Java - Basic Datatypes

Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in the memory.

Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the reserved memory. Therefore, by assigning different data types to variables, you can store integers, decimals, or characters in these variables.

There are two data types available in Java −

Primitive Data Types

Reference/Object Data Types

Primitive Data Types

There are eight primitive datatypes supported by Java. Primitive datatypes are predefined by the language and named by a keyword. Let us now look into the eight primitive data types in detail.

byte

Byte data type is an 8-bit signed two s complement integer

Minimum value is -128 (-2^7)

Maximum value is 127 (inclusive)(2^7 -1)

Default value is 0

Byte data type is used to save space in large arrays, mainly in place of integers, since a byte is four times smaller than an integer.

Example: byte a = 100, byte b = -50

short

Short data type is a 16-bit signed two s complement integer

Minimum value is -32,768 (-2^15)

Maximum value is 32,767 (inclusive) (2^15 -1)

Short data type can also be used to save memory as byte data type. A short is 2 times smaller than an integer

Default value is 0.

Example: short s = 10000, short r = -20000

int

Int data type is a 32-bit signed two s complement integer.

Minimum value is - 2,147,483,648 (-2^31)

Maximum value is 2,147,483,647(inclusive) (2^31 -1)

Integer is generally used as the default data type for integral values unless there is a concern about memory.

The default value is 0

Example: int a = 100000, int b = -200000

long

Long data type is a 64-bit signed two s complement integer

Minimum value is -9,223,372,036,854,775,808(-2^63)

Maximum value is 9,223,372,036,854,775,807 (inclusive)(2^63 -1)

This type is used when a wider range than int is needed

Default value is 0L

Example: long a = 100000L, long b = -200000L

float

Float data type is a single-precision 32-bit IEEE 754 floating point

Float is mainly used to save memory in large arrays of floating point numbers

Default value is 0.0f

Float data type is never used for precise values such as currency

Example: float f1 = 234.5f

double

double data type is a double-precision 64-bit IEEE 754 floating point

This 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

Default value is 0.0d

Example: double d1 = 123.4

boolean

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

Default value is false

Example: boolean one = true

char

char data type is a single 16-bit Unicode character

Minimum value is u0000 (or 0)

Maximum value is uffff (or 65,535 inclusive)

Char data type is used to store any character

Example: char letterA = A

Reference Datatypes

Reference variables are created using defined constructors of the classes. They are used to access objects. These variables are declared to be of a specific type that cannot be changed. For example, Employee, Puppy, etc.

Class objects and various type of array variables come under reference datatype.

Default value of any reference variable is null.

A reference variable can be used to refer any object of the declared type or any compatible type.

Example: Animal animal = new Animal("giraffe");

Java Literals

A pteral is a source code representation of a fixed value. They are represented directly in the code without any computation.

Literals can be assigned to any primitive type variable. For example −

byte a = 68;
char a =  A ;

byte, int, long, and short can be expressed in decimal(base 10), hexadecimal(base 16) or octal(base 8) number systems as well.

Prefix 0 is used to indicate octal, and prefix 0x indicates hexadecimal when using these number systems for pterals. For example −

int decimal = 100;
int octal = 0144;
int hexa =  0x64;

String pterals in Java are specified pke they are in most other languages by enclosing a sequence of characters between a pair of double quotes. Examples of string pterals are −

Example

"Hello World"
"two
pnes"
""This is in quotes""

String and char types of pterals can contain any Unicode characters. For example −

char a =  u0001 ;
String a = "u0001";

Java language supports few special escape sequences for String and char pterals as well. They are −

What is Next?

This chapter explained the various data types. The next topic explains different variable types and their usage. This will give you a good understanding on how they can be used in the Java classes, interfaces, etc.