Java: Check if command line arguments are null

Question

I am looking to do some error checking for my command line arguments

public static void main(String[] args)
{
    if(args[0] == null)
    {
        System.out.println("Proper Usage is: java program filename");
        System.exit(0);
    }
}

However, this returns an array out of bounds exception, which makes sense. I am just looking for the proper usage.

Answer 1

The arguments can never be null. They just wont exist.

In other words, what you need to do is check the length of your arguments.

public static void main(String[] args)
{
    // Check how many arguments were passed in
    if(args.length == 0)
    {
        System.out.println("Proper Usage is: java program filename");
        System.exit(0);
    }
}