclipse compiles with broken settings like incomplete classpath, wrong Java compliance etc. Either way a sequence of refresh and clean build in Eclipse should surface the problem.

I had this error when I used a launch configuration that had an invalid classpath. In my case, I had a project that initially used Maven and thus a launch configuration had a Maven classpath element in it. I had later changed the project to use Gradle and removed the Maven classpath from the project's classpath, but the launch configuration still used it. I got this error trying to run it. Cleaning and rebuilding the project did not resolve this error. Instead, edit the launch configuration, remove the project classpath element, then add the project back to the User Entries in the classpath.

I got this error multiple times and struggled to work out. Finally, I removed the run configuration and re-added the default entries. It worked beautifully.

Just try to include package name in eclipse in case if you forgot it
Import all packages before using it, EX: import java.util.Scanner before using Scanner class.
These improvements might work and it will not give Java: Unresolved compilation problem anymore.
Also make sure to check compiler compliance level and selected jdk version is same

As a weird case, I encountered such an exception where the exception message (unresolved compilation bla bla) was hardcoded inside of generated class' itself. Decompiling the class revealed this.

I had the same issue using the visual studio Code. The root cause was backup java file was left in the same directory.
Removed the backup java file
When the build failed, selected the Fix it, it cleaned up the cache and restarted the workSpace.