What is the simplest way to make a class immutable in Java?

Use records if possible. They are inherently immutable.

How can you make a class immutable if records can't be used?

Make all fields final and the class itself final. Also, create defensive copies for mutable objects.

Why should a class be made final to be immutable?

To prevent subclassing which might introduce mutable state.

What should you consider when handling mutable objects in constructors?

Make defensive copies of mutable objects like lists or maps.

How can accessors contribute to class immutability?

Ensure they do not expose references to internal mutable state.

Which JDK classes are inherently non-modifiable?

Classes like String, Integer, Long, and other wrapper classes.

What is defensive copying?

Creating a new copy of an object to prevent external modifications.

How to make a class immutable? - Cracking the Java Coding Interview

00:01:00

https://www.youtube.com/watch?v=GBWFd77J9EE

Resumen

TLDRThis guidance explains how to create immutable classes with a focus on using records when possible, as they simplify the process by being inherently immutable. If records cannot be used, it is essential to make all class fields and the class itself final, to avoid inheritance that might allow mutable state. It's also crucial to handle mutable objects, like lists and maps, by making defensive copies in constructors and accessors to prevent modifications. Final classes and defensive copying are key strategies in maintaining immutability. Moreover, JDK's String, Integer, and wrapper classes serve as examples of non-modifiable types.

Para llevar

📝 Prefer using records to create immutable classes.
🛡️ Make all fields and the class final if not using records.
🔄 Use defensive copies for mutable objects in constructors.
🚫 Avoid exposing references through accessors.
🔍 Study JDK classes like String for non-modifiable examples.
👩‍💻 Ensure immutability to prevent unintended state changes.
🤖 Utilize polymorphism cautiously with mutable states.

Cronología

00:00:00 - 00:01:00
To make a class immutable, prefer using records if applicable. If not, ensure all fields are final, and make the class itself final to prevent extension. Defensively copy mutable objects passed to constructors or returned by accessors to avoid state modifications through vulnerabilities. Note that primitive wrapper classes like String and Integer in the JDK are inherently immutable, serving as practical examples.

Mapa mental

Vídeo de preguntas y respuestas

What is the simplest way to make a class immutable in Java?
Use records if possible. They are inherently immutable.
How can you make a class immutable if records can't be used?
Make all fields final and the class itself final. Also, create defensive copies for mutable objects.
Why should a class be made final to be immutable?
To prevent subclassing which might introduce mutable state.
What should you consider when handling mutable objects in constructors?
Make defensive copies of mutable objects like lists or maps.
How can accessors contribute to class immutability?
Ensure they do not expose references to internal mutable state.
Which JDK classes are inherently non-modifiable?
Classes like String, Integer, Long, and other wrapper classes.
What is defensive copying?
Creating a new copy of an object to prevent external modifications.