Module 5: Classes, Objects, and Constructors

Object State and the `this` Keyword

Use `this` to refer to the current object and make constructor or method code easier to read.

Author

Java Learner Editorial Team

Reviewer

Technical review by Java Learner

Last reviewed

2026-04-16

Java version

Java 25 LTS

How this lesson was prepared: AI-assisted draft, edited by hand, and checked against current Java 25 documentation and runnable examples.

Learning goals

Understand what `this` refers to
Use `this` inside constructors and methods
Disambiguate between fields and parameters with the same name

this means “this current object”: It lets a method or constructor refer to the object that is currently being worked on.

It is especially common in constructors: When a parameter and a field have the same name, this.name = name; makes the difference clear.

this also makes object-focused thinking easier: It reminds you that methods work with the state of the current object.

Beginner rule: Use this when it improves clarity, especially for field assignment.

Runnable examples

Use `this` to separate fields from parameters

class Student {
    String name;

    Student(String name) {
        this.name = name;
    }
}

public class Main {
    public static void main(String[] args) {
        Student student = new Student("Sara");
        System.out.println(student.name);
    }
}

Expected output

Sara

Common mistakes

Writing `name = name;` and expecting the field to change

Use `this.name = name;` so Java knows the field on the left and the parameter on the right.

Mini exercise

Add a constructor to a `Laptop` class that uses `this.brand = brand;` and `this.price = price;`.

Summary

`this` refers to the current object.
It is common in constructors and setters.
It helps when field names and parameter names match.

Next step

Finish the module by protecting object data with encapsulation.

Sources used

Object State and the `this` Keyword

Use `this` to separate fields from parameters

What does `this` refer to inside an object method?