Data Type

  • A data type, in programming, is a classification that specifies which type of value a variable has and what type of mathematical, relational or logical operations can be applied to it without causing an error. A string, for example, is a data type that is used to classify text and an integer is a data type used to classify whole numbers.
  • Depending on the datatype,the operating system allocate memory and decides what type of data to be stored EX-a number,a character

There are 2 type of datatype-

Primitive Data Type

Reference Data Type also know as Object Data Type or Non-Primitive

Primitive Data Type-

type of datatype

  • There are 8 primitive data type supported by java.
  • Primitive datatype are predefined by the language and named by a Keyword.
  • Let see the following datatype-

byte-8 bit,and integer type,default value is 0.

short-is integer type and takes 2  bytes,default value is 0.

int-is integer type and takes 4 bytes,default value is 0.

long-is integer type and takes 8 bytes,default value is 0L.

float-is decimal type value,single precision  and takes 4 bytes,default value is 0.0f

char-can store any character and takes 2 bytes,default value is 'u0000'.

double-is decimal type value,double precision and takes 8 bytes,default value is '0.0d'.

boolean-It takes one bytes and can store either of two values;True or False,default value is FALSE.

Primitive data type are those whose variable allows us to store only one value but they never allows us to store multiple value of same type.This is a datatype whose variable can hold maximum one value at a time

Non-Primitive Data type-They are basically defined as derived data types.They are directly or indirectly dependent on primitive data types.The method for storing non-primitive datatype is different from primitive data type.They store the values with reference to the addresses or locations.So,they are also called 'Reference Data type'.






All java component require names.Name used for classes ,method,interface and variable also called identifier.

Identifier follow some rule's which are listed below-

  • All identifiers must start with either a letter(a to z or A to Z) or currency($)character or an underscore.
  • After the first character ,an identifier can have any combination of character.
  • A Java Keyword cannot be used as identifier.
  • Identifier in Java are case sensitive,foo FOO are two different identifier.