College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
Module 9
CONTROL STRUCTURES
Learning Objectives:
At the end of this lesson, the students shall be able to:
1. Learn how to use switch structure which allows a variable to be tested
for equality against a list of values.
2. Create a Java program using switch structure.
 A switch statement allows a variable to be tested for equality against a list
of values. Each value is called a case, and the variable being switched on
is checked for each case.
Syntax:
switch(expression) {
case value 1 :
// Statements 1
break;
// optional
case value 2 :
// Statements 2
break;
// optional
// You can have any number of case statements.
}
default :
// Statements
// Optional
The following rules apply to a switch statement −
 The variable used in a switch statement can only be integers,
convertible integers (byte, short, char), strings and numbers.
1|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java






You can have any number of case statements within a switch.
Each case is followed by the value to be compared to and a colon.
The value for a case must be the same data type as the variable
in the switch and it must be a constant or a literal.
When the variable being switched on is equal to a case, the
statements following that case will execute until a break
statement is reached.
When a break statement is reached, the switch terminates, and
the flow of control jumps to the next line following the switch
statement.
Not every case needs to contain a break. If no break appears,
the flow of control will fall through to subsequent cases until a
break is reached.
A switch statement can have an optional default case, which
must appear at the end of the switch. The default case can be
used for performing a task when none of the cases is true. No
break is needed in the default case.
Flow Diagram
Expression
True
Case 1
Statement
break
Statement
break
Statement
break
Statement
break
False
True
Case 2
False
True
Case 3
False
True
Case 4
Statement after switch
2|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
Example 1:
public class Test {
public static void main(String args[])
{
char grade = 'C';
switch(grade) {
case 'A' :
System.out.println("Excellent!");
break;
case 'B' :
case 'C' :
System.out.println("Well done");
break;
case 'D' :
System.out.println("You passed");
case 'F' :
System.out.println("Better try again");
break;
default : System.out.println("Invalid grade");
}
System.out.println("Your grade is " + grade);
}}
Output:
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College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
Example 2:
import javax.swing.JOptionPane;
public class SwitchSample1 {
public static void main(String args[]) {
int day=Integer.parseInt(JOptionPane.showInputDialog("Enter day: "));
String dey;
switch(day) {
case 1: dey = "Sunday";
break;
case 2: dey = "Monday";
break;
case 7: dey = "Saturday";
break;
default:
dey = "Invalid";
}
JOptionPane.showMessageDialog(null,"Today is: " + dey);
}}
4|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
Example 2:
import javax.swing.JOptionPane;
public class SwitchSample2 {
public static void main(String args[]) {
char month = JOptionPane.showInputDialog("Enter month: ").charAt(0);
String dey;
switch(month) {
case '1': dey = "January"; break;
case '2': dey = "February"; break;
case '7': dey = "July"; break; default: dey =
"Invalid";
}
JOptionPane.showMessageDialog(null,"The month is: " + dey);
}}
5|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
Example 3:
import javax.swing.JOptionPane;
public class SwitchSample3 {
public static void main(String args[]) {
char sex = JOptionPane.showInputDialog("Enter sex: ").charAt(0);
String gender;
switch(sex) {
case 'M':
case 'm': gender = "Male"; break;
case 'f':
case 'F': gender = "Female"; break;
default: gender = "Invalid";
}
JOptionPane.showMessageDialog(null,"You are: " +
gender);
}}
6|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
charAt( ) method is used in Example #’s 2 & 3
The method charAt(int index) returns the character at the specified index. The index value should
lie between 0 and length()-1.
Example:
char month = JOptionPane.showInputDialog("Enter month: ").charAt(0);
char month = JOptionPane.showInputDialog("Enter month: ").charAt(0);
would return the first character of the input value.
charAt() Method

Description
This method returns the character located at the String's
specified index. The string indexes start from zero.

Syntax
Here is the syntax of this method − public char charAt(int
index)

Parameters
Here is the detail of parameters −
• index − Index of the character to be returned.
• Return Value − This method returns a char at the
specified index.

Example
public class Test {
public static void main(String args[]) {
String s = "Strings are immutable";
char result = s.charAt(8);
System.out.println(result);
}}

This will produce the following result −
Output
a
7|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
Example 4
public class CharAtExample {
public static void main(String args[]) {
String str = "Welcome to string handling tutorial";
char ch1 = str.charAt(0);
char ch2 = str.charAt(5);
char ch3 = str.charAt(11);
char ch4 = str.charAt(20);
System.out.println("Character
System.out.println("Character
System.out.println("Character
System.out.println("Character
at 0 index is: "+ch1);
at 5th index is: "+ch2);
at 11th index is: "+ch3);
at 20th index is: "+ch4);
}}
Character at 0 index is: W
Character at 5th index is: m
Character at 11th index is: s
Character at 20th index is: n
The method charAt(int index) returns the character at the specified index. The
index value should lie between 0 and length()-1.
Reference/s:

JEDI Course Notes

https://www.tutorialspoint.com/java/number_equals.htm

https://beginnersbook.com/2013/12/java-string-charat-method-example/
8|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
Name:
Course/Year:
Score:
Date:
SEATWORK EXERCISE MPT3
(switch)
Week 10:
Screen shot the output of the following snippet:
1.
9|Page
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
2.
10 | P a g e
College of Computer Studies and Engineering
INFORMATION TECHNOLOGY DEPARTMENT
ITC c105 – Computer Programming using Java
3
11 | P a g e