How to compile and run a java program?

Question

I am getting this error message, what to do?
Exception in thread "main" java.lang.NoClassDefFoundError:
Thanks for you help.
Ajay

Answer 1

Hello,
I believe that this error is caused because when you
compile and run a java program, you have to use the
same name that is next to public class. For example,
the program name is next to the word public class.
For example, if a program began like this:
public class Concat
then the name of the program in this case is Concat
and when you compile it you type: javac Concat.java
when you run it type: java Concat
depending on the name of your program.and depending on whether the class is in a package. And depending on what directory you are currently in.
Also depending on if you set your class path you might
have to type the above like this: jdk1.2.1\bin\javac
Concat.java to compile, and to run you would have to
type jdk1.2.1\bin\java Concat where you would replace
Concat with the name of your program and replace
jdk1.2.1 with the name of your version of java, that
is again if you do not have your classpath set. Hope
this helps.Your examples have nothing to do with whether the CLASSPATH is set--only with whether the PATH is set. And, it may not be jdkXXX\bin. The path to the JDK (in this case, to javac and java executables) could be anything. Classpath should be set on the command line. The OP probably did NOT set a classpath on the command line (preferred), or in the environment variables.
Also, make sure you did not forget to put:
public static void main(String[ ] args)
on the line underneath the line where it says "public
class Concat" where Concat is the name of your
program. Again, I hope this helps.Irrelevant (with the info we have from the OP so far). The error says that the JVM can't even find the class--not that the class doesn't have a main. The "main" referred to in the error message is within the JVM itself.
OP: Did you fix your problem? If not, what directory are your files in? Are they in a package? What command are you typing to get that error? That is, please tell us your entire command line.