Answer to Monday’s Question

This week’s question centered around this code:

// A jolly message is written to the screen!
class Jollymessage
{

   public static void main(String[] args) {

     //Write the message to the terminal window
     System.out.println("Ho Ho Ho!");

   }
}

that had been saved in a file called JollyMessage.java.

As I see from Monday's comments, the eagle-eyed of you quickly noticed that the class is called “Jollymessage” whereas the filename is “JollyMessage.java”.

For those that didn't see the error, remember that Java is case sensitive. The compiler won’t complain because technically there is nothing wrong with the code. It will create a class file that matches the class name exactly i.e. Jollymessage.class. So, when you come to run the program called JollyMessage, you can't because there is no file called JollyMessage.class.

The error you get when you try and run a program with the wrong name is:

Exception in thread “main” java.lang.NoClassDefFoundError: JollyMessage (wrong name: JollyMessage)..

Happily it’s a simple fix, just change the class name so that it matches the file name (or vice versa).