Exploring accessibility and visibility relationships in java

ABSTRACT

Inheritance and polymorphism are important OOP topics in CS1 and CS2. While these concepts are generally straightforward, there are subtleties that may leave students confused. For example, accessibility of a field in an object is generally determined by the declaring type and access modifiers of the field, and the context in the executing program from which the field is referenced. The dynamic object viewers in jGRASP have been expanded to allow the user to: (1) change the declared type of the object reference to any compatible type and (2) change the accessibility context of the object reference. These options enable the user to explore accessibility and visibility relationships by experimenting with any object on the workbench or in the debugger. Symbols, color, and text are used in the viewer to indicate inheritance relationships, accessibility, and visibility of fields and methods. Initial classroom use has demonstrated the potential for these new viewer features as an aid to students who are learning about inheritance and polymorphism.

REFERENCES

• 1: James H. Cross, II , T. Dean Hendrix , Jhilmil Jain , Larry A. Barowski, Dynamic object viewers for data structures, Proceedings of the 38th SIGCSE technical symposium on Computer science education, March 07-11, 2007, Covington, Kentucky, USA
• 2: Nell Dale. SIGCSE Members Survey. http://www.cs.utexas.edu/users/ndale/ContentResults.html
• 3: John Lewis, Myths about object-orientation and its pedagogy, Proceedings of the thirty-first SIGCSE technical symposium on Computer science education, p.245-249, March 07-12, 2000, Austin, Texas, United States
• 4: Rachel Or-Bach , Ilana Lavy, Cognitive activities of abstraction in object orientation: an empirical study, ACM SIGCSE Bulletin, v.36 n.2, June 2004 [doi>10.1145/1024338.1024378]
• 5: Deborah J. Armstrong, The quarks of object-oriented development, Communications of the ACM, v.49 n.2, p.123-128, February 2006 [doi>10.1145/1113034.1113040]
• 6: Antero Taivalsaari, On the notion of inheritance, ACM Computing Surveys (CSUR), v.28 n.3, p.438-479, Sept. 1996 [doi>10.1145/243439.243441]
• 7: Kate Sanders , Lynda Thomas, Checklists for grading object-oriented CS1 programs: concepts and misconceptions, Proceedings of the 12th annual SIGCSE conference on Innovation and technology in computer science education, June 25-27, 2007, Dundee, Scotland
• 8: Amela Karahasanović , Richard C. Thomas, Difficulties experienced by students in maintaining object-oriented systems: an empirical study, Proceedings of the ninth Australasian conference on Computing education, p.81-87, January 30-February 02, 2007, Ballarat, Victoria, Australia
• 9: Axel Schmolitzky, Teaching inheritance concepts with Java, Proceedings of the 4th international symposium on Principles and practice of programming in Java, August 30-September 01, 2006, Mannheim, Germany [doi>10.1145/1168054.1168084]
• 10: Robert Biddle , Ewan Tempero, Explaining inheritance: a code reusability perspective, Proceedings of the twenty-seventh SIGCSE technical symposium on Computer science education, p.217-221, February 15-17, 1996, Philadelphia, Pennsylvania, United States
• 11: Michael R. Wick , Daniel E. Stevenson , Andrew T. Phillips, Using an environment chain model to teach inheritance in C++, Proceedings of the 33rd SIGCSE technical symposium on Computer science education, February 27-March 03, 2002, Cincinnati, Kentucky
• 12: Anna Eckerdal , Michael Thuné, Novice Java programmers' conceptions of "object" and "class", and variation theory, Proceedings of the 10th annual SIGCSE conference on Innovation and technology in computer science education, June 27-29, 2005, Caparica, Portugal
• 13: Kathryn E. Gray , Matthew Flatt, ProfessorJ: a gradual introduction to Java through language levels, Companion of the 18th annual ACM SIGPLAN conference on Object-oriented programming, systems, languages, and applications, October 26-30, 2003, Anaheim, CA, USA [doi>10.1145/949344.949394]

INDEX TERMS

Primary Classification:
  K. Computing Milieux
  K.3 COMPUTERS AND EDUCATION
      K.3.2 Computer and Information Science Education
          Subjects: Computer science education

General Terms:
Human Factors, Languages

Keywords:
inheritance, jGRASP, object viewers, object-oriented programming, polymorphism, visualization