Exception in thread main java.lang.NoClassDefFoundError: package javaClass

File : JavaClass.javaLanguage : Java
package javaexamples;

import java.util.ArrayList;

public class JavaClass {

	public static void main(String[] args) {

		final ArrayList arrList = new ArrayList();
		
		String s1 = "Java";
		String s2 = "PHP";
		String s3 = "Ajax";
		String s4 = "XML";
		
		arrList.add(s1);
		arrList.add(s2);
		arrList.add(s3);
		arrList.add(s4);
		
		System.out.println("Contents : " + arrList);
	}
}

Exception in thread "main" java.lang.NoClassDefFoundError: javaexamples/JavaClass
Caused by: java.lang.ClassNotFoundException: threads.Sample
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

NoClassDefFoundError is an exception thrown by the JVM: Java Virtual Machine class Loader Subsystem instance is unable to locate the class file definition. If you are using Eclipse IDE you may see that no error is being displayed on the Class file yet when you try to run the class you get NoClassDefFoundError, this is because the class file was available at compile time but not at runtime.

If you are working on Eclipse IDE, then check if there is any error displayed on your project folder under package explorer

If you are running the java from Windows Command Prompt, then you have to check that the classpath environment variable is set correctly.