1. Introduction to Java
IST 311 / MIS 307

2. Java
Three flavors:
Java Standard Edition (Java SE) – client-side standalone application or applets
Java Enterprise Edition (Java EE) – server-side applications like servlets & JavaServer Pages (JSP)
Java Micro Edition (Java ME) – mobile devices like cell phones

3. Java Java SE 6 – latest version
Java Development Toolkit (JDK)
JDK 1.6 (Java 6 or JDK 6)
Set of programs for developing & testing Java programs from command line
Integrated Development Environment (IDE)
Eclipse for editing, compiling, building, & debugging programs

4. Java
Examples in textbook include line numbers. Feature which may be turned on or off in Eclipse.
Source code
Right click to bring up list
Select Preferences
Click on link to Text Editors
Check mark on Line Numbers
Click OK

5. Objects An object has structure Attributes (characteristics)
Behaviors or operations it can carry out (actions)

6. Class Definition A Java program is written as a class definition
A Java application is a class that contains a main( ) method

7. Class Definition Import Declaration
Statements to identify the predefined classes used in a Java program
Import declarations must appear before the class declaration
Most Java API’s begin with either “java” (core classes) or “javax” (optional classes)
import javax.swing.JOptionPane;
import java.io.*;

8. Class Definition Class Definition has two parts: Class Header
Class’s name; must be the same name as the .java file
Accessibility as public or private
Pedigree which specifies where it fits in the Java class hierarchy; default is Object class
Class Body
Enclosed within curly brackets { }
Contains instance variables to store data
Contains methods for the actions or behaviors

9. Class Definition Identifier – name for a class, method, or variable
Must begin with a letter, A to Z, or a to z, an underscore (_), or a dollar sign ($); don’t use $ for your identifiers
May be followed by any number of letters, digits, 0 to 9, an underscore, or dollar sign
May not use a Java keyword (see Appendix A, pg. 709)
Java is case sensitive
taxrate vs. TaxRate

10. Class Definition Data Types – two types in Java
Primitive Data Types (pg.32, Table 2.2)
boolean char
byte short
int long
float double
Objects or Reference Variables– programmer created through a class definition
String is an object and therefore a data type

11. Class Definition
Variables – named storage location in memory where a value of a given data type may be stored

12. Start Lab 2

13. Class Definition Method Definition
Code that carries out a specific task or behavior of the class
Method heading and body
Heading contains
the name
accessibility as public, private, or protected
type of data returned by the method
list of parameters

14. Class Definition Method Definition Body contains Executable statements
System.out.print(“Hello.”):
Local variable declarations
Computations or assignment statements
sum = num1 + 5;
Calls to other methods
Return statements
return sum;

15. Flow of Control: Methods

16. Input from Keyboard Input is complicated task
Things can go wrong
User types a letter instead of a number
File could be missing
Java has three I/O streams at startup
System.in : refer to standard input device (keyboard)
System.out : refer to standard output device (display)
System.err

17. Input from Keyboard
java.util.Scanner class has a list of methods for data types(pg. 27)
nextByte( )
nextInt( )
nextDouble( )
next( )
nextLine( )
Scanner input = new Scanner(System.in);
double radius = input.nextDouble();

18. Scanner Class Selects chunks of data from input stream
Stops at the delimiter
Default delimiter = white space
Space, tab, return, newline characters
What happens when type full name in program?

19. Output
In Java, any source or destination for I/O is considered a stream of bytes or characters
To perform output, we insert bytes into the stream
I/O is handled through methods that belong to classes contained in:
java.io package

20. Output java.io.PrintStream class contains methods
println( ) //prints a line feed after data
System.out and System.err can be used to write things to the console
System.out.print(“Hello”);

21. Math Operation Operator Java Addition + x + 2 Subtraction - m – 2
Multiplication *
a * 3
Division /
x / 2
Modulus %
x % y

22. Assignment Statements
Value are placed into variables using assignment statement
Assignment operator =
Data type of variable on left must be compatible with data type on the right
int x = 1;
x = 1;
x = x + 1;

23. public final int EATING = 0;
Constants
A constant is a final variable associated with the class rather than with its instances
final – declare a variable that has a value that never changes; must be initialized; named using uppercase by convention
public final int EATING = 0;

24. Object Instantiation Define objects (classes)
To use the object it must be instantiated or invoked
We will do this in the main( ) method
Object instantiation is an example of a reference variable
Lab1 x; // reference variable declared
x = new Lab1( ); //object instantiated
x.user_interface( ); //method call

25. Naming Conventions
Choose descriptive names with straightforward meanings
First word lowercase and capitalize first letter of subsequent words
showInputDialog
Capitalize first letter of class name
ComputeArea

26. Proper Indentation & Spacing
Consistent indentation style makes programs clear & easy to read, debug, and maintain
int i= 3+4 * 4;
int i = * 4;
Bad style
Good style

27. Block Style Next-line style End-of-line style – Java API standard
Both are acceptable; pick one and stick with it

28. Testing and Debugging Syntax Errors Run-Time Errors Logic Errors
Error messages from the compiler
Fatal or Warnings
Run-Time Errors
Cause the program to terminate abnormally
Logic Errors
Mistakes in algorithm used to solve problem

29. Homework 1

30. Numeric Operations Precedence Order Operator Operation 1 ( )
Parentheses 2
* / %
Multiplication, Division, Modulus 3
+ -
Addition, Subtraction

31. Numeric Operations
* 6
(4 + 5) * 6
4 + 5 % 3
9 % 2 * 7 / 3

32. Increment & Decrement Operators
When used in isolation, K++ is the same as ++K
int k;
k = k + 1;

33. Increment & Decrement Operators
Expression
Operation
Interpretation
j = ++k
Preincrement
k = k + 1
j = k
j = k++
Postincrement
j = - -k
Predecrement
k = k - 1
j = k - -
Postdecrement

34. Shorthand Operators += i += 8 i = i + 8 -= i -= 8 i = i – 8 *= i *= 8
Name
Example
Equivalent +=
Addition assignment
i += 8
i = i + 8 -=
Subtraction assignment
i -= 8
i = i – 8 *=
Multiplication assignment
i *= 8
i = i * 8 /=
Division assignment
i /= 8
i = i / 8 %=
Remainder assignment
i %= 8
i = i % 8
CAUTION: There are no spaces in the shorthand operators.

35. Character Data
Java supports Unicode character set enables characters in a wide variety of languages
ASCII character set is 7-bit code, defines 0 to 127 for the letter, digits, and special characters
First 128 characters of Unicode match ASCII character set, making them backward compatible

36. Character Data
Cast operation such as int to convert one type of data to another type
char ch = ‘a’;
System.out.println( ch); //displays a
System.out.println( (int)’a’); //displays 97

37. Escape Sequences System.out.println(“He said “Jave is fun””);
Syntax error from second quotation character.
Overcome this by using Escape Sequence characters.
System.out.println(“He said \“Jave is fun\””);
He said “Java is fun”

38. Character Escape Sequence
Escape Sequences
Character Escape Sequence
Name \b
Backspace \t
Tab \n
Linefeed \f
Formfeed \r
Carriage Return \\
Backslash \’
Single Quote \”
Double Quote

39. Format Output java.text.NumberFormat class
Represent numbers as dollar amounts, percentages, and other formats
import java.text.NumberFormat;
NumberFormat dollars = NumberFormat.getCurrencyInstance( );
System.out.println(dollars.format( ));
$5,129.95

40. Format Output import java.text.NumberFormat;
NumberFormat percent = NumberFormat.getPercentInstance( );
percent.setMaximumFractionDigits(2);
System.out.print(percent.format( rate / 100.0);

41. Format Output java.text.DecimalFormat class
Specify the number of decimal places to display
import java.text.DecimalFormat;
DecimalFormat threeDigits = new DecimalFormat(“0.000”);
System.out.println( threeDigits.format (number));

42. Format Output
print( ) and println( ) cannot directly format certain outputs
Default output of floating-point numbers is typically up to 6 decimal place & 15 decimal places for double
Align output in certain columns
Use printf( ) method

43. Format Output
System.out.printf(formatSting, argumentList);
formatString = string specifying the format of the output
argumentList = list of arguments that are constant values, variables, or expressions; multiple arguments separated with commas

44. Format Output Specifier Output Example %b a Boolean value
true or false %c
a character
‘a’ %d
a decimal integer
200 %f
a floating-point number %e
a number in standard scientific notation
e+01 %s
a string
“Java is cool”

45. Format Output int count = 5 double amount = 45.56
System.out.printf(“count is %d and amount is %f” , count, amount);
count is 5 and amount is
Pg. 96, Table 3.9 for examples

46. Flow of Control

47. Control Structures Sequence: one after the other
Selection: selects a path based upon action
Iteration: repetition

48. Selection Simple if Statement Nested if / else Multiway Statement
switch Statement
Alternative way to write a multiway selection structure
Involves a test of equality
Logical expression being tested must be a primitive integral type byte, short, int, char, long, or boolean

49. boolean Data Type
Java provides six comparison operators to use when comparing two values
Operator
Name
Example
Result
<
less than
radius < 0
false
<=
less than or equal to
radius <= 0
>
greater than
radius > 0
true
>=
greater than or equal to
radius >= 0 ==
equal to
radius == 0 !=
not equal to
radius != 0

50. boolean Data Type
You can compare characters; however comparison is to ASCII character sets
Equality comparison operator is two equal signs == not a single equal sign used for assignment statement
Result of comparison is a boolean value: true or false

51. Boolean Operations Four basic Boolean operations AND (&&) OR (||)
EXCLUSIVE-OR (^)
Differs from OR (||) in that it is true when either O1 and O2 are true, but it is false when both O1 and O2 are true
NOT (!)

52. Boolean Operations Precedence Order Operator Operation 1 ( )
Parentheses 2 !
NOT 3 ^
EXCLUSIVE-OR 4
&&
AND 5 || OR

53. Boolean Operations true || true && false true ^ false && false
true && true && false && false
(!false ^ true) && (true ^ !false)

54. One-Way if Statements
if statement executes an action if and only if the condition is true.
if (radius >= 0) {
area = radius * radius * PI;
System.out.println(“The area for the circle of radius “ radius + “ is “ + area); }
Braces may be omitted if they enclose a single statement.

55. Two-Way if Statement
if statement specifies different actions based on whether the condition is true or false
if (number % 2 == 0)
System.out.println(number + “ is even.”);
else
System.out.println(number + “ is odd.”);

56. Common Errors in Selection
Forgetting necessary braces
Semicolon at end of if line
Redundant testing of boolean values
Dangling else ambiguity

57. Dialog Boxes

58. Dialog Boxes for Input / Output
Use a graphical user interface (GUI) to gather input and display output
Class JOptionPane contained in javax.swing package
showInputDialog – user input from a keyboard
showMessageDialog – display results

59. Dialog Boxes for Input / Output
showInputDialog
string inputString;
inputString = JOptionPane.showInputDialog(“What’s your name?”);
Input from keyboard is always a string
Numbers have to be converted using
Double.parseDouble(inputString)
Integer.parseInt(inputString)

60. Dialog Boxes for Input / Output
showMessageDialog
JOptionPane.showMessageDialog( parentComponent, messageStringExpression, boxTitleString, messageType);
JOptionPane.showMessageDialog( null, “Hello IST 311”, “Greeting”, JOptionPane.INFORMATION_MESSAGE);

61. Dialog Boxes for Input / Output
Parameter
Description
parentComponent
Null, uses a default component that causes the dialog box to appear in the middle of the screen.
messageStringExpression
String that appears in the dialog box
boxTitleString
The title of the dialog box
messageType
Represents the type of icon that will appear in the dialog box

62. Dialog Boxes for Input / Output
messageType
Description
JOptionPane.ERROR_MESSAGE
Error icon is displayed
JOptionPane.INFORMATION_MESSAGE
Information icon is displayed
JOptionPane.PLAIN_MESSAGE
No icon in dialog box
JOptionPane.QUESTION_MESSAGE
Question icon (question mark) displayed
JOptionPane.WARNING_MESSAGE
Warning icon (exclamation point)

63. Dialog Boxes for Input / Output
System.exit( 0 );
Use input / output dialog boxes and properly terminate a program

64. Math Class
java.lang.Math class provides common mathematical functions like:
double pow (double x, double y)
double random( )
long round (double x)
double sqrt (double x)
All Math methods are static class methods and are invoked through the class name
answer = Math.sqrt(9.0);
Included implicitly in all Java programs

65. Generate Random Numbers
Math.random( ) – used to generate random value from 0 to 1 (0 to )
Given the same seed value, Math.random( ) will generate the same sequence of numbers every time.
Number generated is type double
Use a scaling factor to establish the range of numbers to be generated