Java Data Types

Java data types specify the type of value that a variable can store. When you create a variable in Java, you need to tell Java what kind of data the variable will contain.

For example, int age = 25; declares an integer variable named age.

Java data types are mainly divided into two categories:

1. Primitive Data Types
2. Non-Primitive Data Types

Primitive Data Types

Java has 8 primitive data types. They are used to store simple values directly.

Data Type	Size	Example	Used For
byte	8 bits	100	Small whole numbers
short	16 bits	10000	Whole numbers
int	32 bits	50000	Common whole numbers
long	64 bits	5000000000L	Large whole numbers
float	32 bits	10.5f	Decimal values
double	64 bits	10.5	Precise decimal values
char	16 bits	'A'	Single characters
boolean	—	true	True or false values

Integer Data Types

Java provides four types for storing whole numbers: byte, short, int, and long.

The byte type stores small integer values. Its range is -128 to 127.

The short type stores values from -32,768 to 32,767.

The int type is the most commonly used integer type. It can store values from -2,147,483,648 to 2,147,483,647.

The long type is used for very large integer values.

For example:

public class Main {
    public static void main(String[] args) {
        int age = 25;
        long population = 5000000000L;

        System.out.println(age);
        System.out.println(population);
    }
}

Notice the L after the large number. It indicates a long literal.

Floating-Point Data Types

Java provides float and double for storing decimal numbers.

A float uses 32 bits, while a double uses 64 bits and generally provides greater precision.

For example, float price = 99.5f; and double salary = 45000.75;.

double is generally preferred for ordinary decimal calculations.

Character Data Type

The char type is used to store a single UTF-16 code unit.

For example, char grade = 'A';.

Characters are written inside single quotation marks.

public class Main {
    public static void main(String[] args) {
        char grade = 'A';

        System.out.println(grade);
    }
}

Boolean Data Type

The boolean type stores one of two values: true or false.

For example, boolean isPassed = true;.

It is commonly used in conditions and decision-making statements.

Non-Primitive Data Types

Non-primitive data types are also called reference types. Unlike primitive types, they refer to objects or other reference values.

Common examples include:

Type	Example
String	String name = "Karim";
Array	int[] numbers = {1, 2, 3};
Class	Student student = new Student();
Interface	Reference to an implementing object

String is one of the most commonly used reference types in Java.

For example:

public class Main {
    public static void main(String[] args) {
        String name = "Karim";

        System.out.println(name);
    }
}

Primitive vs Non-Primitive Data Types

Primitive	Non-Primitive
Built into Java	Created from classes, interfaces, arrays, etc.
Stores basic values	Holds references to objects or other reference values
8 types	Many types
Examples: int, double, char	Examples: String, arrays, classes