DATA TYPES IN JAVA

VARIABLE: It is a name given to a memory location, which can hold a value and that can be changed any number of times in future if required.

Advantages: 

Reusability

 Easy to maintain

 Future updations are easy

 NOTE: always use meaningful names.

Syntax: Datatype variablename=value;

Int a=10;

CONSTANT: It is a name given to a memory location, which can hold a value that can’t be changed in future.

Syntax:  final Datatype constantname=value;

Final int a=10;

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 Data Types

Primitive Data Types:

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

Byte: it is used to store an integer value up to 8 bits (-2^7 to 2^7-1).

  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 int.

short: it is used to store an integer value up to 16 bits (-2^15 to 2^15-1).

  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 int

  Default value is 0.

Int: it is used to store an integer value up to 32 bits (-2^31 to 2^31-1).

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

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

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

  The default value is 0.

Long: it is used to store an integer value up to 64 bits (-2^63 to 2^63-1).

  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.

Float  : it is used to store a decimal value up to 32 bits.

  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.

doube : it is used to store a decimal value up to 64 bits.

  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.

Boolean: it is used for storing Boolean values like either TRUE or FALSE.

  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.

Char: it is used for storing a single character.

  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.

Reference Data Types

Reference data types are made by the logical grouping of primitive data types. These are called reference data types because they contain the address of a value rather than the value itself. Arrays, objects, interfaces etc. are examples of reference data types.

• 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 types of array variables come under reference data type.

• Default value of any reference variable is null.

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