java - 如何理解用户输入的类型

Question

我试图了解用户输入的类型是数字、字符还是字符串。我怎样才能完成评论中想要的任务？

public static void main(String[] args) {
        Calculator calculator=null; 
        Scanner num = new Scanner(System.in);
        System.out.println("press C to clear.  press E to terminate. ");
        while (true) {
                String input = num.nextLine();
                UserInputHandler.handleuserinput(input, calculator);
// if the input is a number do some thing.
//if the input is a character do some thing else.
   }
}