ClassNotFoundException vs NoClassDefFoundError

Question

I have gone through this thread What causes and what are the differences between NoClassDefFoundError and ClassNotFoundException? This is what one of the ans,which has max u

Answer 1

NoClassDefFoundError is usually called when you are using a library(for example, Guava, Gson, CommonsIO). You put the library in classpath of your project, but you didn't export it together, you will get a NoClassDefFoundError when the application is running.

How to get NoClassDefFoundError:
Create a new project, with this class.

public class A
{
    public void do()
    {
        System.out.println("Do!");
    }
}  

Export it as a .jarfile.

Now create another project. Add the exported jar file to classpath.

import ???.A;
public class Main
{
    public static void main(String[] args)
    {
        A a = new A();
        a.do();//NoClassDefFoundError thrown at here.
    }
} 

Export the project, make sure you do not include the jar file(with class A). Run the newly exported jar file, you will see that error!