public class SquareTool {
    public SquareTool(String input) {
        try {
            float in = Float.parseFloat(input);
            Square sq = new Square(in);
            float result = sq.value;
           System.out.println("The square of " + input + " is " + result);
        } catch (NumberFormatException nfe) {
            System.out.println(input + " is not a valid number.");
        }
    }

    class Square {
        float value;

        Square(float x) {
            value = x * x;
        }
    }

    public static void main(String[] arguments) {
        if (arguments.length < 1) {
            System.out.println("Usage: java SquareTool number");
        } else {
            SquareTool dr = new SquareTool(arguments[0]);
        }
    }
}