The error message says it all. The showInputDialog method returns a string so you cannot assign it to an integer datatype. What you would need to do is convert it to an integer first.
public class ito
public static void main(String args)
String input = JOptionPane.showInputDialog("Enter number: ");
int number = Integer.parseInt(input);
System.out.println("you typed zero");
System.out.println("you typed one");
System.out.println("you didn't type zero or one");
Of course it would probably be a good idea to add in some code to validate the input to ensure it actually is a number that they entered and also the required number of digits.