Programming Exercise 5

In this exercise, you will get some practice with interfaces:

• Start by examining the StrangeDataStructure.java interface. You can also look at the Javadoc version.
  • Notice that the interface has a number of methods.
  • You are to write an object called StrangeDataStructureImpl.java that will implement the methods. Start by using this template.
  • The code for testing is in TestStrangeDataStructure.java.
• The test code shows that:
  • Some integers will be fed into the data structure, using the addElement() method.
  • The sum of these integers is requested from the the data structure, using the getSumOfElements() method.
  • There are two enumerations, that are invoked using the methods oddElements() and evenElements().
• Your code in StrangeDataStructureImpl.java will implement the interface:
  • This means you will have to implement every method in the interface.
  • You will need to store the integers fed to you. You can use whatever internal data structure you like, including library data structures, but should be prepared for a large (and unknown) size, even if the test in TestStrangeDataStructure is small.
• The addElement() and getSumOfElement() methods seem straightforward, so let's consider oddElements:
  • Notice that the return type is an Enumeration, which is itself an interface.
  • Thus, you will need to return an object that implements the Enumeration interface.
  • Recall that the Enumeration interface has two methods:

           public interface Enumeration {
              public boolean hasMoreElements ();
              public Object nextElement ();
           }
         

    Your enumeration object will walk through the data structure in such a way that every call to nextElement() will return one of the odd integers stored.
  • By successively calling nextElement() it should be possible to "enumerate" all the odd integers stored.
• The evenElements() method is analogous.
• Suggestion: start by getting the first two methods working, then do the odd-elements enumeration, and then the even one. You can comment out appropriate portions of the test code for this purpose.

Deliverables and submission:

• The source code for your program. Please write all your code in the same file, StrangeDataStructureImpl.java
• NOTE: Your code will be graded on both correctness and documentation (comments).
• Follow the submission instructions carefully.
• Draw a complete memory picture (in PDF) just before the start of the first while-loop. You do not need to show all the elements in the data structure, just the first few. But you do need to show the different kinds of objects.