1. Now we know that we can declare classes that are abstract. What does it mean to be “abstract” and why would we want to do this?
2. On page 198, there is a picture of an inheritance hierarchy (tree). There are four methods defined in the Animal class: makeNoise(), eat(), sleep(), and roam(). But in some of the subclasses, these methods appear again! For example, there is a roam() in the Feline class and makeNoise() and eat() methods in the Wolf class. These common methods were supposed to be “abstracted” out into the superclass Animal. Why are they still in subclasses? Explain.
3. Let’s suppose that you have a class called “Restaurant” and it was defined below as:

   public class Restaurant
   {
   }

   Where would you add the word abstract to make this an abstract class?

4. OK, now let’s look at abstract methods. Suppose the abstract class
   Restaurant has a method called “cook()” as shown below:

   public void cook();

   Where would you add the word abstract to make this an abstract method?

5. True or False?
   a. There can be only ONE abstract class in an inheritance tree or hierarchy.
   b. You CAN have an abstract method in a non-abstract (concrete class) as long as you override it in a subclass.
   c. You CANNOT have non-abstract methods in an abstract class.
   d. You CAN use abstract class references as method arguments, return type, but NOT array types.
   e. Abstract methods MUST be overridden in subclass directly beneath it in the inheritance hierarchy.
   f. An ArrayList object is the “Mother” of all objects (all objects derive from ArrayList).
   g. To inherit the methods in type Object, you must explicitly state extends Object in your class declaration statement (for example: public class Tool extends Object).
   h. You CANNOT make an instance of type Object, since it is abstract.
6. What are the four methods that EVERY class has as a result of inheriting (explicitly or implicitly) from Object?
7. Can an abstract class can have a mix of both abstract and non-abstract methods?
8. On page 207 in this chapter, we were using the MyAnimalList class to store different types of a Animals. Why was it possible to store both Dogs and Cats in this class?
9. Creating an ArrayList of type Object can cause issues when you want to get objects from the ArrayList. For instance, let’s say you create an ArrayList of type Object called spaceThings:

   ArrayList<Object> spaceThings = new ArrayList<Object>();

   and then store instances of classes like Monster, Asteroid, and SpaceRanger in the ArrayList. There is a problem when you try to get the objects from the ArrayList. Describe problem that you can run into when you attempt to get objects from the ArrayList and use their respective methods.

10. There’s must be a way to fix the problem described above (without creating an ArrayList using a type more specific than Object). For example, assume we have an ArrayList called spaceThings as before:

    ArrayList<Object> spaceThings = new ArrayList<Object>();

    And let’s say that we have a Monster at index 0, an Asteroid at index 1, and a SpaceRanger at index 2. Write the three lines of code that you would use to correctly get these three elements from the ArrayList, and place them into a Monster variable m, an Asteroid variable a, and a SpaceRanger variable s. What is this process called?

11. Explain the differences between an abstract class and an interface.
12. Can a class extend a class and implement an interface?

Your presentation will be based on one of the incidents in the Joy Luck Club.  Since you have been writing Double Entry Journals for Ms. Peters, you should be able to look back at those notes and use them to help you select something from the book you found interesting.

In a 3-5 minute presentation, you will give an overview of your chosen moment from the book, and then tell your own story (either from your life or someone that you know very closely) and how it relates to the story in the book.  You will use PowerPoint to help you tell the stories, but remember that no one likes to watch someone read from the screen!  We want to hear you tell the story, and your slides are there to support and enhance what you’re saying — be sure they don’t detract or distract.

Final Presentation Rubric

Curve: All scores are automatically +10, which sets the top performers back into the A range.

Test Corrections: Everyone is eligible to write corrections to any missed problem.  Each problem will be considered individually.  Corrections are due Tuesday, 1/13/09 at 10:45am, the start of the APCS final exam period.  You may email or use paper. You may discuss problems with your fellow students, but each correction must be entirely your own writing and reflection your own understanding.

Credit: If your test corrections convince Mr. Chun that you understand the concept at hand, you will earn back half of the lost credit for that question.  The mathematically astute among you have noted that this allows someone who originally scored an 83 (for example) to reach a total of 93 + (17/2) = 101.5 and, perhaps more significantly, allows someone who originally scored a 20 to reach a total of 30 + (80/2) = 70.  Therefore, it is possible for everyone to earn a passing score on the test.

Some ways to convince Mr. Chun you understand a concept: Write out your thoughts and explain your ideas clearly. Be sure you are using vocabulary words correctly.  Give another example. Point out the way you previously misunderstood. Relate the solution to other concepts from the class. For multiple choice questions, identify the type of misunderstanding that would lead to some of the incorrect options offered.  A typical correction will consist of approximately one paragraph of explanation, along with any necessary code or diagrams.

Your character (specifically the frames of the walk cycle animation) should all be created inside a Movie Clip  symbol called “walk”.  Remember that symbols are created and managed in the Library.  This character will eventually do more than just walk, but for now you just need one symbol.

A lot of information about the personality and style of your character is conveyed through how it walks.  This tutorial is a good starting point.  The following drawings from Preston Blair also give a sense of the keyframes.

Due to be shown to the class for critique during the Final Exam period Thursday 1/15/09,  10:45am – 12:45pm.

In this lab, you will be extending the following base class:

public class Pet
{
  private String name;
  private int weight;

  void setName( String n )
  {
    name = n;
  }
  String getName()
  {
    return name;
  }
  void setWeight( int w )
  {
    weight = w;
  }
  int getWeight()
  {
    return weight;
  }
}

Your job is to create three subclasses of Pet, each in their own .java file of course, using the extends syntax. Each subclass should have at least one private member variable that represents a property unique to that subclass. In addition to all necessary setter and getter methods, each subclass should should at least one method that represents a behavior or activity unique to that subclass.

Once you’ve created your three subclasses, create a PetTestDrive class to demonstrate them. Create at least one instance of each Pet-derived class, and call its unique methods. Put all the instances into an ArrayList that can hold only Pets. Then write a loop that will display the name and weight of each Pet.

Topics: This is a comprehensive test covering all topics this semester, through Chapter 6 and Lab 8.5. This includes, but is not limited to: the compiler, source code/object files, syntax vs. semantics, classes, naming conventions, method and variable declarations, types (primitive vs. reference), String methods, loops, conditionals, arrays, and encapsulation.

Format: There will be various question types, including multiple choice, fill-in items, writing short sections of code, and free response.

1. What is the process of moving common elements (methods and variables) to another class? What is the name of this special new class?

2. Once a superclass is created, what main purpose does it serve?

3. In page 167, it looks like there are rotate() and playSound() methods in both the Shape and Amoeba classes. Shouldn’t the Amoeba rotate() and playSound() methods be put into the Shape class? Why does the Amoeba class have its own versions of rotate() and playSound()?

4. When you have a method in both a superclass and a subclass, how does the JVM know which one of these to call?

5. In the inheritance tree on page 168, there is a FriedEggMan who inherits from a SuperHero superclass. FriedEggMan does not override any of the superclass methods, so what makes a FriedEggMan unique? Does he inherit anything else?

6. How can a programmer determine which methods should be overriden?

7. Can a class have a superclass and a subclass?

8. The book keeps talking about how polymorphism can “make my life easier.” Give two examples of how polymorphism allows programmers to program more efficiently.

9. What is the difference between overriding a method and overloading it? Give an example of each situation (this should be Java code as well as your explanation of it).

You might find this FAQ about inheritance useful.

• Pick one of the following classes you created in a previous lab: Student or Clock.
• Create a new class called ArrayLister. (Note the -er ending on that class name.)
• The following instructions all refer to the main method of ArrayLister:

1. Create an ArrayList called myList that can hold objects of your chosen type (Student or Clock).
2. Write code that will pick a random number x between 5 and 10.
3. Create a loop that will construct exactly x Student or Clock objects and store them in myList.
4. Once this is done, set some value for each Student or Clock object by calling a method such as setName or setHours. (You have different options for accomplishing this goal, not just in your choice of method to call, but also in how you access each of the items in myList. Don’t forget about the API reference!)
5. Finally, call a method on each Student or Clock that will print some output (for example: the time or the name and GPA.)