Java Variables and Datatypes, primitive data types in java, java data types, java introduction, basic java, java basics

1. Programming in Java
Variable & Data Types
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2. Variable
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name
• Store any type of Value or Data.
• A specific name of Memory region.
• Data type will decide what values will be stored in
variables.
• You can say data type will define the structure of
your data
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3. Data type
a b
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int String
Water- (Value)
Liquid- (Type)
Bottle- (Variable)
• Define the data structure
• Identify type of value/data
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int float
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4. Categories of data type
• Primitive Data type
• Reference Data type/Composite data type
• User Define/Custom Data type
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5. boolean – 1 byte
1. Primitive Data type
Primitive (8)
Numeric (6) Non-Numeric (2)
Integral (4) Floating (2)
char – 2 byte
(Unicode)
float - 4 byte
double – 8 byte
byte - 1 byte
short - 2byte
int - 4byte
long – 8 byte
• It stores value.
• It occupies number of bytes as per data type.
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6. Primitive Data types
• Decimal values will be stored in float and double
data type.
• Non-decimals values will be stored in int, long,
byte and short data types.
• Character will be stored in char data type.
• true/false will be stored in boolean data types.
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7. Primitive Data type detail
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8. 2. Reference/Composite Data
type
Reference/Composite Data
type (3)
String
• It stores memory address of a value.
• It occupies 2 bytes to store a reference (Memory Address).
Array
Object
Ex.
String name = “infovia”
name variable store total size of
value is
address of value “infovia” 14 byte, 2 byte
per it occupies 2
byte. character
i n f ao v i
2 2 2 2 2 2 2
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9. 3. User Defined/Custom data type
User Defined/Custom (2)
• It contains multiple member and member method.
• Size depends on content
class Name {
String firstName;
String middleName;
String lastName;
void printFullName() {
----
}
}
class
enum
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10. Program - Sum of two numbers
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public class Sum {
public static void main(String[] args) {
int firstValue, secondValue, resultOfSum;
firstValue = 25;
secondValue = 15;
resultOfSum = firstValue + secondValue ;
System.out.println(“Sum Result is = ”+ resultOfSum);
}
}
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11. Variable declaration
type variable_name;
Meaning: variable <variable-name> will be a variable of type
<type>
Where type can be:
int //integer
double //real number
Example:
int a, b, c;
double x;
int sum;
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12. Types of Variable ?
Instance/global
Static
local
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13. Program - Division
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public class Division {
public static void main(String[] args) {
float a, b, c;
a = 25.678f;
b = 15;
c = a / b;
System.out.println(“Division Result is = ”+ c);
}
}
/* Output
Division Result is = 1.7118666
if use double data type then result is =
1.7118666330973307
*/
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14. Program - DataTypeExercise
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public class DataTypeExercise {
public static void main(String[] args) {
int i =50;
float f = 25.5f;
double d = 89.789;
boolean b = true;
System.out.print(“ ”+ i + b + f + d)
;
}
}
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15. Constant declaration
Declare variable -
syntax =
type variable_name;
ex. –
double radius = 2.45; // it can be change
Declare Constant -
syntax =
final type constant_name= value;
ex. –
final double PI = 3.1415; // can not be change, now it
fixed
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16. Program –Constant Area of
Circle
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public class AreaOfCircle {
public static void main(String[] args) {
final double PI = 3.1415;
double area;
float radius = 3.5f ;
area = PI* radius * radius ;
System.out.println(“Area of Circle = ”+
area);
}
}
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17. Java Comments
• Single-line comment – it is used to comment only one
line.
• Multi-line comment - it is used to comment multiple
lines of code.
• Document comment – it is used to create documentation
API.
Example :
Single Line Comment –
//This is single line comment
Multi Line Comment
/* This is Multi Line Comment
this is multi line comment */
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18. Identifier
• A name in java program is identifier, which can be
used for identification purpose.
• It can be method name, variable name, class name or
label name.
public class Test{
public static void main(String[] args){
int x = 25;
}
}
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19. Naming convention rules
Rules of defining name (identifier) –
Can use – a to z A to Z 0 to 9 $ _
Identifier -
total_number ok //correct
total# no //can not use symbol
total123 ok //correct
123total no //can not starts with digit
if no //reserve word
ca$h ok //can use, no error, but use at special
case
_$_$_$_$_ ok //can use, no error
all@hands no //can not use symbol
Java2Share ok //correct
Interger ok //can use, no error, but not use because it is
prefined class
Int ok //can use, no error 19
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20. Naming convention rules
class Test{
public static void main(String args[]) {
int number = 10;
int Number = 20; //ok, but use with class (first
character of class name is capital)
int NUMBER =30; //ok, but use with Constant
declaration(All Caps)
int String =78; // ok, no error, but - wrong it is
predefine class
int Runnable = 78; // ok, no error, but - wrong predefine
Interface
} // we can differentiate
with case
} //case sensitive programming
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21. Java Reserved words
• All are written in small letters
false
Reserved
words(53)
Keyword (50)
Reserved literal
(3)
Used (48) Un-used (2) true
goto
const
if, else, for….. Etc.
null
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22. Return type keyword (1) - void
Used Keywords - 48
Keyword for data type (8) - byte, short, int, long, float, double, char,
boolean
Keyword for control statements (11) –
if, else, switch, case, default, while, do, for, break, continue , return
Keyword for exception handling(6) - try, catch, finally, throw, throws, assert
(1.4)
Keywords for access modifier (11) -
private, public, protected, static , final, abstract, synchronized, native,
strictfp (1.2), transient, volatile
Class related keywords (6) - class, interface, extends, implements, package,
import
Object related keywords(4) - new, instanceof, super, this
To define group of named constants (1) – enum (1.5)
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23. Literals
int x = 20;
[Data typevariable constant | literal ]
int x= 10; //decimal value
int x= 010; //octal value -> 8 (octal to
decimal)
int x= 0X10; //hexadecimal value-(base -16)
int x = 10; //ok
int x = 0788; // no CE
int x = 0777 // ok
int x = 0XFace; // ok
int x= 0XBeef; //ok
int x = 0XBeer; //no
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24. Type Specifier
n new line
t horizontal tab
r carriage return
b back space
f form feed
’ single quote
” double quote
back slash
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25. QA
1. Is Java primitive data type stored on stack or heap?
2.What is the default value of local variables in Java?
3.Can you compare a boolean with an int variable in
Java?
4.What is the default value of char data type in Java?
5.What is the output?
System.out.println(1.0/0);
6.Which format is used for char data type in java?
7. Difference between primitive variables and reference
variables?
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26. Get in Touch
Thank You
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