what is the difference between main(String... s) and main(String[] s)?

Question

class Test{
    public static void main(String... s){
        System.out.println("Hello");
    }
}

class Test{
    public static void main(String[] s){
        System.out.println("Hello");
    }
}

What is the difference between above two syntax of main() declaration?

Does Java has any special need to have variable length argument?

Answer 1

No difference (when you run the program from the command line, i.e. what the main method is used for). The first variant appeared after Java 5 introduced varargs.

In short, varargs allows you to pass a variable number of arguments to a method. For the method body the arguments are grouped into an array. Like Test.main("foo", "bar") instead of Test.main(new String[] {"foo", "bar"}). The compiler does the array creation for you behind the scene.