Datatypes

Variable

• A variable is a location in memory (storage area) to hold data.
• To indicate the storage area, each variable should be given a unique name (identifier).
• A variable is a container which holds the value while the Java program is executed. A variable is assigned with a data type.

Data Types

• Data types specify the different sizes and values that can be stored in the variable.
• There are two types of data types in Java:
• Primitive data types: The primitive data types include boolean, char, byte, short, int, long, float and double.
• Non-primitive data types: The non-primitive data types include Classes, Interfaces, and Arrays.

Primitive Data Types

int

• It is used to store whole numbers.
• Size 4 bytes
• Range ( ±2³¹)
• For ex: 4117 , -7463 , 0xA123 , 0277 , 0b01011 etc.

short

• To Store whole numbers
• Size 2 bytes
• Range from -32,768 to 32,767 ( ±2¹⁵)
• For ex: 4117 , -7463 , 0xA123 , 0277 , 0b01011 etc.

long

• To Store whole numbers
• Size 8 bytes
• Range from( ±2⁶³)
• For ex: 41177437722l , 0x6373C12A123L , 0277L , 0b0101100010101L etc.
• Note : long values with suffix l / L

byte

• To Store whole numbers
• Size 1 byte
• Range from -128 to 127( ±2⁷)
• For ex : 27 , 0xA3 , 072

float

• It is used to store floating point values
• Size in memory is 4 bytes
• float has 7 decimal digits of precision.
• Range (1.2e-38 to 3.4e38 )
• For ex: 3.14f , -0.0124f , 2.015fe+003 etc.
• Note: float values with suffix f/F

double

• It is used to store floating point values.
• Size in memory is 8 bytes
• double has 15 decimal digits of precision.
• Range (2.2e-308 to 1.8e308 )
• For ex: 3.140163 , -0.01253424 , 2.015657e+003 etc
• Note: double values with suffix d/D By default values with decimal point are of type double if suffix is not specified.

boolen

• To store Boolean values i.e. true or false.
• Size is 1 bi
• For ex: true , false

char

• To Store a single character.
• Size 8 bytes
• Supports UNICODE char set
• For ex : ‘A’ , ‘a’ , ‘$’ , ’ ‘ etc.

Identifier

• It is a Name which is use to identify different type of programing elements such as Variables , Constants ,Functions….etc

• An identifier must start with alphabets [a to z] [A to Z] or underscore [ _ ].
• Next letters of an identifier can be alphabets [a to z] [A to Z], underscore [ _ ] or digits [0 to 9] .
• Language keywords are no allowed as identifier.
• Max length of identifier can be 31 letters but it can vary depending on different compilers.
• No special symbols [eg. #,$..etc] are allowed. Except [_]

Keywords

• Java keywords are also known as reserved words. Keywords are particular words that act as a key to a code. These are predefined words by Java so they cannot be used as a variable or object name or class name.