TCU CoSc 10403 Programming with Java

1
TCU CoSc 10403 Programming with Java

• Lecture 5
• Program Design Widgets II

2
Agenda

• Last time
• Chapter 3 widgets
• Today
• Program design
• Wormhole design (lablet 2)
• More on color
• Writing your own methods
• More widgets
• Read chapter 3

3
A color review (optional)

• Reference pages 46 53 (wormhole)
• Color myColor new Color(255, 0, 128)
• g.setColor(myColor)
• g.fillRect(10,20,100,200)
• // If dont need to change this color
• g.setColor(new Color(255, 0, 128)
• g.fillRect(10,20,100,200)

4
Scope of variables

• Wormhole, design pass 2 (page 54)
• Instance variables
• Scope is global to the class
• Defined outside any method (at top)
• Local variables
• Scope is local to the method
• Defined inside a method
• Guideline use smallest scope needed to ease
  debugging, understanding

5
Program Design

• Refer to Wormhole, design pass 3 (lablet 2)
• Writing your own methods (drawHole)
• Why?
• Less code (repeated code) see page 58
• Easier to
• Read
• understand
• modify
• reuse

6
Program Design

• Decide
• What the method needs to do and how to do it
  (algorithm)
• Local variables and arguments
• Return type
• Descriptive method name
• Use a VERB PHRASE denotes action
• drawHole, calcGPA, confirmPurchase

7
Widgets

• Lablet 3 Gigobite
• Code review
• View difference when run in appletviewer and Web
  browser
• More examples
• Exercise 8 in chapter 3
• Others