JAR:Exeption in thread "main" java.lang.NoClassDefFoundError

Question

Hello !
I desperatly tried for the last two month to Jar my files.
I used JBuilder and JCreator to build and run those programme.
And it works !
But when I trie to use the jar tools, the jar is created...but if I click twince on it, it says that it can not find the main function:
"Exeption in thread "main" java.lang.NoClassDefFoundError".
And when I try to run the .class or .java file, with the java tools, it says the same thing : it can not find the main classe.
I suspected that my manifest was not good, but then, why doesn't it work with the tools (and it works properly with Jbuilder!)...
I'm lost, if some one could help me, and give me good information and the way to do it, step by step, with an example, I'll be so thanksfull !
i.e.:
import java.*;
class Hello{
public Hello(){
public static void main(String args[]) {     
System.out.println("Hello World!");
}Thanks !
.Splitsch.

Answer 1

You have to tell where the main class is.
prepare a text file mainclass.txt and write the following line.
Main-Class: classname
follow the same as i wrote above. leave a blanl after colon and a blank line after the first line like above.
after that execute the command.
jar umf mainclass.txt jar-file-you-created
then run you jar file as
java -jar jar-file-you-crated
phani.