SCANNER CLASS(Methods) DIALOG BOXES Message Dialogs INPUT DIALOGS Disadvantage of JOptionPane Methods for converting strings to numbers DECISION / CONTROL FLOW STRUCTURES IF STATEMENT IF STATEMENT SYNTAX Flow of If statements If-else Statement If –else statement SYNTAX Logic of if-else Statement NESTED IF STATEMENT Nested if statement SYNTAX

1. MMIIDDTTEERRMM CCOOVVEERRAAGGEE
READING KEYBOARD
OUTPUT

2. SSCCAANNNNEERR CCLLAASSSS((RREEFFRREESSHH))
Ex.
Scanner keyboard = new Scanner(System.in)
Declares a
variable
named
keyboard
Creates a Scanner
object in
memory. Read
input from
System.in

3. SSCCAANNNNEERR CCLLAASSSS((MMeetthhooddss))
STRING
Bytes
Integers
Long integers
Short integers
Float
Doubles

4. SSCCAANNNNEERR CCLLAASSSS((MMeetthhooddss))
For example:
int number;
Scanner keyboard= new Scanner(System.in);
System.out.print(“Enter an integer value”);
number= keyboard.nextInt();
Therefore, this statement formats the input
that was entered @ the keyboard as an
int.

5. SSCCAANNNNEERR CCLLAASSSS((MMeetthhooddss))
 nextByte – returns input as Byte
 nextDouble – returns input as Double.
 nextFloat – returns input as Float
 nextInt – returns input as an Int
 nextLine – return input as String.
 nextLong – return input as a long
 next Short – return input as a short.

6. SSCCAANNNNEERR CCLLAASSSS((MMeetthhooddss))
EXAMPLE IMPLEMENTATION
Payroll.java

7. DDIIAALLOOGG BBOOXXEESS
CONCEPT:
JOptionPane class allows a user to display
a Dialog Box.
Dialog Box – is a small graphical window
that displays a message to the user or
request input. We can quickly display
dialog boxes w/ JOptionPane class.

8. DDIIAALLOOGG BBOOXXEESS
Types of DIALOG BOXES
Message Dialog – a dialog box that
displays a message; an OK button is also
displayed.
Input Dialog – dialog box tat prompts the
user for input & provides text field where
input is typed; an OK button and a
CANCEL button are also displayed.

9. DDIIAALLOOGG BBOOXXEESS
Beginning Statement in your code when
using JoptionPane:
import javax. swing.JOptionPane;
Purpose: this statement tells the compiler
where to find the JOptionPane class, and
make it available to your program.

10. MMeessssaaggee DDiiaallooggss
 showMessageDialog method- is used to display a
message dialog box.
Statement to call the method:
JOptionPane.showMessageDialog (null, “HELLO WORLD”);
ARGUMENT PURPOSE:
null – causes the dialog box to be displayed in the center of the
screen.
HELLO WORLD – the message we want to display in the dialog
box.

11. IINNPPUUTT DDIIAALLOOGGSS
 showInputDialog method – to display an input
dialog in JOptionPane class.
Statement to call the method:
String name;
name = JOptionPane.showInputDialog(“Enter your name.”);

12. SSaammppllee CCooddee
import javax.swing.JOptionPane;
public class Names {
public static void main (String [ ] args)
{
firstName= JOptionPane.showInputDialog(“What’s your firstname”);
middleName=JOptionPane.showInputDialog(“What’s your middle name”);
lastName=JOptionPane.showInputDialog(“What’s your Last Name”);
JOptionPane.showMessageDialog(null, “HELLO” +firstName + “ “ +
middleName + “ “ + lastName);
System.exit (0); This statement causes the program to end, & is
required if we use the JOptionPane class to display dialog
box.
} }

13. DDiissaaddvvaannttaaggee ooff JJOOppttiioonnPPaannee
JOptionPane class does not have different
methods for reading values of different data
types as input.
 showInputDialog method always returns the
user’s input as a String.
Problem when use in Math operation.
Because we cannot perform math on strings.
In such case, you must convert the input to a numeric
value.

14. Methods ffoorr ccoonnvveerrttiinngg ssttrriinnggss ttoo nnuummbbeerrss
Byte.parseByte – method to convert string to a
byte.
Double.parseDouble – method to convert string
to a double.
Float.parseFloat – method to convert string to a
float.
Integer.parseInt – method to convert string to
an int.
Long.parseLong – method to convert string to a long.
Short.parseShort – method to convert string to a
short.

15. SSaammppllee UUssaaggee
 int num;
String str;
str=JOptionPane.showInputDialog(“Enter a number”);
num= Integer.parseInt(str);
num variable will hold the value entered by
the user, converted to an int.

16. DDEECCIISSIIOONN // CCOONNTTRROOLL
FFLLOOWW SSTTRRUUCCTTUURREESS

17. IIFF SSTTAATTEEMMEENNTT
CONCEPT:
> is used to create decision structures,
which allow the program to have more
than one path of execution
> causes one or more statements to
execute only when boolean expression
is true.
NOTE: RELATIONAL OPERATIONS ARE USED

18. IIFF SSTTAATTEEMMEENNTT SSYYNNTTAAXX
If (BooleanExpression)
statement;
BooleanExpression- appears inside the
parentheses must be a boolean
expression.
If the boolean expression is true, the next
statement is executed.

19. FFllooww ooff IIff ssttaatteemmeennttss

20. SSAAMMPPLLEE UUSSAAGGEE
PROBLEM:
If the value is less than 32, displays the
message “Invalid Number”
CODE:
if ( value < 32)
System.out.println(“Invalid Number”);

21. IIff--eellssee SSttaatteemmeenntt
Concept:
> will execute one group of statements if
its BOOLEAN EXPRESSION is True, or
another group if its BOOLEAN
EXPRESSION is False.
> expansion of the if statement.

22. IIff ––eellssee ssttaatteemmeenntt SSYYNNTTAAXX
if(BooleanExpression){
statement;
} else {
statement;
}

23. LLooggiicc ooff iiff--eellssee SSttaatteemmeenntt

24. NNEESSTTEEDD IIFF SSTTAATTEEMMEENNTT
CONCEPT:
> To test more than one
condition, an if statement can
be nested inside another if
statement.

25. NNeesstteedd iiff ssttaatteemmeenntt SSYYNNTTAAXX
if (BooleanExpression)
{
if(BooleanExpression)
{
statement;
}
else
{
statement;
}
else
{
statement;
}

26. TTHHEE iiff--eellssee--iiff SSttaatteemmeenntt
CONCEPT:
 if-else-if statement test a
series of conditions than with
a set of nested if-else
statement.
 else-if statement is in between
the if & else statement.

27. SSyynnttaaxx ooff iiff--eellssee--iiff SSttaatteemmeenntt
if(BooleanExpression){
statement;
}
else if(BooleanExpression){
statement;
}
else{
statement;
}
main test
Alternative
test if the if
statement is
false

28. LLOOGGIICCAALL OOPPEERRAATTOORRSS
Java provides two binary operators,
&& and ||, which are used to
combine two boolean expressions
into a single expression.
Java also provides the unary !
operator, which reverses the truth
of a boolean expression.

29. TTrruutthh ttaabbllee ooff tthhee &&&& ooppeerraattoorr
EXPRESSION VALUE
true&&false false
false&&true false
false&&false false
true&&true true

30. TTrruutthh ttaabbllee ooff tthhee |||| ooppeerraattoorr
EXPRESSION VALUE
true|| false true
false|| true true
false|| false false
true|| true true

31. LLOOGGIICCAALL OOPPEERRAATTOORRSS IINN OORRDDEERR OOFF
PPRREECCEEDDEENNCCEE
1st = !
2nd=&&
3rd= ||
Note: ! Operator has higher precedence than
many of Java’s other operators.
You should enclose its operand in () unless
you intend to apply it to a variable or simple
expression w/ no other operators.

32. EExxaammppllee UUssaaggee
Assume x is an int w/ a value stored in it:
! (x >2)
read as “ is x not greater than 2?”
!x>2
read as “ is logical complement of x is
greater than 2? ”
Note: ! operator can be applied only to boolean
expressions.

33. SSwwiittcchh SSttaatteemmeenntt
CONCEPT:
switch statement lets the value of a
variable or expression determine where
the program will branch to.
 is a multiple alternative decision
structure.
can be used as an alternative of if-else-if
statement that test the same variable w/
several different values.

34. SSttrruuccttuurree

35. SSwwiittcchh ssttaatteemmeenntt ssyynnttaaxx
switch(variable)
{
case value_1:
statement;
break;
case value_N : statement;
break;
default :
statement;
break;
}
These statement is executed if
the variable is equal to value_1
These statement is executed if the
variable is equal to value_N.
These statement is executed if
the variable is not equal to
any of the case values.

36. SSaammppllee UUssaaggee((fflloowwcchhaarrtt eexxaammppllee))
switch(month)
{
case 1:
System.out.print(“January”);
break;
case 2:
System.out.print(“February”);
break;
case 3:
System.out.print(“March”);
break;
default:
System.out.print(“Error:”);
break;
}