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Java datatypes represent types of variables.
int a = 10
a is a variable of type int
Java datatypes represent the memory size of the variables.
Ex: int is having a memory size of 4 bytes.
Java datatypes represent the range value of the variables.
Ex : Byte can store from [ -128 to 127 ] .
Java data types list
There are 8 primitive datatypes in java: byte, short, int, long, float, double, char, boolean.
byte, short, int, long are used to represent numeric values
float, double is used to represent decimal or floating-point values
char is used to represent a single character
boolean is used to represent true and false
Size of data types in java
byte – 1 byte ( 8 bits )
short – 2 bytes ( 16 bits )
int – 4 bytes ( 32 bits )
long – 4 bytes ( 32 bits )
float – 4 bytes ( 32 bits )
double – 8 bytes ( 64 bits )
char – 2 bytes ( 16 bits )
boolean – No Size [ Contains only 2 constants true or false and their memory is decided by JVM ]
Default values of java datatypes
At the time of declaring a variable if we are not assigning any value then JVM provides some default values to those variables which are known as default values.
Note* JVM provides the default values.
byte – 0
short – 0
int – 0
long – 0
float – 0.0
double – 0.0
char – ‘ ‘ [ Single space ]
boolean – false
Java data types range
byte – [ -128 to 127 ]
short – [ -32,768 to 32,767 ]
int – [ -2,147,483,648 to 2,147,483,647 ]
long – [ -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 ]
float – [ 3.4e−038 to 3.4e+038 ] 4 bytes 7 decimal digits
double – [ 1.7e−308 to 1.7e+308 ] 8 bytes 16 decimal digits
char – [ ‘\u0000’ to ‘\uffff’ ] OR [ 0 to 65,535 ] 16 bit unicode character
Ex : \u0041 – A
Check this link to understand Unicode characters: https://www.alansofficespace.com/unicode/unicd99.htm
Calculating Java data types range
1 ) byte : 8 bits
Formula : (-2^n) to (2^n – 1)
Calculation : n = 8-1 = 7
= -2^7 to 2^7 – 1
= -128 to 127
2 ) short : 16 bits
Formula : (-2^n) to (2^n – 1)
Calculation : n = 16-1 = 15
= -2^15 to 2^15 – 1
= -32,768 to 32,767
3 ) float : 32 bits
= 3.4e−038 to 3.4e+038
= -3.4 * 10^38 to 3.4 * 10^38 [ 7 decimal digits ]
To understand the calculation of floating-point range we need to understand the floating-point arithmetic in a better way. We have to understand the mathematics behind floating points. From a Java developer perspective, we don’t have to go into that depth still if you want to understand it please check the below links.
https://en.wikipedia.org/wiki/Floating-point_arithmetic#Floating-point_numbers
https://stackoverflow.com/questions/8746443/float-and-int-both-4-bytes-how-come/8746839
FAQ
Point values are by default double values. Now if we provide a decimal or floating-point value to a variable then it is considered as a double. But if we have to consider that value as a float then we have to add or suffix the letter f to the value.
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