Lesson Three
Boolean Logic, If and Else

Part Zero - Review

Write a program that calculates the number of pizzas to order for 16 people if each person will have 3 slices (0.375 pizzas) each. Try to write out the main method yourself but if you forgot just click here

public class Lesson3 {
    public static void main( String[] args ) {
        
        // your code goes here =)

    }
}
       

Your output should look like this:
Can I have ""number of pies"" to Hancock 0005?

Hint: use Math.ceil() to round up to the nearest whole pizza.

Part One - Boolean Logic, AND, OR and NOT

You should be fairly familiar with the following truth tables from high school. In java we have operators for each of these boolean expressions. We also have a type just for holding true and false values.
The type is boolean and the operators are:

Let's make a sample program to use boolean and our boolean operators...

boolean x = true;
boolean y = false;
boolean z = x || y;
System.out.println(z);
        

Part Two

Writing true and false aren't the only way to get boolean values. We can also compare ints doubles and Strings.

System.out.println( 2 == 2 ); // equals
System.out.println( 2 != 2 ); // not equal
System.out.println( 2 < 3 ); // less than
System.out.println( 3 > 2 ); // greater than
System.out.println( 2 <= 3 ); // less than or equal to
System.out.println( 3 >= 2 ); // greater than or equal to

String x = "yes";
System.out.println( x == "yes" ); //incorect way to compare strings
System.out.println( x.equals("yes") ); //correct way to compare strings
        

Part Three

The if is one of the most important controll structures in programming. It lets the computer make decisions based on a boolean statement.

boolean hasBrain = true;

if ( hasBrain ){
    System.out.println("would while away the hours conversin\' with the flowers");
}
	

Part Four

You can also provide something for the computer to do if it fails the test

String storedPassword = "password123";
String inputPassword = "password123";

if ( storedPassword.equals(inputPassword) ){

    System.out.println("You are logged in");

} else {

    System.out.println("Sorry incorrect poassword");

}
	

Part Four

If you need to test more than one condition use else if

double bodyTemperature = 98.6;

if ( bodyTemperature > 98.6 ){

    System.out.println("You have a fever");

} else if ( bodyTemperature < 98.6 ) {

    System.out.println("You have a cold");

} else {

    System.out.println("You are healthy");

}
	

Home Work

Make a program that tells you what score you got on a hole in golf. Use two variables, one for par and one for your score on the hole.
If your score is equal to par print : You got par!
If your score is one less than par print : You got a birdie!
If your score is one more than par print : You got a bogey!
Otherwise print : You got a ""your score""