1. Part II The Switch Statement

2. The switch Statement Provides alternative to if-else chain
For cases that compare value of integer expression to specific value
Reserved words:
switch
case
default
break

3. The switch Statement (continued)
Syntax:
switch (expression)
{ // start of compound statement
case value-1: < terminated with a colon
statement1;
statement2;
break;
case value-2: < terminated with a colon
statementm;
statementn;
default: < terminated with a colon
statementaa;
statementbb;
} // end of switch and compound statement

4. The switch Statement (continued)
Once entry point has been located :
All further case evaluations are ignored
Execution continues through end of compound statement
Unless break statement is encountered
break statement
Causes immediate exit from switch statement

5. import javax.swing.*;
public class SelectDiskMaker {
public static void main(String[] args)
String s1, outMessage;
int code;
s1 =JOptionPane.showInputDialog("Enter a number:");
code = Integer.parseInt(s1);
switch (code)

6. import javax.swing.*;
public class SelectDiskMaker {
public static void main(String[] args)
String s1, outMessage;
int code;
s1 =JOptionPane.showInputDialog("Enter a number:");
code = Integer.parseInt(s1);
switch (code) {
case 1:
outMessage = "3M Corporation";
break;
case 2:
outMessage = "Maxell Corporation";
case 3:
outMessage = "Sony Corporation";
case 4:
outMessage = "Verbatim Corporation";
default:
outMessage = "An invalid code was entered";
} // end of switch

7. JOptionPane.showMessageDialog(null, outMessage,
"Program 4.6",
JOptionPane.INFORMATION_MESSAGE);
System.exit(0);
} // end of main()
} // end of class

8. Program Design and Development: Introduction to UML
Explicit design
Should always be undertaken before coding begins
Referred to as program modeling
Unified Modeling Language (UML)
Program modeling language with its own set of rules and notations
Not part of Java language

9. Program Design and Development: Introduction to UML (continued)
Must understand and specify:
What objects in system are
What can happen to objects
When it can happen
Each item addressed by number of individual and separate views and diagrams

10. Class and Object Diagrams
Class diagrams
Used to describe classes and their relationships
Object diagrams
Describe specific objects and relationships
Attribute
Characteristic that each object in class must have
Attribute type
Primitive
Or class type

11. Class and Object Diagrams (continued)
Visibility
Defines where attribute can be seen
Whether attribute can be used in other classes or is restricted to class defining it
Operations
Transformations that can be applied to attributes
Ultimately coded as Java methods

12. Class and Object Diagrams (continued)
Figure 5.9: A class and object representation

13. Relationships (continued)
Figure 5.17: A multilevel aggregation

14. Relationships (continued)
Figure 5.18: A generalization relationship

15. Common Programming Errors
Assuming if-else statement selecting incorrect choice when problem is values being tested
Using nested if statements without including braces to clearly indicate desired structure
Inadvertently using assignment operator = in place of relational operator == when comparing Boolean data
Forgetting to use break statement to close off case within switch statement

16. Summary Relational expressions if-else statements
Referred to as conditions
Used to compare operands
if-else statements
Used to select between two alternative statements
Based on value of relational or logical expression
Can contain other if-else statements

17. Summary (continued) Compound statement switch statement
Number of individual statements enclosed within brace pair { and }
switch statement
Multiway selection statement

18. End of Chapter 5 Be ready to review chapter questions for Thursday
Submit topic for presentation
work on today’s lab