1. Class 7

2. Objectives Identify, declare, and use primitive data types
Use variables in programs to hold data in RAM
Use assignment statements to store data with proper identifiers
Use operators and parentheses correctly in numeric expressions

3. Introduction Data are collections of raw facts or figures
A program performs operations on input data to output information
Input data can come from a variety of sources
The program itself
Users of the program
External files

4. Variables
Variables are like storage locations in the computer’s memory.
Storage for
the value of
the variable

5. Naming Rules of Variables
First character must be one of the letters a-z, A-Z, or an underscore ( _ ) or a $
After first character use a-z, A-Z, 0-9, underscore ( _ ) or $
Any length
Keep them meaningful

6. Variable Rules (con’t)
Case sensitive
ItemsOrder does not equal itemsorder
Cannot declare two variables of the same name in a method
Cannot give a variable the same name as a method

7. Storing Data Java is a strongly typed language
Variables must be declared with a data type
Variable locations can hold only that data type
Java has two categories of data types
Primitive data types hold single data items
Integers, characters, floating point, and booleans are primitive types
Reference data types hold a value that refers to the location of the data
All Objects and arrays are reference types

8. Intrinsic Data Types JAVA has eight intrinsic data
types, which form the basis for all
other data types (i.e., classes):
1. boolean:
- a 1 byte value that is assigned
a value of either true or false
(both are JAVA defined values).
Boolean values have no direct
conversion to integer values,
and are initialized to false.

9. Intrinsic Data Types 2. byte: - a 1 byte integer, capable of
representing numbers from
numbers from -128 to +127.
It is initialized to 0.
3. char:
- a 2 byte integer that is normally
used to represent character values
using the Unicode system (the
first 128 values of which
correspond to ASCII values).
It is initialized to \u0000.

10. Intrinsic Data Types 4. short: - a 2 byte integer, able to represent
numbers between -32K and +32K.
It is initialized to 0.
5. int:
- a 4 byte integer, able to represent
numbers between -2 billion and
+2 billion.

11. Intrinsic Data Types 6. long: - an 8 byte integer, capable of
representing numbers between
-2 and
It is initialized to 0.
7. float:
- a 4 byte IEEE format real number,
giving about 7 decimal digits
of precision.
It is initialized to 0.0f. 63 63

12. Intrinsic Data Types 8. double: - an 8 byte IEEE format real number,
giving about 15 decimal digits
of precision.
It is initialized to 0.0d.

13. Declaring Variables General form: 1. dataType identifier;
2. dataType identifier, identifier, identifier;
3. dataType identifier = initialValue;
4. dataType identifier = new dataType();
int myAge;
int myAge, yourAge, theirAges;
int myAge = 24;
Person me = new Person();

14. Key JAVA Operators ( ) Parenthesis (X+2)/3 Operator Description
Example
( )
Parenthesis
(X+2)/3

15. Key JAVA Operators
Operator
Description
Example *
Multiply
X*2

16. Key JAVA Operators
Operator
Description
Example /
Divide
X/12

17. Key JAVA Operators
Operator
Description
Example %
Modulus
7%3

18. Key JAVA Operators
Operator
Description
Example +
Add
X+7

19. Key JAVA Operators
Operator
Description
Example -
Subtract
X-6

20. Key JAVA Operators = Assignment operator Y=X+3 Operator Description
Example =
Assignment operator
Y=X+3

21. Arithmetic Operators
The order of operator precedence is a predetermined order that defines the sequence in which operators are evaluated in an expression
Addition, subtraction, multiplication, and division can manipulate any numeric data type
When Java performs math on mixed data types, the result is always the larger data type
Casts allow programmers to force a conversion from one primitive type to another

22. Numeric Expressions Numeric expressions evaluate to a number
Only numeric primitive data types may be used in a numeric expression
A value and variable must be separated by an arithmetic operator
Unless parentheses supercede, an expression is evaluated left to right with the following rules of precedence:
Multiplication and/or division
Integer division
Modular division
Addition and/or subtraction

23. Parentheses in Expressions
Parentheses may be used to change the order of operations
The part of the expression within the parentheses is evaluated first
Parentheses can provide clarity in complex expressions
Numeric and conditional expressions should be grouped with parentheses
Parentheses can be nested
Java evaluates the innermost expression first and then moves on to the outermost expression

24. How precedence works x = ( 3 + 8 ) / 3 * 2 + 5 % 3 x = ? 11 / 3
/ 3
* % 3
x = 3
* 2
+ 5 % 3
x = 6
+ 5 % 3
x = 6 + 2
x = 8

25. Assignment Statements
General syntax:
identifier = value;
x = 5;
dataType identifier = value;
int x = 6;
identifier = formula;
x = 3 * y+5;
identifier = differentIdentifier;
x = y;

26. Using Variables in Output to the console instead of to a window
System.out.println(“Hello World”);
System.out.println(5);
System.out.print(“my age is \n“ + age);
System.out.println(“ “);
String concatenation operator

27. Assignment Statements Exercise 1
The value in number is number _
Assignment Statements Exercise 1
int number;
number = 5;
System.out.println(“The value in number is ” “number”) ;
number ? 5

28. Assignment Statements Exercise 2
The value in number is 5 _
Assignment Statements Exercise 2
int number;
number = 5;
System.out.println(“The value in number is ” number) ;
number ? 5

29. Multiple Assignment Statements Tracing Code: exercise 3
int Checking;
int Miles;
long Days;
Checking = -20;
Miles = 4276;
Days = ;
Days ?
187000
Checking ?
Miles ?
-20
4276

30. System.out.println( “We have made a”
+ “ long trip of ” + Miles + “ miles.”);
System.out.print(“Our checking account”
+ “ balance is ”
+ “Checking”);
System.out.print(“\nExactly ” +
Days + “ days ago Columbus”
+ “ stood on this spot.”);
Days
187000
Checking
-20
Miles
4276

31. Multiple Assignment Statements Tracing Code: Exercise 4
double RegWages, BasePay = 18.25;
double RegHours = 40.0;
double OTWages, OTPay = 27.78;
double OTHours = 10;
double TotalWages;
RegWages
?.?
OTWages
?.?
TotalWages
?.?
BasePay
18.25
OTPay
27.78
RegHours
40.0
OTHours 10

32. Basic usage of operators
RegWages = BasePay * RegHours;
OTWages = OTPay * OTHours;
TotalWages = RegWages + OTWages;
System.out.println( “Wages for this”
+ “ week are $ ” +
TotalWages );
RegWages
?.?
OTWages
?.?
730.0
277.8
TotalWages
?.?
BasePay
18.25
OTPay
27.78
RegHours
40.0
OTHours 10
1007.8
PG 66 ~ Pgrm. 2-20

33. Write assignment statements
A) Adds 2 to A and stores the result in B.
B = A + 2;
pg. 85 Problem #20a
a) Adds 2 to A and stores the result in B
b) Multiplies B by 4 and stores the reul in At

34. Write assignment statements
B) Multiplies B times 4 and stores the result in A.
A = B * 4;

35. Write assignment statements
C) Divides A by 3.14 and stores the result in B.
B = A / 3.14;

36. Write assignment statements
D) Subtracts 8 from B and stores the result in A.
A = B - 8;

37. Write assignment statements
E) Stores the value 27 in A.
A = 27;

38. What is this program’s output
int Freeze = 32, Boil = 212;
Freeze = 0;
Boil = 100;
System.out.print(Freeze + “\n “ +
Boil + “\n”);
100 _

39. What is this program’s output
int X = 0, Y = 2;
X = Y * 4;
System.out.println( “” + X + “\n “ +Y ); 8 2 _

40. System.out.print(“I am the incredible” +
“ computing\nmachine ” +
“\nand I will\namaze\n” +
“you.”);

41. I am the incredible computing
machine
and I will
amaze
you. _

42. What is this program’s output
System.out.println( “Be careful\n” +
“This might/n be a trick ” +
“question”);
Be careful
This might/n be a trick question _

43. What is this program’s output
int A, X = 23;
A = X % 2;
System.out.println( X);
System.out.println( A ); 23 1 _

44. Conclusion of Class 7