The document discusses Java data types including their default values, sizes, and ranges. It covers primitive data types like boolean, char, byte, short, int, long, float, and double. For each type it provides the default value, size in bytes, and possible value ranges. The document also discusses type conversion between data types, both implicit and explicit conversion. It provides examples of valid variable names in Java and rules for naming variables.

2. Datatypes

3. Datatypes
Data Type Default Value Default size
boolean false 1 bit
char 'u0000' 2 byte
byte 0 1 byte
short 0 2 byte
int 0 4 byte
long 0L 8 byte
float 0.0f 4 byte
double 0.0d 8 byte

4. Datatypes
Type Size in Bytes Range
byte 1 byte -128 to 127
short 2 bytes -32,768 to 32,767
int 4 bytes -2,147,483,648 to 2,147,483, 647
long 8 bytes -9,223,372,036,854,775,808 to
9,223,372,036,854,775,807
float 4 bytes Approximately ±3.40282347E+38F
(6-7 significant decimal digits)
Java implements IEEE 754 standard
double 8 bytes approximately ±1.79769313486231570E+308
(15 significant decimal digits)
char 2 byte 0 to 65,536 (unsigned)
boolean not precisely
defined*
true or false

5. int a;
1000
10
a
Variable Declaration:
Variable Initialization: a = 10;
int:
4 bytes
Can take both positive & negative integers
Datatypes

6. float b;
2000
10.456f
b
Variable Declaration:
Variable Initialization: b = 10.456f;
float:
4 bytes
Can take both positive & negative integers
Datatypes

7. float:
4 bytes
Precision 6 decimal places
Can take both positive &
negative integers
double:
8 bytes
Precision 15 decimal places
Can take both positive &
negative integers
Float vs Double

8. char a = ‘s’ // alphabets
char a = ‘?’ // special symbols
char a = ‘3’ // numeric
Datatypes
char :
2 bytes
S, ? and 3 - anything in single quotes is stored as
an character

10.  Byte -> Short -> Int -> Float -> Double
 Byte -> short -> int -> long
Example:
int a = 10;
float = a + 10;
Type Conversion(Implicit conversion)

11. Type Conversion(Explicit conversion
Double -> Float -> Long -> Int -> Short -> Byte
Example:
double d = 10;
int a = d + 10;
Error:
How will you solve?

12. Type Conversion(Explicit conversion)
int -> char
Example:
char ch = ‘a’;
ch = ch - 32;
Error:
How will you solve?

13. Type Conversion(Explicit conversion
Double -> Float -> Long -> Int -> Short -> Byte
Example:
double d = 10;
int a = d + 10;
 Not possible by the compiler to convert automatically.
 Down conversion is not possible.
 Programmer has to do conversion code in program.

14. Type Conversion(Explicit conversion
Double -> Float -> Long -> Int -> Short -> Byte
Example:
double d = 10;
int a = d + 10;
Syntax for conversion :
target_variable =(target_datatype)source_variable
int a=( int ) d +10

15. Variables
Variable is a container which is used to store some form of values
Variable declaration:
Data_type variable_name
E.g: int sum; float salary; char ch;

16. • NUMBER
• _num
• 93num
• num93
• first.name
• first_name
• last nam
• nUMBER
• mid.name
• 4321
Valid Variable names

17. int num;
int NUM;
int Num ;
num, Num, NUM - all three are
different variable names.
Rules:
1. Lower case
2. Upper case
3. Lower and Upper case
C Language is case sensitive
Variable name:
Variables

18. int _num;
int num_;
int Num_ber ;
int Num.ber ;
int Num ber ;
1. Underscore can be placed
anywhere
2. Except Underscore no other special
characters are allowed
(like dot, white space, etc.,)
Variables
Rules:
Variable name:

19. int 9num;
int num9;
int Num_7_is ;
int float;
1. First character should be
alphabet or underscore
2. Digits 0 – 9 are allowed
3. Variable name should not be a
keyword
Variables
Rules:
Variable name:

20. int number=‘A’;
int number=“A”;
int number=2.4 ;
int number=(int)2.4;
Variables
Output:
Variable name:
int number=(int)2.5;
65
Compiler error
Compiler error
2
2
Explanation
Assigning character will store ASCII
value of char to int
String is higher order dataytype than int
Float is higher order datatype than int
Expliict conversion + truncation
happens
Expliict conversion + truncation
happens

21. THANK YOU