Problem 1 was a Code Warrior exercise.

Solutions for problems 2 to 4:

2. [5 pts] Do exercise 3, p. 111.

    Ans:
    a)BorderLayout/Flowlayout -  No subclass<->superclass  relationship.
    b)TextArea/TextComponent -  TextArea is a subclass of TextComponent
    c)TextField/Component  -  TextField is a subclass of Component
    d)Button/Component  -  Button is a subclass of Component
    e)Panel/Object  -  Panel is a subclass of Object

3. [5 pts] Describe the relationship we want among subclasses.  For example, how do we know something should be a subclass of another class?

    Ans:
    To determine if a class A should be a subclass of another class B, we look for an "is-a" relationship between the two. ie, we see if the statement A is-a B makes sense. If it does, then we make A a subclass of B.

4. [5 pts] Why is encapsulation and information hiding important for programs?  How can we achieve these in Java?

    Ans:
    Encapsulation is important because when it comes to large projects, it is easier to develop the components of the project and then "plug" them together. So we should be able to "trust" the components to exhibit the behavior we expect of them(or in other words, we expect them to perform their "roles" perfectly). This is achieved by splitting up the responsibilities between the different easily manageable classes and encapsulating it.

    An object can be accessed or its state altered only through the public methods - everything else is "hidden" from the "outside world". This is the concept of Information Hiding. The idea behind it is that you do not really need to know how a class implements a method when you pass a message to an object of that class. You can "trust" it to behave correctly.