Did you run  the code as:

java ClassName

Or

java ClassName.class


The first form is the correct form. If you append .class it will not find your
class. Perhaps you can give some more
details if this is not the case. Stack traces, the command you used to execute
your code, etc. is always helpful.

Please tell me about
stack traces
my program  was runned by using visualcafe
i have not using .class extension.
as i have already gone through a number of
books and created a few program
which was running  fine previously

A stack trace occurs when you catch an exception and execute the
Exception's printStackTrace() method. A stack trace may also occur if a
RuntimeException is propagated all the way up to the VM.

In order to know more about your problem, can you post the command you
are issuing as well as the error which occurs.

What you are saying is right in my case.
My program  is now running

In one program I want to run  Dos Command
e.g. copy f1.jpg to f2.jpg
from the java  by process and runtime method
but it is not running  and
it shows error stack trace is disable

You can use command line commands from withing Java using the
Runtime.exec() method, but you should try to avoid it at all costs. The
main reason to avoid it is because it makes your application much less
portable. You should try instead to use the functionality in the Java
API or extend it to provide this functionality.

For example, if you want to copy one file  to another in Java you could
do something like:

FileInputStream in = new FileInputStream("filename1");
FileOutputStream out = new FileOutputStream("filename2");

int b = -1;
while((b = in.read()) != -1){
out.write(b);
}

out.close();
in.close();


You can do a lot to make this better though, such as buffering your
input and output data, checking to see if files exist before reading and
writing, catching exceptions, etc.