Switch Statement and Operator ?

1. CSE110
Principles of Programming
with Java
Lecture 10:
switch Statement and Operator ?
Javier Gonzalez-Sanchez
javiergs@asu.edu
javiergs.engineering.asu.edu
Office Hours: By appointment

2. switch Statement

3. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 3
The switch Statement
• The switch statement provides another means to
decide which statement to execute next
• The switch statement evaluates an expression, then
attempts to match the result to one of several
possible cases
• Each case contains a value and a list of statements
• The flow of control transfers to statement associated
with the first value that matches

4. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 4
The switch Statement
• The general syntax of a switch statement is

5. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 5
The switch Statement
• Often a break statement is used as the last
statement in each case's statement list
• A break statement causes control to transfer to the
end of the switch statement
• If a break statement is not used, the flow of control
will continue into the next case

6. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 6
The switch Statement
• A switch statement can have an optional default case
• The default case has no associated value and simply
uses the reserved word default
• If the default case is present, control will transfer to it if no
other case value matches
• Though the default case can be positioned anywhere in
the switch, usually it is placed at the end
• If there is no default case, and no other value matches,
control falls through to the statement after the switch

7. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 7
The switch Statement
• The expression of a switch statement must result in
an integral type, meaning an int or a char
• It cannot be a boolean value, a floating point value
(float or double)
• A switch statement tries to match the expression
with a value
• You cannot perform relational checks with a switch
statement

8. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 8
Example 1
String s = JOptionPane.showInputDialog(“Write a number”):
int option = Integer.parseInt(s);
switch (option) {
case 1: System.out.println(“Phoenix”); break;
case 2: System.out.println(“NY”); break;
case 3: System.out.println(“Seattle”); break;
default: System.out.println(“Not available”);
}
System.out.println(“Bye.”);

9. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 9
Example 2
String s = JOptionPane.showInputDialog(“Write a letter”):
int letter = s.charAt(0);
switch (letter) {
case 'A':
System.out.println("It is an A");
break;
case 'B':
System.out.println("It is a B");
break;
case 'C':
System.out.println("It is a C");
break;
default:
System.out.println("Invalid option");
}

10. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 10
Example 1
String s = JOptionPane.showInputDialog(“Write your grade”);
int grade = Integer.parseInt(s);
switch (grade) {
case 100: System.out.println(“A+”); break;
case 95:
case 90: System.out.println(“A”); break;
case 85:
case 80: System.out.println(“B”); break;
default: System.out.println(“C”);
}
System.out.println(“Bye.”);
// What is the result for grade = 97 ?

11. The operator ?

12. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 12
The Conditional Operator
• Java has a conditional operator that evaluates a
boolean condition that determines which of two
other expressions is evaluated
• The result of the chosen expression is the result of
the entire conditional operator
• Its syntax is:
condition ? expression1 : expression2
• If the condition is true, expression1 is evaluated; if it
is false, expression2 is evaluated

13. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 13
The Conditional Operator
• The conditional operator is similar to an if-else
statement, except that it forms an expression that
returns a value
• For example:
larger = ((num1 > num2) ? num1 : num2);
• If num1 is greater that num2, then num1 is assigned
to larger; otherwise,num2 is assigned to larger
• The conditional operator is ternary because it
requires three operands

14. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 14
Example
System.out.println ("Your change is "
+ count
+ ((count == 1) ? "Dime" : "Dimes"));
• If count equals 1, then "Dime" is printed
• If count is anything other than 1, then "Dimes" is
printed

15. CSE110 - Principles of Programming
Javier Gonzalez-Sanchez
javiergs@asu.edu
Summer 2017
Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.