Data Types, Variables, and Operators

Java Fundamentals (Java SE 8)
Data, Variables, and Operators
Presented by :
Eng Marwa Ali Eissa
;)
2

LOGOkeywords
Keywords are words that :
 Are reserved for use by Java.
 May not be used to name Java applications or objects ,such as
classes ,methods or variables.
 Are case-sensitive and in lowercase

LOGOIdentifiers
An identifier is a name that:
 Identifies a variable, class or method
 Identifiers must start with either an uppercase or lowercase letter,
an underscore (_), or a dollar sign ($).
 Identifiers cannot contain punctuation, spaces, dashes,
or any of the Java technology keywords.
 Most importantly identifiers are case sensitive.
 Identifiers cannot begin with a digit (0-9)
 White space is not permitted.
 Examples of legal identifiers: age, $salary, _value, __1_value
 Examples of illegal identifiers : 123abc, -salary , max value

LOGONaming Convention in Java
 packages names are in lowercase .
E.g :java.lang,java.util and com.ourglobalcompany.myproject.model
 Classes: Names should be in CamelCase is where each new word
begins with a capital letter
E.g. :CustomerAccount , Employee
 Methods & Variables : is the same as CamelCase except the first letter
of the name is in lowercase
E.g.: firstName ,orderNumber
void calculateTax() , String getSalary()
 Constants: Names should be in uppercase.
E.g.: DEFAULT_WIDTH , MAX_HEIGHT

LOGOStatements and Blocks
Statements are roughly equivalent to sentences in natural languages.
A statement forms a complete unit of execution. The following types of
expressions can be made into a statement by terminating the
expression with a semicolon (;).
 Assignment expressions
 Any use of ++ or --
 Method invocations
 Object creation expressions

LOGOStatements and Blocks
Multiple Java statements may be grouped using braces to form a block
statement. Block statements are logical units of statements ,usually
associated with a specific statement container such as a method or a
loop .Java allows to place a block statement within another block

LOGOVariables
Variables are named memory locations that are used for storing data
items of a value of a particular data type or a reference to an object.
 Variable lives confined to the scope of their definition, which cab be :
 At the local evlevel inside a method or block of code , they are called
local variables
 At the object instance lel when defined as a Non-static attribute
, also called instance variables
 At the class level when defined as a static attribute , also called
class variables
Variables in method declarations—these are called parameters.

LOGOVariables
Variable Naming Conventions
The variable naming conversions are the same as those of identifiers
Java developers must not use the dollar symbol in a variable. Also, variable
names must not start with an underscore
Initializing Variables
You can assign values to variables in your program during variable declaration.
datatype variableName = initvalue;
datatype variable1 = initvalue , variable2= initvalue2 , .... , variableN= initvalueN;
Uninitialized Variables
Attributes (instance or static) are always initialized to a default value
local variable must be initialized otherwise the Program does not compile
Variable Declaration
 To declare a variable, you use the syntax :
datatype varableName;
 To Declare multiple variables using A single statement :
datatype variable1,variable2 ,variable3 ,..... variableN;

LOGO
9
Data Types in JAVA
 Value Types (Built in data types – Primitive data types Like: int ,
float , ..)
 Reference Types (any other type Like: objects , Interface ,
array, Enum ..)
5
x
int x =5;
stack heap
Memory
ref
Data

LOGOPrimitive Data Types
s There are eight primitive data types supported by Java,
and they enable you to define variables for storing data that
fall into one of three categories:
1. Numeric values
 integer (byte, short, int, and long)
 floating-point (float and double)
2. A single Unicode character (char)
3. Logical values (boolean) that can be true or false

LOGOInteger Data Types
Data Type Size Range Default
Value
byte 1 byte (8 bits) -27 to 27-1 (-128 to +127 or 256 possible
values)
0
short 2 bytes (16 bits) -215 to 215-1 (-32,768 to 32,767 or
65,535 possible values )
0
int 4 bytes (32 bits) -231 to 231-1 (-2,147,483,648 to
2,147,483,647 or 4,294,967,296 possible
Values )
0
long 8 bytes (64 bits) -263 to 263-1 (-
9,223,372,036854,775,808 to
9,223,372,036854,775,807, or
18,446,744,073,709,551,616
possible values)
0L

LOGOFloating-Point Data Types
Data Type Size Default Value
float 32-bit 0.0f
double 64-bit 0.0d
 Float is mainly used to save memory in large arrays of floating
point numbers.
 Float data type is never used for precise values such as
currency.
 Double data type is generally used as the default data type for
decimal values. generally the default choice.
 Double data type should never be used for precise values such
as currency.

LOGOCharacter Type
 Char data type is used to store any character.
 Java uses Unicode to represent characters
 char data type is a single 16-bit Unicode character.
 Minimum value is 'u0000' (or 0).
 Maximum value is 'uffff' (or 65,535 inclusive).
 Default value : 'u0000'
 Example : char letterA ='A'

LOGOBoolean Type
 boolean data type represents one bit of information.
 There are only two possible values : true and false.
 This data type is used for simple flags that track true/false
conditions.
 Used to hold the result of an expression that evaluates
to either true or false.
 Default value : false
 The size of boolean is not defined in the Java specification, but
requires at least one bit.
 Example : boolean one = true

LOGOPrimitive Casting
byte  short int long float double
Implicit Casting
Explicit Casting
(Automatic Type Conversions)
Explicit casting
Implicit casting
Data loss due to
explicit down casting

LOGOLiterals
A literal in java is any item that directly represents a particular value .
Variables belonging to any primitive types can also be assigned values
and treated as literals .
Each variable type has a corresponding literal type , such as integer,
character, string and boolean
Literal

LOGOTypes of Literals
There are four types of literals in java, which are based on the
types of variables present
 Numeric Literal
 int  ex: 7
 double  ex: 12.87 , 12e22 , 19E-95
 float  ex: 12.87f , 123.988F
 Boolean Literal
 true or false
 Character Literal
 ‘a’ ,’A’,’#’,’3’  ASCII
 String Literal
 “hi from Marwa” , “Welcome n in New Horizons”

LOGOEscape Sequences for Character Literals
Escape Sequence Description
t Insert a tab in the text at this point.
b Insert a backspace in the text at this point.
n Insert a newline in the text at this point.
r Insert a carriage return in the text at this point.
f Insert a formfeed in the text at this point.
'
Insert a single quote character in the text at
this point.
"
Insert a double quote character in the text at
this point.

Insert a backslash character in the text at this
point.
d Octal
xd Hexadecimal
ud Unicode Character

LOGODeclaring Constants
 A Constant is a variable type in java whose value does not
change .
 Constants are defined using the final keyword followed by the
variable declaration. By convention ,constant variable names
are in uppercase .If the name is composed of more than one
word, the words are separated by an underscore (_).
 Constants defined in this way cannot be reassigned, and it is
a compile - time error if your program tries to do so.
EX: final double PI=3.141592653589793;
EX: final int FEET_PER_YARD = 3;

LOGOExpressions
An expression is a combination of operators (such as
addition '+', subtraction '-', multiplication '*', division '/')
and operands (variables or literals), that can be evaluated
to yield a single value of a certain type
1 + 2 * 3 // evaluated to int 7
int sum, number; sum + number // evaluated to an int value
// Evaluated to a double value
double principal, interestRate; principal * (1 + interestRate)

LOGOOperators
 Arithmetic Operators
 Assignment Operators
 Relational Operators
 Logical Operators
 Increment and Decrement Operators
 Bitwise Operators
 Operator Precedence

LOGOArithmetic Operators
Operator Meaning Syntax
+ Addition X + y
‫ــ‬ Subtraction X - y
* Multiplication X * y
/ Division X / y
% Modulus
The reminder from a division
operation
X % y
Arithmetic operators are used in mathematical expressions
String Concatenation
The + operator may used to concatenate the strings together
System.out.println("Account Balance is"+ balance);

LOGOCompound Arithmetic Assignment Operators
Operator Expression Meaning
+= X += y X=X + y
‫=ــ‬ X -= y X=X – y
*= X *= y X=X * y
/= X /= y X=X / y
%= X %= y X=X % y
= Simple assignment operator, Assigns values from right side
operands to left side operand

LOGORelational Operators
Relational Operators are symbols user for determining
relational comparisons between operands. all expressions
created using relational operators will return a boolean value
, depending on whether the comparison is true
Operator Meaning Syntax
== equal to X == y
!= not equal to X != y
> greater than X > y
< less than X < y
>= greater than or equal to X >= y
<= less than or equal to X <= y

LOGOLogical Operators
Operator Meaning
& logical AND
&& conditional AND
| logical OR
|| Conditional OR
^ exclusive OR (XOR)
! logical (NOT)
Logical Operators evaluate expressions that carry boolean
values . The result returned by logical operators is also a
boolean value.

LOGOLogical Operators - The truth tables

LOGOIncrement and Decrement Operators
Operator Meaning
++ Increment operator; increase the
value of a numeric variable or array
element by 1
-- Decrement operator; reduce the
value of a numeric variable or array
element by 1
Prefix and Postfix
 Prefix :
Placing the operator before the operand causes increment or decrement to
occur before the value of the operand is used to evaluate an expression
For example : int a=5;
int x =++a;
both x and a will have the value 6
 Postfix :
Placing the operator after the operand causes increment or decrement to
occur after the value of the operand is used in an expression
For example : int a=5;
int x =a++;
x will have the value of 5 and a will have the value 6

LOGOBitwise Operators
Operator Description
Binary bitwise AND (&) Returns a 1 if both bits are 1
Binary bitwise OR (|) Returns a 1 if either bit is 1
Binary bitwise XOR (^) Returns a 1 if both bits have different values
Unary bitwise complement (~) Changes each bit in its operand to the
opposite value
Binary left shift (<<) Shifts bits on the left to the left by a
distance denoted by the right operand .Fills
in zeros
Binary right shift (>>) Shifts bits on the left to the right by a
in the highest bit on the left side.
Binary arithmetic and logical shift
(>>>)
Shifts bits on the left to the right by a
in zeros

LOGO
29
00001010
&
00011001
________
00001000
00001010
|
00011001
________
00011011
00001010
~
________
11110101
X=10
y=25
z=8 z=27 z=-11
00001010
>>
2
________
00000010
z=2
11110101
>>
2
________
11111101
z=-3
X=10 X=-11
00001010
<<
2
________
00101000
z=40
0X ff ff ff ff ff
>>>
42
________
0X 00 00 00 ff
z=255
X=-1
00001010
>>>
2
________
00000010
z=2
X=10
Bitwise Operators

LOGOOperator Precedence
Operator precedence is the order in which operators are
evaluated in an expression containing two or more
operators
Operators with same
precedence are calculated
from left to right
Parentheses alter the
order of calculations

LOGOOperator Precedence
precedence Operator
1 (..) [..] . (dot operator)
2 ++ -- ! ~ instanceof
3 new (type) expression
4 * / %
5 + -
6 << >> >>>
7 < > <= >=
8 = !=
9 &
10 ^
11 |
12 &&
13 ||

Data Types, Variables, and Operators

Data Types, Variables, and Operators

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