Java Data Types

In Java, every value has a type. A data type tells the program what kind of data a variable can hold — such as a number, a character, or a true/false value. Java is a strongly typed language, meaning the data type of every variable must be declared before it is used.

Data types in Java are divided into two main categories: Primitive Data Types and Non-Primitive (Reference) Data Types.

1. Primitive Data Types

Primitive data types are the most basic building blocks of data in Java. There are 8 primitive data types in Java. Each one stores a specific kind of value and occupies a fixed amount of memory.

Overview Table

byte

The byte data type stores very small whole numbers. Its range is from -128 to 127. It is useful when saving memory is important, such as in large arrays.

public class DataTypeDemo {
    public static void main(String[] args) {
        byte age = 25;
        System.out.println("Age: " + age);
    }
}

short

The short data type stores small whole numbers. Its range is from -32,768 to 32,767. It is rarely used in modern Java.

short temperature = -200;
System.out.println("Temperature: " + temperature);

int

The int data type is the most commonly used type for whole numbers. Its range is from -2,147,483,648 to 2,147,483,647. Unless there is a specific reason to use another integer type, int is the default choice.

int salary = 50000;
System.out.println("Salary: " + salary);

long

The long data type is used when numbers exceed the range of int. Long values must be followed by the letter L to distinguish them from int.

long worldPopulation = 8000000000L;
System.out.println("World Population: " + worldPopulation);

float

The float data type stores decimal numbers with up to 7 significant digits. Float values must be followed by the letter f.

float price = 19.99f;
System.out.println("Price: " + price);

double

The double data type is the default for decimal numbers and is more precise than float — it supports up to 15 significant digits. It does not need a suffix.

double piValue = 3.14159265358979;
System.out.println("Pi: " + piValue);

char

The char data type stores a single character. The value must be enclosed in single quotes.

char grade = 'A';
System.out.println("Grade: " + grade);

Java stores characters as Unicode values. So 'A' is actually stored as the number 65 internally.

boolean

The boolean data type holds only two possible values: true or false. It is commonly used in conditions and decision-making.

boolean isLoggedIn = true;
boolean hasPaid = false;
System.out.println("Logged in: " + isLoggedIn);
System.out.println("Has paid: " + hasPaid);

2. Non-Primitive (Reference) Data Types

Non-primitive data types are not predefined by Java — they are created by the programmer. They refer to objects stored in memory, which is why they are also called reference types.

Common non-primitive data types include:

• String: A sequence of characters. Example: "Hello, Java!"
• Arrays: A collection of values of the same type.
• Classes: User-defined blueprints for creating objects.
• Interfaces: Abstract contracts for classes to implement.

String name = "Alice";
System.out.println("Name: " + name);

Unlike primitive types, non-primitive types can be null — meaning they point to no object at all.

Difference Between Primitive and Non-Primitive

Complete Example

public class AllDataTypes {
    public static void main(String[] args) {
        byte b = 10;
        short s = 500;
        int i = 75000;
        long l = 9000000000L;
        float f = 5.75f;
        double d = 19.99999;
        char c = 'J';
        boolean flag = true;
        String text = "Java is fun";

        System.out.println("byte: " + b);
        System.out.println("short: " + s);
        System.out.println("int: " + i);
        System.out.println("long: " + l);
        System.out.println("float: " + f);
        System.out.println("double: " + d);
        System.out.println("char: " + c);
        System.out.println("boolean: " + flag);
        System.out.println("String: " + text);
    }
}

Output:

byte: 10
short: 500
int: 75000
long: 9000000000
float: 5.75
double: 19.99999
char: J
boolean: true
String: Java is fun

Summary

• Java has 8 primitive data types: byte, short, int, long, float, double, char, and boolean.
• Use int for whole numbers and double for decimal numbers in most cases.
• Use char for a single character and boolean for true/false values.
• Non-primitive types include String, arrays, and classes — they store references to objects.
• Java is strongly typed: every variable must have a declared type before use.