Develop Reference

java.lang.NoClassDefFoundError when running via Eclipse

I get the following error messages when attempting to run my program via Eclipse:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang3/JavaVersion
at lemmini.LemminiFrame.main(LemminiFrame.java:762)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang3.JavaVersion
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:606)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:168)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
... 1 more
The project has all necessary dependencies loaded and there are now 0 errors in the code (there are some warnings though).
Ideas welcome. Thank you!

OK, it turns out that the issues I've been experiencing are all to do with the dependencies. I loaded them into a folder called 'dependencies' within the project folders (alongside 'src') and then imported them from there via Project>Properties>Java Build Path>Libraries (then choose Classpath>Add JARs)
I can now run the program within Eclipse, but can't run it as an executable .jar
The journey continues...

Build Problem with AnysoftKeyboard (Android)

I am trying to build AnysoftKeyboard in Android studio.
I have java 9(jdk 9) and the appropriate ndk (android-ndk-r14b), as the creator in GitHub says.
I have also changed the local.properties file to shows to the correct paths.
Nevertheless I am still getting some errors.
You can find below those errors.
Run tasks error :
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':base:compileDebugJavaWithJavac
java compiler errors : Caused by: java.lang.BootstrapMethodError: java.lang.NoClassDefFoundError: com/sun/tools/javac/util/JavacMessages$ResourceBundleHelper
Caused by: java.lang.NoClassDefFoundError: com/sun/tools/javac/util/JavacMessages$ResourceBundleHelper
Caused by: java.lang.ClassNotFoundException: com.sun.tools.javac.util.JavacMessages$ResourceBundleHelper
Here is a screenshot of the error :
AnySoftKeyboard Compile Error , Run Tasks Error
The project uses gradle, in which I am not familiar with, so if I have missed any important step-point, please guide me to solve it.
Is there something that I am missing and getting these errors? What should I do? Thanks in advance.

After following just the official documentation I successfully built a project. I think you just forget with setting JAVA_OPTS with adding java.se.* source as mentioned below. And that is why you have it in stacktrace error above, with missing java.se. resources.
To develop this project, you'll need:
Java 10 - get OpenJDK or AdoptOpenJDK.
Make sure you have the environment variable JAVA_OPTS='-XX:+IgnoreUnrecognizedVMOptions --add-modules java.se.ee'. This is required to ensure the JVM is merciful with libraries that were not designed for Java9+ JVMs.
git
Android Studio
Android SDK API Level 28 installed. Set up local.properties file to point to it (that is, ensure you have sdk.dir=/path/to/android/sdk in it).
Android NDK r14b installed. Set up local.properties file to point to it (that is, ensure you have ndk.dir=/path/to/android/ndk in it).

Caused by: java.lang.BootstrapMethodError: java.lang.NoClassDefFoundError: com/sun/tools/javac/util/JavacMessages$ResourceBundleHelper
TO remove this error comment below line prone error.

Exception in thread "main" org.apache.velocity.exception.VelocityException

Does anyone know how can I solve this problem?
I am trying to make a connection with amazonMechanicalTurk using Java API.
Exception in thread "main"
org.apache.velocity.exception.VelocityException: Error initializing
log: org.apache.log4j.Logger object set as runtime.log.logsystem is
not a valid log implementation.
Caused by: org.apache.velocity.exception.VelocityException:
org.apache.log4j.Logger object set as runtime.log.logsystem is not a
valid log implementation.

Do yourself a favor, working with Velocity I've learned that is better to shut down his damn log:
//disabling Velocity log
Velocity.setProperty("runtime.log.logsystem.class", "org.apache.velocity.runtime.log.NullLogSystem");

I just decided to add some other Velocity libraries to my project.
My project only had the Apache Velocity jar file, then from here, I also added Velocity-Dep to my Maven project and Yesssssssssss! VICTORY!
Still asking why?!! because my project was working well until I decided to update java-aws-mturk library to version 1.7.0; then after I got that error!

JAssimp - Can't find dependent libraries

I've compiled the JAssimp library, and I'm trying to use the library in NetBeans with a project.
I'm setting the library path in Netbeans in the 'run' options of the project as such:
-Djava.library.path=D:\VB2013Projects\jassimpfinal\x64\Debug
That path is where jassimp.dll is located.
However, when I try to run my project, I get this error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: D:\VB2013Projects\jassimpfinal\x64\Debug\jassimp.dll: Can't find dependent libraries
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1929)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1847)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1119)
at jassimp.Jassimp.<clinit>(Unknown Source)
at opengltutorials.Mesh.loadMesh(Mesh.java:131)
at opengltutorials.Tutorial.init(Tutorial.java:124)
at opengltutorials.Tutorial.main(Tutorial.java:238)
I've checked the dependencies with Dependency Walker, and it shows that
Error: At least one module has an unresolved import due to a missing export function in an implicitly dependent module. for jassimp.dll. However, it doesn't show any functions in red, so I think this is just a red herring (I am probably wrong, though).
What's going wrong with this?

Fixed this by putting the appropriate .dll's in the working directory.

Class in buildpath-jar still not found

I'm developing a eclipse plugin rcp and I'm running into a NoClassDefFoundError
Exception in thread "Thread-7" java.lang.NoClassDefFoundError: org/jdom/input/SAXBuilder
at org.geonames.WebService.search(WebService.java:783)
at geo.GeocoderGeonames$SearchThread.run(GeocoderGeonames.java:119)
Caused by: java.lang.ClassNotFoundException: org.jdom.input.SAXBuilder
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClassInternal(BundleLoader.java:483)
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:399)
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:387)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:87)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
... 2 more
The class that supposedly cannot be found is in a jar that I have added to the buildpath. I don't get any compile error etc only this exception when the running application enters the code where this class is needed...
Is there some other place I need to add the jar

After reading this added the jar to the MANIFEST.MF, which solved the problem.
As I understand it, eclipse starts several classloaders which only sees what MANIFEST.MF tells them to see and ingnores the build path...

How are you running your plug-in? You may need to add the JAR to the class path in the VM arguments.

In our experience a NoClassDefFoundError can sometimes mean that more than one version of a Class are found, as there is also a ClassNotFoundException that's normally thrown if a class cannot be found.
Another reason in your case (XML parser) might be something with endorsed classes. Are you directly importing the jdom classes or something like org.w3c...? If so, have a look at the "endorsed classes" system of Java, something that I just recently came across.