Data Types in Java

⏱️ 7 min read • Beginner Level • Lesson 11

Java data types define what kind of data a variable can store. In this tutorial, you'll learn primitive and non-primitive data types, their sizes, ranges, default values, and practical examples.

Before learning data types, you should understand variables in Java since every variable must have a data type.

What are Data Types in Java?

Data types in Java define the type of data that a variable can store. They also determine the size, range, and operations that can be performed on that data.

Primitive Data Types

Java provides eight primitive data types. They are predefined by the language and represented by reserved keywords.

Example: Default Values

public class DefaultValuesTest {
    // Instance (non-static) primitives
    byte b; short sh; int a; long l;
    float f; double d; char ch; boolean bool;

    // Static field
    static int x;

    // Reference type
    String s;

    void showValues() {
        System.out.println("Default Value of byte b : " + b);
        System.out.println("Default Value of short sh : " + sh);
        System.out.println("Default Value of int a : " + a);
        System.out.println("Default Value of long l : " + l);
        System.out.println("Default Value of float f : " + f);
        System.out.println("Default Value of double d : " + d);
        System.out.println("Default Value of char ch : " + ch);
        System.out.println("Default Value of boolean bool : " + bool);
        System.out.println("Default Value of static int x : " + x);
        System.out.println("Default Value of reference String s : " + s);
    }

    public static void main(String[] args) {
        DefaultValuesTest ob = new DefaultValuesTest();
        ob.showValues();
    }
}
  

Output:

Default Value of byte b : 0
Default Value of short sh : 0
Default Value of int a : 0
Default Value of long l : 0
Default Value of float f : 0.0
Default Value of double d : 0.0
Default Value of char ch : 
Default Value of boolean bool : false
Default Value of static int x : 0
Default Value of reference String s : null

Non-Primitive Data Types

Non-primitive (reference) data types are used to store references to objects. Unlike primitive types, they do not store actual values directly in memory. Examples include String, arrays, classes, and interfaces.

These types can be used to call methods, store collections of data, and work with complex structures.

Primitive vs Non-Primitive Data Types

How Data is Stored in Memory

Primitive variables store actual values directly, whereas non-primitive variables store references to objects.

public class MemoryExample {

    public static void main(String[] args) {

        int age = 25;

        String name = "John";

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

Interview Questions ⭐

🧠 Test your understanding with a quick quiz

double a = 10/4;
System.out.println(a);

int x = 130;
byte y = (byte) x;
System.out.println(y);

🎉 Great job! Continue learning Java step by step.