CS2 Data Structures Activity

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CS2 Data Structures Activity


Using the HFOSS OpenMRS project to illustrate the use of data structures in a complex system.


CS1 and Java

After successfully completing this activity, the learner should be able to:
  1. Describe the difference between a data structure and the implementation thereof.
  2. Explain the application of a data structure in a specific large complex software system.
  3. Evaluate tradeoffs in selection of data structures.
  4. Analyze the time complexity of an algorithm that uses the data structure.
Process Skills

What process skills will the student practice while completing this activity?


Data structures are widely used in the development of large complex software systems. The decision to use a particular data structure is made by the programmer or in many cases a development team. Several factors must be considered including storage requirements, time requirements of the various operations that will be performed on the data, and usage patterns (i.e. the number and order of deletions, insertions, updates, etc.).

This activity will explore a class within the OpenMRS code base where a number of data structures are utilized. As such, it is expected that the students will have some general knowledge about the OpenMRS project.


  1. Go to the DataExportFunctions class and examine the import statements found at the beginning of the file. Provide the class names of four data structures that are used in DataExportFunctions.java. Note: You may need to refer to the Java APIs and should recall that an interface is not a class.
  2. Go to the following link and then answer the questions below:
    1. What is meant by the term key? The term value?
    2. Given,
      Map<String, int> populations = new HashMap<String, int> ();
      populations.put(“11530”, 27273);
      populations.put(“28601”, 50026);
      populations.put(“38111”, 41742);
      What would the following call to the get method return?
      System.out.println(“The population for Memphis, TN is “ + populations.get(“38111”);
    3. If you wanted to store student information such as a student id, name, major, and gpa, which one of these would you choose as a key? Given that choice of a key, which of the remaining ones could be used as the associated value?
  3. The data structures within the DataExportFunctions class are used in a multitude of ways and it is likely that you are unfamiliar with some of the syntax. Go to the clearMap method. You will find that it uses wildcard characters (‘?’).
    Briefly explain what each of the following means and explain the benefit of using them.
    1. ‘?’ (hint: wildcards)
    2. ‘? Extends Map’
    3. Determine whether each of the following calls to clearMap is valid or invalid. If a call is invalid, explain why.
      1. Map =
      2. Call 2
      3. Call 3
      4. Call 4
    4. Write a Javadoc comment for the clearMap method.
  4. Go to the getLastEncounterAttr method. There are two reference variables declared, types and encounterTypes.
    1. Can you determine what type of object each refers to? If yes, then specify the type of object. If not, then in your opinion what type of object is it most likely to refer to. Explain your answer.
    2. Why do you think these data structures were selected by the developers?
  5. Analysis question…I’m not sure this method is a good choice for analysis. Thoughts? Would some other code segment within this class be better suited for this type of question?


Written artifact to Instructor


How will the activity be graded?

How will learning will be measured?

Include sample assessment questions/rubrics.

Criteria Level 1 (fail) Level 2 (pass) Level 3 (good) Level 4 (exceptional)
The purpose of the project
Why the project is open source


  1. You may choose to leave out analysis.
  2. Depending on how many data structures you have covered, you may choose to reduce the number of data structures you are asking your students to identify.
  3. This activity may be useful even for students who are not learning Java. For example, students who know C++ can, with reasonable effort, can learn enough about Java to complete the activity. The added benefit is that they can learn that concepts transcend the language.

Additional Information

Area & Unit(s)

Programming Languages / Object-Oriented Programming


Using collection classes



Estimated Time
to Complete

Varies, designed as one assignment or laboratory activity

Environment /

Access to OpenMRS codebase


Darci Burdge, Patricia Ordóñez, Jeff Ward, Mezei Razvan, Stewart Weiss, Joanna Klukowska


POSSE 201405 Workshop Activity


This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License

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Suggestions for Open Source Community:

Suggestions for an open source community member who is working in conjunction with the instructor.

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