At least one class must have a static main() method

When running a JVM application manually with the java command, you'll need to specify the class that has the following static method:

    public static void main(String[] args) {
    }

This is the method that will be called by the java command after the JVM instance has finished initializing. It is comparable to C's and C++'s well-known main() entry point function. The string array args will contain the command-line parameters as passed by the operating system.

The preceding snippet illustrates Java code. Some JVM languages do not require the programmer to write this method manually; they automatically generate one when compiling the class. Also, some JVM frameworks automatically generate or provide this method.

There can be slight variations of the main() method, though:

• The name of the method's parameter is not important. The args is the convention. Sometimes argv is used, but something similar to arguments would also be fine.
• There can be variations of the argument type. A string array (in Java, String[]) is usually used, but a var args parameter (String..., covered in the next chapter) would work as well.

Here's an example of a valid main() function in Java with the string's var args parameter type and a different argument name:

    public static void main(String... commandLineArguments) { }

There can be more than one class with a static main() method in your project. But only one can run at a time. The fully qualified class name must be specified on the command-line when running the application with the java command.