Java 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

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

  • The byte data type is an 8-bit signed two's complement integer

  • The minimum value is -128 (-2^7)

  • The maximum value is 127 (inclusive)(2^7 -1)

  • The default value is 0

  • The 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

byte myNum = 100;
System.out.println(myNum);

short

  • The 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)

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

  • The default value is 0.

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

short myNum = 5000;
System.out.println(myNum);

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

int myNum = 100000;
System.out.println(myNum);

long

  • The 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
  • The default value is 0L
  • Example: long a = 100000L, long b = -200000L
long myNum = 15000000000L;
System.out.println(myNum);

float

  • The 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

  • The float data type is never used for precise values such as currency

  • Example: float f1 = 234.5f

float myNum = 5.75f;
System.out.println(myNum);

double

  • the 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

  • The double data type should never be used for precise values such as currency

  • Default value is 0.0d

  • Example: double d1 = 123.4

double myNum = 19.99d;
System.out.println(myNum);

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
  • The default value is false
  • Example: boolean one = true
boolean isJavaFun = true;
boolean isFishTasty = false;
System.out.println(isJavaFun);     // Outputs true
System.out.println(isFishTasty);   // Outputs false

char

  • the 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'
char myGrade = 'B';
System.out.println(myGrade);

 

Non-Primitive Data Type

Non-primitive data types are called reference types because they refer to objects.

The main difference between primitive and non-primitive data types are:

  • Primitive types are predefined (already defined) in Java. Non-primitive types are created by the programmer and is not defined by Java (except for String).
  • Non-primitive types can be used to call methods to perform certain operations, while primitive types cannot.
  • A primitive type has always a value, while non-primitive types can be null.
  • A primitive type starts with a lowercase letter, while non-primitive types start with an uppercase letter.
  • The size of a primitive type depends on the data type, while non-primitive types have all the same size.

 

Java Literals

A literal 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 literals. For example −

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

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

Example

"Hello World"
"two\nlines"
"\"This is in quotes\""

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

char a = '\u0001';
String a = "\u0001";

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

Notation Character represented
\n Newline (0x0a)
\r Carriage return (0x0d)
\f Formfeed (0x0c)
\b Backspace (0x08)
\s Space (0x20)
\t tab
\" Double quote
\' Single quote
\\ backslash
\ddd Octal character (ddd)
\uxxxx Hexadecimal UNICODE character (xxxx)