02115   Java Programming
Autumn 2011

The Java knowledge of the audience

I much appreciate to have received exercise suggestions by e-mail, but those exercises were unfortunately better suited for a course on Algorithms and data structures. This week the exercises are grouped on different levels by an or

Preparations for the week

• Fields hours, minutes and diplayString are declared (page 68 of BK).
• The two ClockDisplay-constructors both create two NumberDisplay-objects and assign their references to the appropriate fields hours and minutes. At last the diplayString is assigned it's value by use of methods of the class.

Actually, when experimenting with the lab-classes and the mail-system projects, we can figure out that behind the scene a LabClass-object and a MailServer-object must hold fields which refer to flexible object structures capable of holding arbitrary numbers of Student-objects and MailItem-objects, respectively.

This week projects using flexible object structures like lists, sets and maps are introduced. The PS textbook gives an overview of the available structures on page 92. Take a look, but skip syntactic details like List<T>, Set<T> and Map<K,V> and on the figure don't worry about interfaces and abstract classes. Focus on the structure and on the Concrete classes of which BK in the Chapters 4 and 5 introduces the ArrayList<T>, the HashMap<K,V> and the HashSet<T>. The general applicable class types T, K and V are all substituted with class String in the Chapter 4 and 5 BlueJ projects of BK.


Before going on with the BK textbook I presume that you have done what has been stated in Week plan #1.

As a minimal preparation to this week study the Chapters 4 and 5 of BK to the following extent:

1. Chapter 4: 4.1 - 4.6 and 4.12.2 - 4.12.4; pages 87-94 and 117-119:
   • Read the chapter introduction and sections 4.1 - 4.6, pages 87-94
     Work through the exercises 4.1 - 4.6
     Section 4.5 gives you an introduction to the generic class ArrayList<T> showing examples on three specific choices of T, those are String, Person and TicketMachine
   • Read sections 4.12.2 - 4.12.4, pages 117-119, including only the exercises 4.46 - 4.48, in order to be introduced to arrays
2. Chapter 5: 5.1 - 5.3.1, 5.5 - 5.6.2 and 5.7; pages 128-138, 146-149 and 152-153:
   • Read the chapter introduction and sections 5.1 - 5.3.1, pages 128-138
     Don't forget to work through the exercises 5.1 - 5.6 in order to be familiar with the idea of the TechSupport system example and with the use of library classes, here the String class
   • Read sections 5.5 - 5.6.2 (pages 146-149) and only work through the exercises 5.23 and 5.24 in order to be introduced to the important map concept and its particular HashMap implementation
   • Read section 5.7 and do the Exercise 5.32 (pages 152-153) to be introduced to sets and to be aware of the differences between lists, maps and sets

The lectures

Exercises at the PC's

• Chapter 4:
  Either do Exercises 4.12-4.16, 4.28, 4.29 or
  Exercises 4.25-4.27, 4.34-4.35 or
  Exercises 4.36-4.40
• Chapter 5:
  Either do Exercises 5.7-5.9, 5.25-5.30, 5.47-5.50 or Exercises 5.32, 5.37, 4.41 and 5.59-5.60
  For solving 5.37 you may refer to PS section 8.4

After the lectures

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

• Chapter 4: Pages 87-126. Also remember to read 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. supplied with doing the
  Exercises 4.51, 4.52, 4.62
  Example 22 of PS (page 19): The example uses the default initialization value 0.0. Experiment with other values, add loops to print out the contents of the arrays, compile and run.
• Chapter 5: Pages 128-167, with special focus on the sections 5.4, 5.7 and 5.10-5.14
  Exercises 5.12-5.14, 5.31, 5.32, 5.43, 5.59

  Take the tips on how to write documentation - section 5.10. It looks naturally to require that kind of documentation to be carried out in the Mandatory Assignment.

• Section 12.5 on pages 50 and 52
  This section gives an overview of the Java loop statements. By now some of the examples hold details which are not easily understandable.
  Section 12.5.2 (page 50) states the generality of the for-loop introduced in section 4.8.1 of BK (pages 97-99).
  In Code 4.3 of BK (page 97) the field notes is an expression which comply to have type Iterable<t> because an ArrayList is iterable.
• In chapter 22 (page 92) some of the syntactic details should be understandable after having read section 5.4.4 of BK (page 146).
• On an ArrayList-object all methods mentioned on pages 94 and 95 can be applied.
• Section 22.7 on page 102 gives an overview of the proces of iterating over a collection. The main parts of the section can be understood after having read sections 4.8.3 - 4.8.5 on pages 102-105 of BK.
  Have in mind Example 131 (page 103) which is used in Example 70 and Example 71 - to be studied at special occasions.
• Section 8 on pages 16 and 18 is on arrays
  Section 8.1 states the general characteristics on declaring arrays and accessing array. Ought to be fully understandable when sections 4.12.2 - 4.12.4 of BK (pages 117-119) has been read.
  Section 8.3 covers multidimensional arrays (not a subject of the BK textbook) - supply with Example 22 on page 19.
  
• On a HashSet-object all methods mentioned on pages 94 and 96 can be applied.
• On a HashMap-object all methods mentioned on page 98 can be applied.
  The syntactic notions ? extends K and ? extends V are unknown so far.
• Section 22.10 on page 108
  This section gives useful advises on choosing the right kind of collection class or map class depending on the problem to be solved.