How to Run HelloWorld program?

Hi,

I just write my first java program HelloWorldApp.java

But when i run it, im getting error like this....

C:\Java\jb\Ch04>java HelloWorldApp
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorldApp (wrong
name: jb/ch04/HelloWorldApp)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknow n Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: HelloWorldApp. Program will exit.

I set my CLASSPATH.
set CLASSPATH=.;C:\Java;C:\Java\lib

But still im getting the same error. Can anybody help, Please...

may you add some of your coding ?

Did you compile the file into a .class file first?
What package is the class in? Did you create a package structure that matches the package name? After doing all this, you then provide the path to the .class file with the -cp flag to the java command.

This is my HelloWorldApp.java

package jb.ch04;
import java.lang.System;
class HelloWorldApp{
public static void main(String args[]){
System.out.println("Hello World!");
}
}

I created directories jb\ch04 under java dir and saved the above file.

In the command prompt I did

C:\Java\jb\Ch04>javac HelloWorldApp.java

C:\Java\jb\Ch04>java HelloWorldApp
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorldApp (wrong
name: jb/ch04/HelloWorldApp)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknow n Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: HelloWorldApp. Program will exit.



I set Classpath firstly as
.; C:\Java\lib

and secondly as
C:\Java\jre\bin

Still Im getting the same error....

What name does your class have? It should be the same as the filename. For example, if your filename is HelloWorldApp.java, your class should be called public class HelloWorldApp (java is case sensitive!).

The both (filename and classname) are same..

now its working...
I have no idea how this happens.

I think the classpath must be c:\Java\jre\bin.

Thank you everyone.

No. The classpath must point to your class files not the jre bin.

Quote:

---

Originally Posted by siji44

Hi,

I just write my first java program HelloWorldApp.java

But when i run it, im getting error like this....

C:\Java\jb\Ch04>java HelloWorldApp
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorldApp (wrong
name: jb/ch04/HelloWorldApp)

---

I think for now it's better not to store your class in any package (except the default package). First study about the classpath variable and what packages actually imply. First remove that "package jb.cho4;" statement from your source code and try again.

kind regards,

Jos