import javax.swing.JOptionPane;

public class Ch5
{
    double balance = -100;
    // predicate methods return a boolean value
    public void predicateMethods()
    {   char ch = 'f';
        if (Character.isLowerCase(ch))
            System.out.println(ch + " is lowercase.");
        if (Character.isLetter(ch))
            System.out.println(ch + " is a letter.");
    }
    
    // predicate method:
    public boolean isOverdrawn()
    {   return balance < 0;        
    }
    
    public void booleanExpressions()
    {   double amount = 100;
        double cash = 200;
        System.out.println(amount > 0);
        System.out.println(2 > 3);
        boolean married = false;
        System.out.println(married == true);
        System.out.println(amount > 0 && cash > 500); 
        System.out.println(amount > 0 || cash > 500);
        String ltr = "A";
        System.out.println(ltr.equals("B"));
        System.out.println( ! ltr.equals("B"));
        String msg = "\nWe expect:\ntrue\nfalse\nfalse\nfalse\ntrue\nfalse\ntrue\n";
        System.out.println(msg);
    }
    
    public void nestedIF()
    {   // simplified tax calculator
        boolean married = false;
        double income = 75000, tax;
        if (income >= 200000)
            if (married) // same as if (married == true)
                tax = 0.25 * income;
            else
                tax = 0.2 * income;
        else if (income >= 100000)
            if (married)
                tax = 0.2 * income;
            else
                tax = 0.18 * income;
        else if (income >= 50000)
            if (married)
                tax = 0.15 * income;
            else
                tax = 0.12 * income;
        else
            if (married)
                tax = 0.1 * income;
            else
                tax = 0.08 * income;
        String msg = "Your income is $" + income;
        msg += " and you are married: " + married;
        msg += " and your tax is $" + tax;
        JOptionPane.showMessageDialog(null, msg);
        
    }
    public void ifStatement()
    {   int age = 91;
        String msg = "";
        if (age < 16)
            msg = "You'll have to wait.";
        else if (age == 16)
            msg = "You can get a learner's permit.";
        else if (age == 17)
            msg = "You can get a provisional license.";
        else if (age >= 18 && age <= 90)
            msg = "You can get a full driver's license.";
        else
            msg = "You probably shouldn't be driving.";
        System.out.println(msg);      
    }
    public void compareNumbers()
    {   double r = Math.sqrt(2);
        double d = r * r - 2;
        System.out.println("d: " + d);
        //if (d == 0)
        if (Math.abs(d) < 1.0E-15)
            System.out.println("you get 0");
        else
            System.out.println("you don't get 0");        
    }
    public void compareStrings()
    {   String name1 = "Patrick";
        String name2 = "Luka";
        String name3 = "Luka";
        if (name1.equals(name2))
            System.out.println("They're the same.");
        else if (! name1.equals(name2))
            System.out.println("They're different.");
        // OR
        int result = name1.compareTo(name2);
        System.out.println("result: " + result);
        result = name2.compareTo(name3);
        System.out.println("result: " + result);       
    }
    public static void main(String[] args)
    {   Ch5 c = new Ch5();
        //c.ifStatement();
        //c.compareNumbers();
        //c.compareStrings();     
        //c.nestedIF();
        //c.predicateMethods();
        //System.out.println(c.isOverdrawn());
        c.booleanExpressions();
    
    }
}