AP Computer Science --- Haas --- if else

Below are 4 example of the if - else structure. Copy each to BlueJ and run.

/** >>>>>>>>>>> Basic if - else statement <<<<<<<<<<<<
 * Below is a the basic if-else statement which
 * you should already be familiar with.
 * Copy it into BlueJ and run it. Make sure you
 * understand how it works.
 */ 

class TestIf {
    public static void main(String[] args) {
    
        int x = 12;
        int y = 10;
        
        if( x == y ) {
            System.out.println(x + " equals " + y);
        } else if( x > y ) {
            System.out.println(x + " is greater than " + y);
        } else {
            System.out.println(x + " is less than " + y);
        }
    }
}

/** >>>>>>>>>>> if - else with Strings <<<<<<<<<<<<
 * Below is an if - else statement which prints two 
 * strings in Alphabetical order, using the compareTo method.
 *
 * Copy to BlueJ and run, make sure you understand it.
 */ 
class StringIf {
    public static void main(String[] args) {
    
        String pet1 = "cat";
        String pet2 = "dog";
        
        if( pet1.compareTo(pet2) < 0) {
            System.out.println(pet1 + " is before " + pet2);
        } 
        else if( pet1.compareTo(pet2) > 0) {
            System.out.println(pet2 + " is before " + pet1);
        }        
        else {
            System.out.println(pet1 + " equals " + pet2);
        }
    }
}

/** >>>>>>>>>>> if - else with null Strings <<<<<<<<<<<<
 * Below is an example of using null with if statements.
 * When you set something to null it refers to NO object.
 * 
 * Copy to BlueJ and run, make sure you understand it.
 */ 
class nullExample {
    public static void main(String[] args) {
    
        String name = "Haas";
        String car = "Toyota Rav4"; 
        String boat = null;
        
        if(name != null) {
            System.out.println("Hello  "  + name);
        } 
        
        if(car != null) {
            System.out.println("Car = " + car);
        }        
        else {
            System.out.println("You do not own a car.");
        }

        if(boat != null) {
            System.out.println("Boat = " + boat);
        }        
        else {
            System.out.println("You do not own a boat.");
        }
    
    }
}

/** >>>>>>>>>>> BOOLEAN if - else <<<<<<<<<<<<
 *  Below are 10 example using boolean valiables
 *  with if statements.
 *  
 *  Read it over carefully.  Try to decide what the output
 *  will be before you run it.
 *   
 * Copy to BlueJ and run, make sure you understand it.
 */ 
public class BooleanIf
{
  public static void main (String args[]) {
    boolean a = true;
    boolean b = false;

    if (a) { System.out.println ("Example 1"); }
    
    if (b) { System.out.println ("Example 2"); }
    
    if (a && b) { System.out.println ("Example 3"); }

    if (a || b) { System.out.println ("Example 4");  }
    
    if (a == b) { System.out.println ("Example 5"); }

    if (a != b) { System.out.println ("Example 6"); }

    // the following are examples of DeMorgans law
    if (!(a && b)) { System.out.println ("Example 7"); }
    
    if (!(a || b)) { System.out.println ("Example 8"); }

    if (!a && !b) { System.out.println ("Example 9"); }
    
    if (!a || !b) { System.out.println ("Example 10"); }
    
    
  }
}