Skip to main content

Records in Java

What are they?

On the surface, records seem to just be syntactic sugar for producing a class that can hold some specific combination of data. They can be used to make code less verbose, but there's more to them than that. 

What do we get for free?

equals, hashCode, and toString methods are automatically implemented. If we need to deviate from the default behaviour of these methods then we can still specify the implementation in the same way that we would override those methods in a normal class.

What else is special?

Records are implicitly final, so you cannot extend from them with a sub-class. If you want to combine them with some other data then declare another Record that contains the original as a component.

That doesn't prevent us from including generics or annotations in the same way that we do with regular classes. 

Why are they?

Records are a special type of class in Java that enables developers to represent their data with less of an extensible mindset, that aligns with "Favor composition over inheritence" from Joshua Bloch's Effective Java book.

JDK Enhancement Protocol (JEP) 395 goes into more detail about the motivation and history of introducing records as a feature of the JDK.

Considerations for use

Records have been a part of Java since version 16, with Java 17 as the first long term support (LTS) version top include them.

Java 17 was release in September of 2021, so at the time of writing this post we are at a point where we can expect any stable and mature libraries to be well and truly up to speed with operating with records.

One situation where records cannot be applied is as an @Entity in the Java persistence API (JPA).

Caveat

This post has mainly been created as a refresher / reminder to myself about where records fit in Java development. I applied them in an interview about three years ago, but was a little rusty on the pros and cons when it came to a similar interview more recently.

If you want to get deeper, go and check out the JEP or other documentation. 

 

Labels:

Comments

Post a Comment

Popular posts from this blog

2022 - A year in review

Just a look back over the last 12 months. January I moved back to Christchurch to live, after having spent a few months further south since moving back from London. Work was mainly around balancing other peoples' understanding and expectations around our use of Kafka. February I decided that it would be worthwhile to have a year's subscription for streaming Sky Sports, as some rugby matches that I would want to watch would be on at time when venues wouldn't be open. Having moved to Christchurch to be close to an office, now found myself working from home as Covid restrictions came back into effect across New Zealand. March Got back into some actual coding at work - as opposed to mainly reviewing pull requests for configuration changes for Kafka topics.  This became urgent, as the command line interface tool that our provisioning system was dependent on had been marked for deprecation. April   Had my first direct experience with Covid-19.  I only went for a test because ...
Post a Comment
Read more

Speeding up Software Builds for Continuous Integration

Downloading the Internet Can you remember the last time you started out on a clean development environment and ran the build of some software using Maven or Gradle for dependency management? It takes ages to download all of the necessary third party libraries from one or more remote repositories, leading to expressions like, "Just waiting for Maven to download the Internet". Once your development environment has been used for building a few projects the range of dependencies that will need to be downloaded for other builds reduces down as the previously referenced ones will now be cached and found locally on your computer's hard drive. What happens on the Continuous Integration environment? Now consider what goes on when Jenkins or your other preferred Continuous Integration server comes to build your software. If it doesn't have a local copy of the libraries that have been referenced then it is going to pay the cost of that slow " download the Internet" p...
3 comments
Read more

Designing systems - The "ity"s That Limit or Enable Profitability

Introduction This started off as a little aide-mémoire to get my head into the right space for preparing for an interview. It's not an exhaustive list, and twists terminology that has been used to represent other things (see:  to Velocity), so don't treat it as a text book reference to work from. Most of the listed points can be associated back to so called "non-functional requirements" - NFRs. I don't like that particular terminology, so alternatively we might consider them as dimensions of the quality of the sytem. Usability "If you build it, they will come" should come with a provisor, "... but if it's awkward to use they'll soon go away, and might not come back." Security All of the aspects that combine to protect data from being seen or manipulated by anyone other than the intended recipient or sender, and also assuring users that the data has originated from the intended source. Velocity Here I'm cheating a bit by trying t...
Post a Comment
Read more