1. COP 2800 Lake Sumter State College Mark Wilson, Instructor
Programming with Java
COP 2800
Lake Sumter State College
Mark Wilson, Instructor

2. Programming with Java
Classes and Objects

3. What is a Class?
A class is a blueprint or prototype from which objects are created.
The term ‘class’ derives from ‘classification’.

4. What is an Object?
An object is a software bundle of related state and behavior. Software objects are often used to model the real-world objects that you find in everyday life.
An object is an instance of a class.
State = Attributes = Instance Variables
Behaviors = Methods

5. UML Representation
What the class knows
What the class does

6. Variables and Constants
Programming with Java
Variables and Constants

7. Variable Types byte – 8 bit integer short – 16 bit integer
int – 32 bit integer
long – 64 bit integer
float – 32 bit floating point
double – 64 bit floating point
boolean – size varies, true or false
char – 16 bit character

8. Variable Names Case sensitive Start with:
Letter (A-Z, a-z),
Underscore (_),
Dollar sign ($)
Subsequent characters may include digits (0-9)
Not a keyword
Styles
Lower case – averagescore
Camel case – averageScore
Underscore – average_score
All caps – PI, reserve for constants
Initial caps – AverageScore, reserve for methods

9. Variable Scope public - the field is accessible from all classes.
private - the field is accessible only within its own class.
Variables declared within a block are only available within that block

10. Constants Only meaningful at the class level
Must be either primitive values or immutable objects
Declared as:
public static final type VARIABLE_NAME = value;
private static final type VARIABLE_NAME = value;

11. Programming with Java
Expressions

12. Operators Postfix: expr++ expr-- Unary: ++expr --expr +expr -expr ~ !
Multiplicative: * / %
Additive: + -
Shift: << >> >>>
Relational: < > <= >= instanceof
Equality: == !=
Bitwise AND: &
Bitwise exclusive OR: ^
Bitwise inclusive OR: |
Logical AND: &&
Logical OR: ||
Ternary: ? :
Assignment: = += -= *= /= %= &= ^= |= <<= >>= >>>=

13. Expression
A construct made up of variables, operators, and method invocations, which are constructed according to the syntax of the language, that evaluates to a single value.
int cadence = 0;
anArray[0] = 100;
System.out.println("Element 1 at index 0: " + anArray[0]);
int result = 1 + 2;
// result is now 3
if (value1 == value2)
System.out.println("value1 == value2");
Force precedent with parentheses:
x + y / 100 // ambiguous
(x + y) / 100 // unambiguous, recommended

14. Statement
Statements are roughly equivalent to sentences in natural languages.
A statement forms a complete unit of execution.
Ends with a semicolon (;)
aValue = ; // assignment statement
aValue++; // increment statement
System.out.println("Hello World!"); // method invocation statement
Bicycle myBike = new Bicycle(); // object creation statement
double aValue = ; // declaration statement

15. Block
A block is a group of zero or more statements between balanced (curly) braces ({}) and can be used anywhere a single statement is allowed.
Can be used to define scope.
Structured construct: Sequence
class BlockDemo {
public static void main(String[] args) {
boolean condition = true;
if (condition) { // begin block 1
System.out.println("Condition is true.");
} // end block one
else { // begin block 2
System.out.println("Condition is false.");
} // end block 2 }

16. Programming with Java
Branching

17. Structured Constructs
Sequence
Branching If
If – Else
Else – If
Switch
Looping
Leading Decision
Trailing Decision
Counting (For)
Enhanced For

18. If Construct Selection control structure with one alternative
Sequence executes if the expression evaluates to true

19. If in Java General if (expression) { one or more statements; }
if (expression) statement;

20. If in Java General if (expression) { one or more statements; }
if (expression) statement;
Examples
if (a == b) {
counter++; }
if (counter > 5) limit = TRUE; // problematic

21. Using If Write Java code that:
Accepts a temperature in degrees Fahrenheit
Converts that temperature to degrees Celsius
Displays the result
Identifies the temperature as hot when it is above 50
Identifies the temperature as cold when it is below 10

22. Using If class TempConvert { public static void main(String[] args) {
int temperatureF;
int temperatureC;
if (args.length > 0) {
try {
temperatureF = Integer.parseInt(args[0]);
} catch (NumberFormatException e) {
System.err.println("Argument" + " must be an integer");
System.exit(1); }
}       /* Convert to Celsius */
temperatureC = int(double(temperatureF – 32) * (5.0 / 9.0));
System.out.format (“%d degrees Fahrenheit is %d degrees Celsius.%n”,
temperatureF, temperatureC); if (temperatureC > 50) {
System.out.println(“Wow that’s hot!”);
} if (temperatureC < 10) {
System.out.println(“Now that’s really chillin’!”);      }      } }

23. If – Else Construct Selection control structure with two alternatives
One sequence executes when the expression evaluates true
Otherwise the other sequence executes

24. If – Else in Java General if (expression) { one or more statements; }

25. If – Else in Java General if (expression) { one or more statements; }
Examples
if (expression) {
one or more statements; }
else {
if (expression) statement;
if (a == b) {
counter++; }
else {
counter--;
if (counter > 5) limit = TRUE;
else limit = FALSE;
if (counter > 5)
limit = TRUE;
else
limit = FALSE;

26. Using If - Else
Write a program to report whether a number entered by user is even or odd

27. Using If - Else class OddOrEven{
public static void main(String[] args) {
int numberToCheck;
if (args.length > 0) {
try {
numberToCheck = Integer.parseInt(args[0]);
} catch (NumberFormatException e) {
System.err.println("Argument" + " must be an integer");
System.exit(1); }
/* checking whether remainder is 0 or not */
if ((numberToCheck % 2) == 0) {
System.out.format("%d is even.%n",numberToCheck);
} else {
System.out.format("%d is odd.%n",numberToCheck);

28. Nested Branches
Any structured construct may contain one or more other structured constructs

29. Nesting Branches
if (x > 0) positives++; if (x < 0) negatives++; if (x == 0) zeros++;
if (x > 0) positives++; else if (x < 0) negatives++; else /* x equals 0 */ zeros++;
if (x > 0) positives++; else if (x < 0) negatives++; else /* x equals 0 */ zeros++;

30. Else – If Construct
Selection control structure with any number of alternatives
Simplified nesting of Ifs

31. Else – If in Java General if (expression) { one or more statements; }
else if (expression) {
else {
if (expression)
statement;
else if (expression)
else

32. Else – If in Java General Example if (expression) { if (a < b) {
one or more statements;
} else if (expression) {
} else { }
if (expression)
statement;
else if (expression)
else
if (a < b) {
lower++;
} else if (a > b) {
higher++;
} else {
same++; }

33. Using Else – If
Write a program that compares two input numbers and reports the result

34. Using Else – If class OddOrEven{
public static void main(String[] args) {
int firstNumber;
int secondNumber;
if (args.length > 1) {
try {
firstNumber = Integer.parseInt(args[0]);
} catch (NumberFormatException e) {
System.err.println("Argument" + " must be an integer");
System.exit(1); }
secondNumber = Integer.parseInt(args[1]);
if (firstNumber == secondNumber) {
System.out.format("Result: %d = %d %n", firstNumber, secondNumber);
} else if (firstNumber > secondNumber)
System.out.format("Result: %d > %d %n", firstNumber, secondNumber);
} else {
System.out.format("Result: %d < %d %n", firstNumber, secondNumber);

35. Using Else – If Revisited
class CompareInts{
public static void main(String[] args) {
int firstNumber;
int secondNumber;
char relation;
if (args.length > 1) {
try {
firstNumber = Integer.parseInt(args[0]);
} catch (NumberFormatException e) {
System.err.println("Argument" + " must be an integer");
System.exit(1); }
secondNumber = Integer.parseInt(args[1]);
if (firstNumber == secondNumber) {
relation = ‘=‘;
} else if (firstNumber > secondNumber) {
relation = ‘>’;
} else {
relation = ‘<‘;
System.out.format("Result: %d %c %d %n", firstNumber, relation, secondNumber);

36. Switch Construct
Selection control structure with any number of alternatives
Works with byte, short, int, long, char, enumerated types, String class, classes that wrap char, byte, short and int.

37. Switch in Java General switch (expression) { case constant:
statements;
break; /* optional */
/* any number of cases */
default: /* optional */ }

38. Switch in Java General Example switch (expression) { case constant:
expressions;
break; /* optional */
/* any number of cases */
default: /* optional */ }
switch (dayOfWeek) {
case ‘Monday’:
daysToWeekend = 5;
break;
case ‘Tuesday’:
daysToWeekend = 4;
case ‘Wednesday’:
daysToWeekend = 3;
case ‘Thursday’:
daysToWeekend = 2;
case ‘Friday’:
daysToWeekend = 1;
default:
daysToWeekend = 0; }

39. Nesting Branches Revisited
daysToWeekend = 0;
if (dayOfWeek == ‘Monday’)
daysToWeekend = 5;
if (dayOfWeek == ‘Tuesday’)
daysToWeekend = 4;
if (dayOfWeek == ‘Wednesday’)
daysToWeekend = 3;
if (dayOfWeek == ‘Thursday’)
daysToWeekend = 2;
if (dayOfWeek == ‘Friday’)
daysToWeekend = 1;
switch (dayOfWeek) {
case ‘Monday’:
daysToWeekend = 5;
break;
case ‘Tuesday’:
daysToWeekend = 4;
case ‘Wednesday’:
daysToWeekend = 3;
case ‘Thursday’:
daysToWeekend = 2;
case ‘Friday’:
daysToWeekend = 1;
default:
daysToWeekend = 0; }
if (dayOfWeek == ‘Monday’)
daysToWeekend = 5;
else if (dayOfWeek == ‘Tuesday’)
daysToWeekend = 4;
else if (dayOfWeek == ‘Wednesday’)
daysToWeekend = 3;
else if (dayOfWeek == ‘Thursday’)
daysToWeekend = 2;
else if (dayOfWeek == ‘Friday’)
daysToWeekend = 1;
else
daysToWeekend = 0;

40. Using Switch
Write a program that accepts two numbers, applies a user provided operator and displays the result as an equation.

41. Using Switch class Calculate{ public static void main(String[] args) {
float firstNumber;
float secondNumber;
char operator;
firstNumber = Float.parseInt(args[0]);
operator = args[1].charAt(0);
secondNumber = Float.parseInt(args[2]);
switch (operator) {
case ‘+’:
System.out.format(
“%.2f + %.2f = %.2f %n”, number1, number2, (number1 + number2));
break;
case ‘-’:
“%.2f - %.2f = %.2f %n”, number1, number2, (number1 - number2));
case ‘*’:
“%.2f * %.2f = %.2f %n”, number1, number2, (number1 * number2));
case ‘/’:
“%.2f / %.2f = %.2f %n”, number1, number2, (number1 / number2));
default:
System.out.format(“%c is not a valid operator.%n”, operator);
System.exit(); }

42. Using Switch Revisited
class Calculate{
public static void main(String[] args) {
float firstNumber;
float secondNumber;
char operator;
float result;
firstNumber = Float.parseInt(args[0]);
operator = args[1].charAt(0);
secondNumber = Float.parseInt(args[2]);
switch (operator) {
case ‘+’:
result = number1 + number2;
break;
case ‘-’:
result = number1 - number2;
case ‘*’:
result = number1 * number2;
case ‘/’:
result = number1 / number2;
default:
printf (“%c is not a valid operator.%n”, operator);
System.exit(); }
system.out.format(“%.2f %c %.2f = %.2f %n”,
number1, operator, number2, result);

43. Branching Summary Keywords Concepts if else else if switch case break
default
Concepts
Branching If
If – Else
Else – If
Switch
Nesting

44. Introduction to Java
Looping

45. Structured Constructs
Sequence
Branching If
If – Else
Else – If
Switch
Looping
Leading Decision
Trailing Decision
Counting (For)
Enhanced For

46. While Construct
Sequence executes as long as the expression evaluates true.
Sequence may never execute.

47. While in Java
General
while (expression) {
statement(s) }

48. While in Java Example General while (count < 11) {
System.out.println(
"Count is: " +
count);
count++; }
while (expression) {
statement(s) }

49. Using While
Write a program that computes the average of an array of integers.

50. Using While class Average{ public static void main(String[] args) {
int sum;
int count;
double average;
int[] numbers = {1,2,3,4,5,6,7,8,9,10};
int i = 0;
while (i < numbers.length) {
sum += numbers[i++];
count++; }
average = double(sum) / double(count);
System.out.println (
“Average of the list is: “ + average);

51. Until Construct
Sequence executes as long as expression evaluates true.
Sequence will always execute at least once.

52. Do – While in Java Example General do { System.out.println(
"Count is: " + count);
count++;
} while (count < 11);
do {
statement(s)
} while (expression)

53. Using Until
Write a program that computes the average of an array of integers.

54. Using Until class Average{ public static void main(String[] args) {
int sum;
int count;
double average;
int[] numbers = {1,2,3,4,5,6,7,8,9,10};
int i = 0;
do {
sum += numbers[i++];
count++;
} while ( i < numbers.length);
average = double(sum) / double(count);
System.out.println (
“Average of the list is: “ + average); }

55. For Construct Special case of While Loop
Responds to a frequent loop form

56. For in Java Example General /* as a while loop */ i = 1;
while (i < 11) {
System.out.println(
"Count is: " + i);
i++ }
/* as a for loop */
for(int i=1; i<11; i++) {
General
for (initialization; termination; increment) {
statement(s) }

57. Using For
Write a program that computes the average of an array of integers.

58. Using For class Average{ public static void main(String[] args) {
int sum;
int count;
double average;
int[] numbers = {1,2,3,4,5,6,7,8,9,10};
for (int i = 0; i < numbers.length; i++) {
sum += numbers[i];
count++; }
average = double(sum) / double(count);
System.out.println (“Average of the list is: “ + average);

59. Enhanced For Works for collections and arrays
Item hold the current value from numbers array
Automatically steps through the list
Example
class EnhancedForDemo {
public static void main(String[] args){
int[] numbers =
{1,2,3,4,5,6,7,8,9,10};
for (int item : numbers) {
System.out.println(
"Count is: " + item); }

60. Using Enhanced For
Write a program that computes the average of an array of integers.

61. Using Enhanced For class Average{
public static void main(String[] args) {
int sum;
int count;
double average;
int[] numbers = {1,2,3,4,5,6,7,8,9,10};
for (int value: numbers) {
sum += value;
count++; }
average = double(sum) / double(count);
System.out.println (“Average of the list is: “ + average);

62. Infinite Loops Expressions in the For Loop are optional
Can be used for infinite loops
While loop is preferred
Example
/* one idiomatic form */
for ( ; ; ) {
statements; }
/* preferred form */
while (true) {

63. Looping Summary Keywords Concepts while do for Leading decisions
Trailing decisions
Counting loops (For)
Enhanced For

64. Programming Assignment
Due 23:59, 20 Jan 2014
Coding Conventions:
File Header
Your name
File name
Assignment name and number
short description or purpose of the program/ object/ code in the file
Describe each function and class. At a minimum, briefly describe the purpose and usage.
Comment obscure or difficult code.