EECS2030E Test 3

Version D

You have 80 minutes to complete this test. This is a closed book test.

GETTING STARTED

  1. Start eclipse.
  2. Download this project file.
  3. Import the test project by doing the following:
    1. Under the File menu choose Import...
    2. Under General choose Existing Projects into Workspace and press Next
    3. Click the Select archive file radio button, and click the Browse... button.
    4. Navigate to your home directory (the file chooser is probably in the workspace directory).
    5. Select the file test3D.zip and click OK
    6. Click Finish.
  4. All of the files you need for this test should now appear in eclipse.
  5. Open a terminal. You will use this terminal to submit your work.
  6. Copy and paste the command cd workspace/Test3D/src/test3 into the terminal and press enter.

Resources

SOLUTION with list
SOLUTION with map

Question 1 (18 marks total)

IMPORTANT NOTE: You are not given the fields needed to implement the class in this question. You must analyze the API of the class, decide what fields are required, and add the fields to the class.

Implement the class described by this API. You do not have to include javadoc comments.

submit 2030L secEtest3D OwnedPiggyBank.java

Question 2 (12 marks total)

A. (6 marks)

Recall that you used the Owner class in the programming question for this test (see the API here). Consider the following list: 

List<Owner> t = new ArrayList<>();
/* some code not shown that adds many owners to t */

(a): Show how to make a shallow copy of the list t using Java. 

List<Owner> copy = new ArrayList<>(t);

// OR 

List<Owner> copy = new ArrayList<>();
for (Owner w : t) {
  copy.add(w);
}

(b): Is it possible to make a deep copy of t using Java? If so, show how; if not, then explain why the deep copy cannot be made.

No, there is no copy constructor in Owner, and the constructor Owner(String name) makes a new owner that is not equal to any other Owner because its id is guaranteed to be unique.

(c): In your implementation of OwnedPiggyBank, is OwnedPiggyBank an aggregation of an Owner or a composition of an Owner? Explain why you chose to use aggregation or composition for the relationship between the OwnedPiggyBank and its Owner.

It is an aggregation of an Owner because it is impossible to make a copy of an Owner.


B. (3 marks)

Suppose that OwnedPiggyBank had a method named shallowCopy that returned a new list that contained references to the coins that are in the piggy bank. Is there any way for a client to use the list returned by shallowCopy to change the state of the piggy bank (for example, can the client remove coins from the piggy bank by manipulating the returned list, or can the client change the values of the coins in the piggy bank)? If you answer yes, show how the state of the piggy bank can be changed. If you answer no, explain why the state of the piggy bank cannot be changed.

No, the returned list is a new list so modifying the list does not modify the piggy bank's internal collection. Coin is immutable, so it is impossible to change the values of the coins in the returned list or in the piggy bank itself.


C. (3 marks)

OwnedPiggyBank has a serious privacy leak. What is the privacy leak, and what is the implication of this particular privacy leak?

It returns a reference to the owner which allows any client to empty the piggy bank of its coins.


submit 2030L secEtest3D answers.txt