Exception in thread "main" java.lang.NoClassDefFoundError: wrong name

Question

My file directory:

project/src/m2mcom/entities/AutomatedTelnetClient.java
           /web/Simple.java           
           /org/apache/commons/net/telnet/TelnetClient.java 

The source code of the Simple.java:

package m2mcom.web;
import m2mcom.entities.AutomatedTelnetClient;
import java.util.*;
import java.io.*;

public class Simple {
    public static void main(String [] args) {
        try {
            AutomatedTelnetClient telnet = new AutomatedTelnetClient();
            String answer = telnet.request();
            System.out.println(answer);
        } catch (Exception e) {
            System.err.println("Error");
        }
    }
}

And when I execute Simple.class, without any errors of compilation, I get this error message:

C:\Users\Victor\Desktop\project2\src\m2mcom\web>java Simple
Exception in thread "main" java.lang.NoClassDefFoundError: Simple (wrong name: m
2mcom/web/Simple)

Does anyone know how to solve this?

Answer 1

You're executing the command in the wrong folder, with the wrong classname. You need to use the fully qualified name (FQN) when running a Java class. And of course, you have to be in the right directory. In your example, the FQN of your class is m2mcom.web.Simple (combination of the package m2mcom.web and the simple name Simple).

As far as deducing the right directory, your classes are stored in a hierarchical folder structure, which basically starts in C:\Users\Victor\Desktop\project2\src.

So to correctly execute your program, from C:\Users\Victor\Desktop\project2\src, do;

java m2mcom.web.Simple