HelloWorld can be complied but can't run:NoClassDefFoundError

Question

so simple programe but I can't figure out, I hate myself.
package com.aplha.simple;
public class HelloWorld
     public static void main(String[] args) {
          System.out.println("hello world");
}HelloWolrd.java and HelloWorld.class in the same directory:com\alpha\simple exactly same with the package hierarchy. HelloWorld.java can be compiled to HelloWorld.class, but everytime when I use java command to run the program I receive the following error message:
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong nam
e: com/aplha/simple/HelloWorld)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:12
4)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)I have configured current directory(.) into the CLASSPATH environment variable and My environment is
OS: XP SP3
JDK: 1.6.0_06
Can anyone tell me the reason why I can't launch the program, any help is appreciated !

Answer 1

laianfa_alpha wrote:
my directory structure:
E:\test\src\com\alpha\simple
now I am in simple directory I type : java com.alpha.simple.HelloWorld, still the error message
Exception in thread "main" java.lang.NoClassDefFoundError: com/alpha/sim
oWorld
Caused by: java.lang.ClassNotFoundException: com.alpha.simple.HelloWorld
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
In my previous reply post, I didn't mean to guess what directory structure you actually had, but was providing you with an example for you to adapt to; point being that you must be up the directory stream to run it ... have a reread of my post and it will become clear.