Why am I getting a NoClassDefFoundError in Java?

A NoClassDefFoundError in Java indicates that the Java Virtual Machine (JVM) or a ClassLoader was not able to find the definition of a class that was referenced in your code. This can occur for a variety of reasons, including:

• The class was not included on the classpath when the JVM was started.
• The class was present on the classpath when the JVM was started, but it was subsequently removed or modified.
• The class is a part of a library or a plugin, and the library or plugin is not installed or not available.

To troubleshoot a NoClassDefFoundError, you should first check that the class is present on the classpath. If the class is present and the error persists, you should check that the class was not modified or deleted after the JVM was started.

If the class is a part of a library or a plugin, you should check that the library or plugin is installed and available to the JVM. You should also make sure that any dependencies of the library or plugin are also installed and available.

If you are unable to resolve the NoClassDefFoundError, you may need to provide more information about your code, the classpath, and the environment in which the error is occurring.