Possible Solutions for the Midterm Examination
		Computer Science 345

1.  This program is basically an expanded version of a program that was 
a sample in class late last week.  There is one tricky part:  the class
lettuce does not have an explicit constructor.  Instead a method Cheese
( ) is defined in that class, but never used.  Otherwise, the question is
just a careful application of the initialization rules presented in class,
and explained in the textbook.
	Here is the output:
	Meal
			The TIme default constructor would be called next,
			but it probably does not produce any output.
	Lunch
	PortableLunch
	GrainFood
	Bread		These last two for the top variable contained in
			Sandwich
	GrainFood
	Bread		These last two for the bottom variable 
	DairlyFood
	Cheese		For the c variable
	Sandwich

2.  There are many needed changes.  These include the need to import java.
applet.Applet, and java.awt.*, the need to extend the Applet class in 
the main class, the need to use an init ( ), and a paint ( Graphics g)
method, the removal of the main method ( not actually necessary, but it
is never used by the applet), and the replacement of all calls to 
println with uses of the drawString method of the Graphics object, g.

3.  I will use indentation to place derived classes under their base
class.
	Meal
		Lunch
			PortableLunch
				Sandwich
	GrainFood
		Bread
	DairyFood
		Cheese
	Lettuce
Meal, GrainFood, DairyFood and Lettuce could be placed under Object from 
which they all inherit implicitly, if you wish.

4.  Lettuce ( String k)  {
	kind = k;  }
Then change the use of Lettuce in main to new Lettuce("Romaine")

5.  Add this line to the Sandwich class:	Meal m
Then add these lines within the main method of the Sandwich class:
	m = new Meal ( );
	m = new Lunch ( );
	m = new PortableLunch ( );
	m = new Sandwich ( ) ;
This is an example of upcasting.

6.  Class variables are indicated by the modifier Static.  Just place 
Static in front of each variable declaration.

7.  Constants are indicated by the final modifier.  Just place final in 
front of each variable declaration.  Then after the variable name put 
new Class-name ( )

8.  	Meal [ ] [ ] meals = { { new Sandwich(), new Lunch( ) },
			{ new PortableLunch ( ), new Sandwich( ) }};
Each element in the array must be assigned a new object of the Meal class
or of one of the classes that can be upcasted to Meal.  

9.  Each of the classes in this program contains executable code.  Thus
none of the classes can be an interface.

10.  Add to the Lettuce class something like:
	public void lettuceType ( )  {
		System.out.println (kind);
		}
Then add a line to the main method
	l.lettuceType( );

11.  Notice that only the erase method is ever called.  The output 
is:
	Triangle erase
	Square erase
	Circle erase
	Square erase
This is an example of polymorphism.  It uses a slightly modified version
of a sample program explained in class and in the textbook.

12.  An abstract class cannot itself have any objects.  Shape and perhaps
Shapes are the only classes that do not have objects.