import javax.swing.*;

public class Postage {

    public static void main(String[] args) {

        runTests();

        String input = JOptionPane.showInputDialog("Weight:");
        double weight = Double.parseDouble(input);

        String output = getPostage(weight);

        JOptionPane.showMessageDialog(null, output);
    }

    private static String getPostage(double weight) {
        String output;
        if (weight <= 0.0) {
            output = "Weight must be positive!";
        } else if (weight <= 20.0) {
            output = "Postage is 5.50 kronor.";
        } else if (weight <= 100.0) {
            output = "Postage is 11.00 kronor.";
        } else if (weight <= 250.0) {
            output = "Postage is 22.00 kronor.";
        } else if (weight <= 500.0) {
            output = "Postage is 33.00 kronor.";
        } else {
            output = "Too heavy: use a packet.";
        }
        return output;
    }

    public static void runTests() {
        testPostage(10.0, "Postage is 5.50 kronor.");
        testPostage(20.0, "Postage is 5.50 kronor.");
        testPostage(20.5, "Postage is 11.00 kronor.");
        testPostage(150, "Postage is 22.00 kronor.");
        testPostage(300, "Postage is 33.00 kronor.");
        testPostage(-10, "Weight must be positive!");
        testPostage(Double.MAX_VALUE, "Too heavy: use a packet.");
        testPostage(Double.POSITIVE_INFINITY, "Too heavy: use a packet.");

        for (int i = 0; i < 100; i++) {
            double weight = Math.random() * 1000;
            String output = getPostage(weight);
            System.out.print(". ");
        }
    }

    private static void testPostage(double weight, String expected) {

        String actual = getPostage(weight);

        if (expected.equals(actual)) {
          System.out.print(". ");
        } else {
            System.out.println("Test failed!");
            System.out.println("Input: " + weight);
            System.out.println("Expected output:" + expected);
            System.out.println("Actual output:" + actual);
        }


    }

}