Relational Expression

1
Relational Expression
equal to ! not equal to lt  less than gt 
greater than lt less than or equal to gt
greater than or equal to

• return Boolean results.
• operands must be of numerical types.

2
Logical Expression

• (!a) negation
• (a b) or
• (a b) and

3
Distributive laws

• Original Expression
• (p q) (p r)
• (p q) (p r)

• Equivalent terms
• p (q r)
• p (q r)

4
DeMorgans Laws

• Original Expressions
• !(p q)
• !(p q)

• Equivalent Terms
• (!p) (!q)
• (!p) (!q)

5
Conditional Expression

• condition ? exp1 exp2
• Example
• (x gt 0) ? x -x
• (a gt b) ? a b

6
Postfix/Prefix Operators

•   x (before) expr
  x(after)
• Postfix increment x 1 1
  2
• Postfix decrement x 1 1
  0
• Prefix increment x 1 2
  2
• Prefix decrement --x 1 0
  0

7
Sequence

• Statements are executed top to bottom.
• S1
• S2
• Example
• temp xx yy
• d Math.sqrt(temp)
• x 5
• y 11
• z x y
• System.out.println(z)

8
Block

• a sequence of statements and local variable
  declarations enclosed by braces and
• S1 S2 ... Sn
• Example
•   double temp, d   temp xx yy   d
  Math.sqrt(temp)

9
if Statement

• Execute a block of code (Action) if a condition
  is true. The block of code is executed at most
  once.
• if (condition)
• statements
• Example
• if (x 2 0)
• System.out.println("The number is even.")

10
If-Else Statement.

• if (condition1)
• statement1
• else if (condition2)
• statement2
• else if (condition3)
• statement3
• else
• statement4

• if (condition)
• statement1
• else
• statement2

11
Example if .. else if .. else
String sDay if (day Calendar.SUNDAY)
sDay "Sunday" else if (day
Calendar.MONDAY) sDay "Monday" else if
(day Calendar.TUESDAY) sDay
"Tuesday" else if (day Calendar.WEDNESDAY)
sDay "Wednesday" else if (day
Calendar.THURSDAY) sDay "Thursday"
else if (day Calendar.FRIDAY) sDay
"Friday" else if (day Calendar.SATURDAY)
sDay "Saturday" else sDay
"Unknown"
12
Switch Statement

• switch (expression) case value1  
  statement1   break case value2  
  statement2   break case value3  
  statement3   break default   statement4
  

13
Example Day3.java
case Calendar.THURSDAY sDay
"Thursday" break case Calendar.FRIDAY
sDay "Friday" break case
Calendar.SATURDAY sDay "Saturday"
break default sDay "Unknown"
String sDay switch (day) case
Calendar.SUNDAY sDay "Sunday"
break case Calendar.MONDAY sDay
"Monday" break case Calendar.TUESDAY
sDay "Tuesday" break case
Calendar.WEDNESDAY sDay "Wednesday"
break
14
While Loop

• Repeat a block of code while a condition is true.
  There is no limit to the number of times that the
  block can be executed.
• while (condition)
• statements
• When the body of a while statement, or of a for
  statement consists of a single statement, no
  braces are necessary.

15
Examples While Loop
int i 1 while (i lt 20)  
System.out.println(i)   i
//--------------------- int i 20 while (i gt
0)   System.out.println(i)   i--
16
For Loop

• for (initialization condition incrementation)
•   statement(s)

17
Examples For Loop
for (int i 1 i lt 20 i)  
System.out.println(i) //--------------------
------------------- for (int i 20 i gt 0
i--)   System.out.println(i)
18
Do-While Loop
do   statements while (condition)
19
Examples Do-While Loop
int i 1 do   System.out.println(i)  
i while (i lt 20) //-----------------------
------ int i 20 do   System.out.println(i)
  i-- while (i gt 0)
20
Break and Continue

• A break statement in a loop terminates the loop.
• A continue statement in a loop terminates the
  current iteration of the loop, and continue with
  the next iteration of the loop.

21
Examples Break and Continue
int i 0 while (i lt 20)   i   if (i
5 0) break   System.out.println(i)
//------------------------ int i 0 while (i
lt 20)   i   if (i 5 0) continue  
System.out.println(i)
22
Static Methods

• Some of the methods of a class can be declared
  static.
• These methods can be called directly without
  instances of the class.   
• ClassName.methodName(parameters, ...)

23
Reading Input --the Keyboard Class

• The Keyboard class is NOT part of the Java
  standard class library
• The Keyboard class is in package cs1.
• It provides several static methods for reading
  particular types of data from standard input.
• public static String readString()
• public static String readWord()
• public static boolean readBoolean()
• public static char readChar()
• public static int readInt()
• public static long readLong()
• public static float readFloat()
• public static double readDouble()

24
Example AmountDue1
import cs1.Keyboard public class AmountDue1
public static void main(String args) int
qty double price, amountDue
System.out.print(Enter quantity purchased ")
qty Keyboard.readInt() System.out.print(En
ter the unit price ") price
Keyboard.readDouble() amountDue price
qty System.out.println(Amount due "
amountDue)
25
Install Keyboard

• Copy the cs1.jar file
• Paste it in the C\jdk1.3\jre\lib\ext directory
• If the above doesnt work by itself, then also
  paste it in C\Program Files\JavaSoft\JRE\1.3\lib\
  ext

26
Install Keyboard Method 2

• Create a cs1 subdirectory to the directory
  containing your java programs
• Copy Keyboard.java into the cs1 directory
• Homework directory           -Java source
  files           - cs1 subdirectory
                    - Keyboard.java

27
Install Keyboard Method 3

• Copy Keyboard.java into the same directory as
  your programs.

28
Reading Input JOptionPane

• import javax.swing.JOptionPane
• public class AmountDue2
• public static void main(String args)
• int qty
• double price, amountDue
• String temp
• temp JOptionPane.showInputDialog
• ("Please enter the quantity purchased
  ")
• qty Integer.parseInt(temp)
• temp JOptionPane.showInputDialog
• ("Please enter the unit price ")
• price Double.parseDouble(temp)
• amountDue price qty
• JOptionPane.showMessageDialog
• (null,"Amount due " amountDue)

29
Reading Input java.io

• import java.io.
• public class AmountDue3
• public static void main(String args)
• throws IOException
• int qty
• double price, amountDue
• BufferedReader br new BufferedReader
• (new InputStreamReader (System.in))
• System.out.print("Please enter the quantity
  purchased ")
• qty Integer.parseInt(br.readLine())
• System.out.print("Please enter the unit price
  ")
• price Double.parseDouble(br.readLine())
• amountDue price qty
• System.out.println(Amount due "
  amountDue)

30
NumberFormat Class

• x 10000.0/3.0
• System.out.println(x)
• // 3333.3333333333335
• Printing a number with System.out.print(x) will
  normally print the maximum number of non-zero
  digits.
• The NumberFormat class in the java.text package
  can format
• Numbers
• Currency values
• Percentage values

31
Number Format

• import java.text.
• public class FormattedOutput
• public static void main(String args)
• int qty
• double price, amountDue
• double x 10000.0/3.0
• System.out.println("Default output is \t"
  x) // 3333.3333333333335
• NumberFormat num_format
  NumberFormat.getNumberInstance()
• String s num_format.format(x)
• System.out.println("Number format is \t"
  s)// 3,333.333
• NumberFormat cur_format
  NumberFormat.getCurrencyInstance()
• s cur_format.format(x)
• System.out.println("Currency format is
  \t" s)//3,333.33
• NumberFormat per_format
  NumberFormat.getPercentInstance()
• s per_format.format(x)
• System.out.println("Percent format is \t"
  s) // 333,333

32
Other NumberFormat methods

• setMaximumIntegerDigits(int digits)
• setMaximumFractionDigits(int digits)
• setMinimumIntegerDigits(int digits)
• setMinimumFractionDigits(int digits)