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Java Fundamentals

Data types are the means for the tasks related to identifying and assessing the type of data. Java is rich in data types which allows the programmer to select the appropriate type needed to build variables of an application.

Why is the data type important?

  • Every variable in Java has a data type which tells the compiler what type of variable it as and what type of data it is going to store.
  • Data type specifies the size and type of values.
  • Information is stored in computer memory with different data types.
  • Whenever a variable is declared, it becomes necessary to define a data type that what will be the type of data that variable can hold.

Data Types in Java

Data Types available in Java are:
  1. Primary Data Type
    Java supports eight primitive data types: byte, short, int, long, float, double, char and boolean.
    These eight data types are further classified into four groups:
    1. Integer,
    2. Relational Numbers(Floating point)
    3. Characters
    4. Boolean(Conditional).
  2. Non-Primitive Data Types
    Classes, Interface, Arrays, etc.

This chapter is all about basic primitive data types in Java.

Integer Types

Integer is the whole number without any fractional point. It can hold whole numbers such as 196, -52, 4036, etc. Java supports four different types of integers, these are:

Type Contains Default Size Range
byte Signed integer 0 8 bit or
1 byte
-27 to 27-1 or
-128 to 127
short Signed integer 0 16 bit or
2 bytes
-215 to 215-1 or
-32,768 to 32767
int Signed integer 0 32 bit or
4 bytes
-231 to 231-1 or
-2147,483,648 to 2147,483,647
long Signed integer 0 64 bit or
8 bytes
-263 to 263-1 or
-9223,372,036,854,755,808 to 9223,372,036,854,755,807

Rational Numbers

It is used to hold whole numbers containing fractional part such as 36.74, or -23.95 (which are known as floating point constants). There are two types of floating point storage in java. These are:

Type Contains Default Size Range
float IEEE 754 floating point
single-precision
0.0f 32 bit or
4 bytes
±1.4E-45 to
±3.40282347E+38F
double IEEE 754 floating point
double-precision
0.0 64 bit or
8 bytes
±439E-324 to
±1.7976931348623157E+308

Characters

It is used to store character constants in memory. Java provides a character data type called char whose type consumes a size of two bytes but can hold only a single character.

Type Contains Default Size Range
char Unicode character
unsigned
\u0000 16 bits or
2 bytes
0 to 216-1 or
\u0000 to \uFFFF

Conditional

Boolean type is used to test a particular condition during program execution. Boolean variables can take either true or false and is denoted by the keyword boolean and usually consumes one byte of storage.

Type Contains Default Size Range
boolean true or false false 1 bit true or false

Example of Data Types and Variable Declarations in Java

Example:

class DataTypes{
     public static void main(String args[]){
        byte byteVar = 5;
        short shortVar = 20;
        int intVar = 30;
        long longVar = 60;
        float floatVar = 20;
        double doubleVar = 20.123;
        boolean booleanVar = true;
        char charVar ='W';
    
        System.out.println("Value Of byte Variable is " + byteVar);
        System.out.println("Value Of short Variable is " + shortVar);
        System.out.println("Value Of int Variable is " + intVar);
        System.out.println("Value Of long Variable is " + longVar);
        System.out.println("Value Of float Variable is " + floatVar);
        System.out.println("Value Of double Variable is " + doubleVar);
        System.out.println("Value Of boolean Variable is " + booleanVar);
        System.out.println("Value Of char Variable is " + charVar);
     }
 }

Program Output:

Value Of byte Variable is 5
Value Of short Variable is 20
Value Of int Variable is 30
Value Of long Variable is 60
Value Of float Variable is 20.0
Value Of double Variable is 20.123
Value Of boolean Variable is true
Value Of char Variable is W