FAQ: Serialization: Lesson - Serializing Associated Fields

This community-built FAQ covers the “Serializing Associated Fields” exercise from the lesson “Serialization: Lesson”.

Paths and Courses
This exercise can be found in the following Codecademy content:

[BETA] Learn Intermediate Java

FAQs on the exercise Serializing Associated Fields

There are currently no frequently asked questions associated with this exercise – that’s where you come in! You can contribute to this section by offering your own questions, answers, or clarifications on this exercise. Ask or answer a question by clicking reply (reply) below.

If you’ve had an “aha” moment about the concepts, formatting, syntax, or anything else with this exercise, consider sharing those insights! Teaching others and answering their questions is one of the best ways to learn and stay sharp.

Join the Discussion. Help a fellow learner on their journey.

Ask or answer a question about this exercise by clicking reply (reply) below!
You can also find further discussion and get answers to your questions over in Language Help.

Agree with a comment or answer? Like (like) to up-vote the contribution!

Need broader help or resources? Head to Language Help and Tips and Resources. If you are wanting feedback or inspiration for a project, check out Projects.

Looking for motivation to keep learning? Join our wider discussions in Community

Learn more about how to use this guide.

Found a bug? Report it online, or post in Bug Reporting

Have a question about your account or billing? Reach out to our customer support team!

None of the above? Find out where to ask other questions here!

Hello everyone,

I am on the Serializing Associated Fields exercise, in Java Intermediate, and I am getting the following error on line 23:
I added the Engine public class as well as the Engine method.

Car.java:23: error: constructor Engine in class Car.Engine cannot be applied to given types;
this.engine = new Engine(2.4, 6);
required: no arguments
found: double,int
reason: actual and formal argument lists differ in length
1 error

Here is the added/modified piece of code for this exercise:

public class Car implements Serializable {
private String make;
private int year;
private Engine engine;
private static final long serialVersionUID = 1L;

public class Engine implements Serializable {
private double liters;
private int cylinders;

public Car(String make, int year) {
this.make = make;
this.year = year;
this.engine = new Engine(2.4, 6);

I look forward to reading your answers. It will be greatly helpful


If you look at the additional program files, the Engine.java file is already listed with parameters and serializable. The exercise asks only for us to add “private Engine engine” as an instance variable. This worked for me, but there are other ways to achieve the same result. LMK if this makes sense.

private String make;
private int year;
private Engine engine;
private static final long serialVersionUID = 1L;
private Engine engine;

Learn Intermediate Java is such a disappointment. It’s much worse than Learn Java. What does this task want me to do, exactly? Am I supposed to add Engine as an extra class, replace the Car class with Engine class? I just added the Engine type field, as instructed, the program, as expected, returned an error (there’s no such class, Engine), but a green check sign popped up nonetheless!

Let’s add a custom reference type field to the class Car to see how the serialization process handles it.

We’ve provided a class named Engine with the following fields:

public class Engine implements Serializable{  private double liters;  private int cylinders;

Add a private Engine type field named engine to the class Car to fix the errors in the code. Observe the terminal output to see how serialization works with a custom reference type.


ya so turns out you gotta run the engine class before running the car class and it’ll work with no errors. i don’t exactly know why it gave you the green verification when the error popped up but that’s a thing for future reference i guess.