1. Fundamentals 2

2. Programs and Data
Most programs require the temporary storage of data. The data to be processed is stored in a temporary storage in the computer's memory: space memory.
A space memory has three characteristics
Identifier
Data Type
State

3. Identifier
is a sequence of characters that denotes the name of the space memory to be used.
This name is unique within a program.
Identifier Rules
It cannot begin with a digit (0 – 9).
It may contain the letters a to z, A to Z, the digits 0 to 9, and the underscore symbol, _.
No spaces or punctuation, except the underscore symbol, _, are allowed. 
Identifiers in Java are case-sensitive. Thus, the identifiers myNumber
and mynumber, are seen as two different identifiers by the compiler.

4. State My be changed  variable Cannot be changed  constant
All lowercase.
Capitalizing the first letter of each word in a multiword identifier, except for the first word.
Cannot be changed  constant
All uppercase, separating words within a multiword identifier with the underscore symbol, _.

5. Data Type
The data type defines what kinds of values a space memory is allowed to store.
All values stored in the same space memory should be of the same data type.
All constants and variables used in a Java program must be defined prior to their use in the program.

6. Java built-in Data Types

7. Primitive Data Types Type Size (bits) Range Description boolean
true, false
Stores a value that is either
true or false.
char 16
0 to 65535
Stores a single 16-bit Unicode character.
byte 8
-128 to +127
Stores an integer.
short to
int
32 bits
-2,147,483,648 to
+2,147,483,647
long
64 bits
-9,223,372,036,854,775,808 to
+9,223,372,036,854,775,807
float
accurate to 8 significant digits
Stores a single-precision
floating point number.
double
accurate to 16 significant digits
Stores a double-precision

8. Variable/Constant Declaration
When the declaration is made, memory space is allocated to store the values of the declared variable or constant.
The declaration of a variable means allocating a space memory which state (value) may change.
The declaration of a constant means allocating a space memory which state (value) cannot change.

9. Constant Declaration
final dataType constIdentifier = literal | expression;
final int MAX = 1024;
final int MIN = 128;
final int AVG = (MAX + MIN) / 2;
These are called literals.
This is called expression.

10. Variable Declaration A variable may be declared: With initial value.
Without initial value.
Variable declaration with initial value;
dataType variableIdentifier = literal | expression;
double avg = 0.0; int i = 1;
int x =5, y = 7, z = (x+y)*3;
Variable declaration without initial value;
dataType variableIdentifier;
double avg; int i;

11. More declaration examples
String declaration
with initial value:
String word="Apple";
without initial value:
String word;
char declaration
char symbol ='*';
char symbol;
Boolean declaration:
with initial value:
boolean flag=false;
boolean valid=true;
without initial value:
boolean flag;

12. Exercises Student name 1course course*name
A-Declare a variable of double type with initial value=0.0;
B- Declare a constant of String type with initial value=“Good”
C- Declare a variable of type string with initial value equals to the value of constant in B.
D-Is the following names are valid , why?
Student name
1course
course*name

13. Dr. S. GANNOUNI & Dr. A. TOUIR
Operators
Operators are special symbols used for:
mathematical functions
assignment statements
logical comparisons
Examples of operators:
// uses + operator
– 4 * (5 – 3) // uses +, -, * operators
Expressions: can be combinations of variables and operators that result in a value
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

14. Dr. S. GANNOUNI & Dr. A. TOUIR
Groups of Operators
There are 5 different groups of operators:
Arithmetic Operators
Assignment Operator
Increment / Decrement Operators
Relational Operators
Logical Operators
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

15. Java Arithmetic Operators
Addition +
Subtraction –
Multiplication 
Division /
Remainder (modulus ) %
Assignment Operator =
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

16. Dr. S. GANNOUNI & Dr. A. TOUIR
Arithmetic Operators
The following table summarizes the arithmetic operators available in Java.
This is an integer division where the fractional part is truncated.
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

17. Dr. S. GANNOUNI & Dr. A. TOUIR
Example
Example of division issues:
10 / 3 gives 3
10.0 / 3 gives
As we can see,
if we divide two integers we get an integer result.
if one or both operands is a floating-point value we get a floating-point result.
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

18. Dr. S. GANNOUNI & Dr. A. TOUIR
Modulus
Generates the remainder when you divide two integer values.
5%3 gives 2 5%4 gives 1
5%5 gives 0 5%10 gives 5
Modulus operator is most commonly used with integer operands. If we attempt to use the modulus operator on floating-point values we will garbage!
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

19. Example: Sum of two integer
public class Sum {
// main method
public static void main( String args[] ){
int a, b, sum;
a = 20;
b = 10;
sum = a + b;
System.out.println(a + ” + ” + b + “ = “ + sum);
} // end main
} // end class Sum
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

20. Arithmetic/Assignment Operators
Java allows combining arithmetic and assignment operators into a single operator:
Addition/assignment +=
Subtraction/assignment =
Multiplication/assignment =
Division/assignment /=
Remainder/assignment %=
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

21. Increment/Decrement Operators
Only use ++ or   when a variable is being incremented/decremented as a statement by itself.
x++; is equivalent to x = x+1;
x--; is equivalent to x = x-1;
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

22. Dr. S. GANNOUNI & Dr. A. TOUIR
Relational Operators
Relational operators compare two values
They Produce a boolean value (true or false) depending on the relationship
Operation
Is true when
a >b
a is greater than b
a >=b
a is greater than or equal to b
a ==b
a is equal to b
a !=b
a is not equal to b
a <=b
a is less than or equal to b
a <b
a is less than b
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

23. Dr. S. GANNOUNI & Dr. A. TOUIR
Example
int x = 3;
int y = 5;
boolean result;
result = (x > y);
now result is assigned the value false because 3 is not greater than 5
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

24. Dr. S. GANNOUNI & Dr. A. TOUIR
Logical Operators
Symbol Name
&& AND
|| OR
! NOT
&& T F || T F
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

25. Dr. S. GANNOUNI & Dr. A. TOUIR
Example
boolean x = true; boolean y = false; boolean result; result = (x && y); result is assigned the value false result = ((x || y) && x); (x || y) evaluates to true (true && x) evaluates to true result is then assigned the value true
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

26. Dr. S. GANNOUNI & Dr. A. TOUIR
Operators Precedence
Parentheses
(), inside-out
Increment/decrement
++, --, from left to right
Multiplicative
*, /, %, from left to right
Additive
+, -, from left to right
Relational
<, >, <=, >=, from left to right
Equality
==, !=, from left to right
Logical AND
&&
Logical OR ||
Assignment
=, +=, -=, *=, /=, %=
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

27. Standard Output Window
Using System.out, we can output multiple lines of text to the standard output window.
The exact style of standard output window depends on the Java tool you use.
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

28. Dr. S. GANNOUNI & Dr. A. TOUIR
The println Method
We use println instead of print to skip a line.
int x = 123, y = x + x;
System.out.print( " x = “ );
System.out.println( x );
System.out.print( " x + x = “ );
System.out.println( y );
System.out.println( " THE END“ );
x = 123
x + x = 246
THE END
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

29. Dr. S. GANNOUNI & Dr. A. TOUIR
Standard Input
To input primitive data values, we use the Scanner class.
4 steps are needed to be able to use input primitive:
Step 1: import the Scanner class:
import Java.util.Scanner;
Step 2 : declaring a reference variable of a Scanner
Scanner read ; //we named the object read
Step 3: creating an instance of the Scanner
read = new Scanner (System.in);
Step 4: use specific methods to enter data
int x = read.nextInt();
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

30. Dr. S. GANNOUNI & Dr. A. TOUIR
Example
import java.util.Scanner;
public class TestInput {
public static void main(String[] args) {
Scanner input ;
int area ,length, width;
input = new Scanner (System.in); // creating an instance
System.out.println("enter the length ");
length = input.nextInt(); //reading the length from the keyboard
System.out.println("Enter the Width ");
width = input.nextInt(); //reading the width from the keyboard
area = length * width ;
System.out.println("the length is "+ length);
System.out.println("the width is "+ width);
System.out.println("the area is "+ area); }
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

31. Dr. S. GANNOUNI & Dr. A. TOUIR
Output
enter the length 2 Enter the Width 3 the length is 2 the width is 3 the area is 6
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR

32. Common Scanner Methods
Method Example
Scanner input = new Scanner (System.in);
nextByte( ) byte b = input.nextByte( );
nextDouble( ) double d = input.nextDouble( );
nextFloat( ) float f = input.nextFloat( );
nextInt( ) int i = input.nextInt( );
nextLong( ) long l = input.nextLong( );
nextShort( ) short s = input.nextShort( );
next() String str = input.next();
Introduction to OOP
Dr. S. GANNOUNI & Dr. A. TOUIR