CSE 341 - Assignment 9 - Java Generics

Due: Dec 8, 10pm. You can use 1 late day for this assignment. (The reason for this is so that we can post a sample solution for people who want to use it to study for the final.)

8 points total

Turnin: You should turn in three files: ArrayExample.java, GoodArrayExample.java, and ArrayListExample.java

These questions use a hierarchy of classes of simple geometric objects. Here are the definitions:

Test.java is a little test class that you can run to make sure the other classes are working. For convenience, here is a zip file containing all the definitions, as well as the skeleton code for the Java questions: geometric.zip.

Running Java: You can run Java on whatever machine you want. If you don't have some other machine you prefer, you can use attu (javac Test.java to compile the program, java Test to run it).

(2 points) This question is about Java arrays and the covariant typing rule. Look at the skeleton for the "main" method in this class: ArrayExample.java. Add some additional statements to the main method so that the code compiles correctly, and when it is run, it raises a java.lang.ArrayStoreException when adding the cone to geoshapes. (Adding the circle should be OK.) Here is the exception you should get:
```
Exception in thread "main" java.lang.ArrayStoreException: Cone
        at ArrayExample.main(ArrayExample.java:10)
```
Hint: look at the ArrayTest example in the lecture notes.
Next, look at the code in GoodArrayExample.java. (This is exactly the same except for the class name.) Add statements to this code as needed, so that the code compiles correctly, and runs without error.
If you want, you can add some statements to these "main" methods to get them to print something so that you know they are doing something, but you don't need to.

(6 points) This question is about Java generics. Look at the skeleton code in ArrayListExample.java. Add additional methods total_area, total_perimeter, describe_all, and add_empties. Leave the main method untouched. You should get this output when you run the code:

Example with a list of shapes with a circle, a cone, and some empty shapes
Circle[radius=1.0]
Cone[radius=2.0,height=3.0]
Circle[radius=0.0]
Cone[radius=0.0,height=0.0]
Rectangle[width=0.0,height=0.0]
Sphere[radius=0.0]
Total number of shapes: 6

Example with a list of rectangles
Rectangle[width=2.0,height=3.0]
Rectangle[width=5.0,height=5.0]
Total number of shapes: 2
total area of rectangles: 31.0
total perimeter of rectangles: 30.0

Example with a list of 2d shapes with a circle and a rectangle
Rectangle[width=10.0,height=10.0]
Circle[radius=2.0]
Total number of shapes: 2
total area of flat shapes: 112.56637061435917