02115   Java Programming
Autumn 2011

Preparations for the week

Details on handling fixtures - section 6.4.4 (pages 185-186) - should be studied carefully. And as told on the plan for last week in the section After the lectures: Don't forget the remaining parts of the chapter (pages 186-200). Those parts could be useful in relation to doing the coming mandatory assignment.


The situation for the subjects of Chapter 7 is that the practical things have been demonstrated together with some reasons for making the improvements of the design and implementation of the zool game. But I left out the general concepts and much of the important background reasoning:

• Section 7.7 (starting at page 217) on Responsibility-driven design focuses on the idea that each class should be responsible for handling its own data, which leads to a low degree of coupling.
• The importance of following the concept of Localizing change, section 7.8, page 220, is stated. When followed later modifications require changes of only one class.
• Implicit coupling is when one class depends on internal information of another, but this dependence is not obvious, section 7.9 (pages 220-224). Thus it's often a problem to avoid implicit coupling.
• The advices on Thinking ahead and on achieving Cohesion, pages 224-228.
• The very important stated aspects of refactoring and particular the illustrative example of section 7.12.2 (pages 228-232).
• The summary of Design guidelines, section 7.14 (page 237).
• The concept of and implications of using class methods, section 7.15 (pages 238-240), including the main() method, section 7.15.2.

In this week one qustion is: How to avoid duplicate code and fields in a number of related classes ?
    Use inheritance from a common super class.


Inheritance is the subject of Chapters 8 and 9. To be introduced just study Chapter 8 of BK to the following extent:

1. Chapter 8: 8.1 - 8.5; pages 245-264:
   • Read the chapter introduction and section 8.1, pages 245-256
     Work through the exercises 8.1 and 8.2
   • Read section 8.2, pages 256 and 257, to be introduced to inheritance. Figure 8.5 on page 256 shows common fields and methods extracted from classes CD and DVD, Figure 8.2 - page 247, and put into the common super class Item
   • Read section 8.3, pages 257 and 258
   • Read section 8.4, pages 258-262
     Work through the exercises 8.4 and 8.5
   • Read section 8.5, pages 262-264

The lectures

Exercises at the PC's

• Chapter 8:
  Exercises 8.7, 8.8, 8.12 and 8.13, and (for the more experienced student) 8.16
• Chapter 9:
  Exercises 9.3, 9.4 and 9.7, and (for the more experienced student) 9.9 - 9.11

1. Open BlueJ and ask for New Project
2. Give the project a name - as e.g. Example60
3. Then Close the project
4. In the file system the project Example60 is a directory to which you has to copy the file Example60.java from the collection of ready-to-run programs from the Java Precisely textbook
5. Then in BlueJ choose Open Project on project Example60 which now holds the class Example60
6. Compile the Java class
7. Right click on Example60 and select the method void main(String[]) to execute

After the lectures

At the end of this week you are supposed to be familiar with the following parts of the BK textbook:

• Chapter 8: Pages 245-275. Also remember to read page 274-275 with the Summary, including the terms and the Concept summary in order to check that you are familiar with what has been introduced in the chapter. If some terms and/or concepts are not familiar to you, then look up the descriptions in the chapter.
  Do Exercise 8.11 (page 265)

  The implications of inheritance are important as can be read in sections 8.7 and 8.8 (pages 265-271)
  Autoboxing and wrapper classes are introduced in section 8.9 of the BK textbook. Relate to section 5.4 of PS

  Section 8.10 (page 273) relates inheritance to the Java library definitions of the collections classes - relate that desciption to the overview of PS (page 92, lower part)

  Section 8.11 (pages 273-275)
  Do Exercise 8.18

• Chapter 9: Pages 276-299.
  Be aware of the methods declared in the ultimate super class of Java, the Object class:
  • toString in section 9.7, pages 287-290
    Relate to PS, page 10, fifth bullet
  • equals and hashCode in section 9.8, pages 290-292
    Relate to PS, section 22.8 (page 104) and the Examples 133 and 134, page 105
  Don't forget the last sections of the chapter (pages 292-299)
  Work through Exercises 9.12 and 9.13

• Section 5, the first four subsections, pages 4 and 5
• Section 9.5, pages 22 and 23, with exclusion of what is stated about
  • o.super(actual-list); when C's superclass B is an inner class
  • the throws-clause
  Abstract classes are not yet covered by the BK textbook, but besides that Example 27 should not cause any problems.
  Read and run Example 28