Q3. Classes More 1

We have NoisyDog and SportsFan classes to practice working with abstract classes and implementing interfaces.

NoisyDog

Write the abstract class Noisy and the subclass NoisyDog.

• The constructor should take in a number N that represents how many times it makes a noise. Remember the number N to use later.

• The noise() method will make the (unspecified) noise one time. It is abstract because the noise is not specified and there is no good “default”.

• The makeNoise() method repeats the noise() N times. This method is not abstract.

    public abstract class Noisy {
        // add any variables you need
        public Noisy (int n) { /* ... */ }
  
        // purpose: print the designated noise one time
        public abstract void noise();
  
        // print the designated noise N times
        public void makeNoise();
    }
  

The NoisyDog is a subclass of Noisy.

• NoisyDog(String barknoise) constructor causes the object to remember what noise it will make, and sets up the object to make the noise three times.

• The noise() method prints that noise.

• NoisyDog() constructor by default makes the noise “bark” and the number of times the noise is made 3.

    public class NoisyDog extends Noisy {
        public NoisyDog();
        public void noise();
        public NoisyDog(String barknoise);
    }
  

What would happen if you left out the noise() method?

SportsFan

The SportsFan interface is:

    public interface SportsFan {
        String cheer();
        String boo();
    }

1. Make a BoorFan class that implements the SportsFan interface. A BoorFan does not cheer, so just return the empty string for that method. A BoorFan returns "You stink!" when booing.

2. A DolphinFan says "flip" to cheer and "glub" to boo. Make the DolphinFan class.

3. Make a GetRowdy class that cheers twice, separated by spaces, when asked to cheer. It boos three times.

    public class GetRowdy implements SportsFan {
       // you might need instance variables
       public GetRowdy (SportsFan who) {
            // write this constructor
        }
        // other methods are required
    }
   

4. The following code has some OK parts and some errors. Which lines are errors? If a line is not an error, explain what happens when you call the cheer() method of that object.

    public void demo() {
        SportsFan s = new SportsFan();  // 1
        SportsFan t = new BoorFan();    // 2
        BoorFan b = new SportsFan();    // 3
        GetRowdy r = new GetRowdy();    // 4
        GetRowdy rr = new GetRowdy(t);  // 5
        GetRowdy d =
           new GetRowdy(new DolphinFan()); // 6
   
        /* Call cheer() on all of them. What do they do? */
    }