import java.lang.Character;
import javax.swing.JOptionPane;

public class If
{
    // use if - else if - else to handle multiple alternatives
    public void ifExample()
        {String ageStr = JOptionPane.showInputDialog("How old are you?");
        int age = Integer.parseInt(ageStr);
        String msg;
        if (age >= 18)
        {
            msg = "You can get a full driver's license";
        }
        else if (age == 17)
            msg = "You can get a provisional license";
        else if (age == 16)
            msg = "You can get a learner's permit";
        else
            msg = "You can get a learner's permit when you're 16";
        JOptionPane.showMessageDialog(null, msg);   
    }
    
    public void compareNumbers()
    {   double r = Math.sqrt(2);
        double d = r * r - 2;
        // to compare 2 floating-point numbers, see if
        // their difference is less than some tolerance,
        // here, 1e-15.
        if (d < 1e-15)
            System.out.println("sqrt(2) squared minus 2 is 0");
        else
            System.out.println("sqrt(2) squared minus 2 is " + d);
    }
    
    // use .equals() to compare Strings and any objects
    // using compareTo() is also an option
    public void compareStrings()
    {   String n1 = "Irene"; String n2 = "Lingnan";
        String msg = "";
        if (n1.equals(n2))
            msg = "They match";
        else
            msg = "They DON'T match";
        //JOptionPane.showMessageDialog(null, msg);
        String n3 = "Josh", n4 = "josh";
        if (n3.equalsIgnoreCase(n4))
            msg = "They match";
        else
            msg = "They DON'T match";
        //JOptionPane.showMessageDialog(null, msg);
        int result = n3.compareTo(n4);
        JOptionPane.showMessageDialog(null, result);
    }
    
    public double taxReturn()
    {   final int SINGLE = 1;
        final int MARRIED = 2;
        final double RATE1 = 0.10;
        final double RATE2 = 0.25;
        final double RATE1_SINGLE_LIMIT = 32000;
        final double RATE1_MARRIED_LIMIT = 64000;
        double income;
        int status;
        String incomeStr, statusStr;
        incomeStr = JOptionPane.showInputDialog("Income? ");
        statusStr = JOptionPane.showInputDialog("Marital status?");
        income = Double.parseDouble(incomeStr);
        status = Integer.parseInt(statusStr);
        double tax1 = 0, tax2 = 0;
        
        // you can "nest" IF statements
        if (status == SINGLE)
        {  if (income <= RATE1_SINGLE_LIMIT)
              tax1 = RATE1 * income;
           else
           {
              tax1 = RATE1 * RATE1_SINGLE_LIMIT;
              tax2 = RATE2 * (income - RATE1_SINGLE_LIMIT);
           }
        }
        else if (status == MARRIED)
        {   if (income <= RATE1_MARRIED_LIMIT)
               tax1 = RATE1 * income;
            else
            {   tax1 = RATE1 * RATE1_MARRIED_LIMIT;
                tax2 = RATE2 * (income - RATE1_MARRIED_LIMIT);
            }
        }
        return tax1 + tax2;  
    }
    
    public void trueOrFalse()
    {   double amount = 0;
        System.out.println(amount < 1000);
        // return amount < 1000;
        // Some methods, like isDigit(), return a boolean:
        System.out.println(Character.isDigit('$'));
        System.out.println(Character.isDigit('3'));
        // Some expressions evaluate to a boolean:
        System.out.println(amount > -1000 && amount < 1000);
        System.out.println(amount < -100 || amount < 100);  
    }
           
    public static void main(String[] args)
    {   If i = new If();
        // i.ifExample();       
        //i.compareNumbers();
        //i.compareStrings();
        //double tax = i.taxReturn();   
        //String msg = "The tax is " + tax;
        //JOptionPane.showMessageDialog(null, msg);
        i.trueOrFalse();
       
    }
}