Static Error: This class does not have a static void main method accepting String[]

Since I want the user to enter numb开发者_如何学Goers instead of Strings I used

public static void main(Integer[] args)

So, why is this wrong?

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The signature on your main method MUST be:

public static void main(String[] args)

You don't have any other option. You may parse those strings as integers if you need to, via Integer.parseInt(someString)

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Main is special since it has to be present to start the program, so it's required to have a fixed signature. Under the hood, the java runtime looks for the magic signature to start the program. The magic signature is

public static void main(String[] args)

If you want to get Integers, you'll need to parse them out after the fact, using

Integer.parseInt( x );

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You can only have an array of String[] for your main method (unless you overload it, but let's not get into the details for now :-D).

However, you can change each element of the String[] args into an int by using Integer.parseInt, something like

public static void main(String[] args)
{
 int[] values = new int[args.length];
 for (String arg : args)
 {
  //Get or do something with the integer value here
 }
}

This is because the underlying platform only knows how to pass Strings to your program. When you open up a command prompt or terminal and do:

>java MyClass 3 4 5

It doesn't know that you want ["3","4","5"] treated like integers. It leaves dealing with the Strings up to the program.

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When the JVM loads your class and tries to execute it, it looks for the method main() with the signature

public static void main (String[] args) ...

Anything else is unaccptable. If you are expecting integers, use the Integer.parseInt() method to convert the input Strings to integers, as Zach mentioned. I'd put that conversion in a try-catch block to catch NumberFormatException, and have a

System.err.println ("This class accepts Integer arguments only"); 

in the corresponding catch block. Regards, - M.S.

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You'll need to accept a string array, and convert the strings to integers at runtime. Just the way it works...

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the method signature for main is always (String[] args). If you are going to get Integers, then you have to convert the args[] to int using the snippet below

  int aInt = Integer.parseInt(args[0]);