Use Cases for Java Records

  • February 11, 2024
Table Of Contents

Java Records introduce a simple syntax for creating data-centric classes, making our code more concise, expressive, and maintainable.

In this guide, we’ll explore the key concepts and practical applications of Java Records, providing a step-by-step guide to creating records and sharing best practices for using them effectively in projects. We’ll cover everything from defining components and constructors to accessing components, overriding methods, and implementing additional methods. Along the way, we’ll compare Java Records with traditional Java classes, highlighting the reduction in boilerplate code and showcasing the power and efficiency of records.

Out of clutter, find simplicity — Albert Einstein.

Java records offer a cleaner, hassle-free way to handle our data. Say goodbye to verbose classes and hello to a world where our code expresses intentions with crystal clarity. Java records are like the wizard’s tool, magically generating essential methods, leaving us with more time to focus on the business logic! 🎩✨

Example Code

This article is accompanied by a working code example
on GitHub.

Get Familiar With Java Records

In the constantly changing world of Java programming, simplicity is the most desired approach. Java records transform the way we manage data classes. It simplifies the way we implement the data classes by taking out the verbosity.

What are Java Records?

Java records are a special kind of class introduced in Java 14. They are tailored for simplicity, designed to encapsulate data without the clutter of boilerplate code. With a concise syntax, records enable us to create immutable data holders effortlessly.

Comparison to Lombok and Kotlin

Lombok: Lombok simplifies Java development by reducing boilerplate code. It offers annotations like @Data for automatic generation of methods, akin to Java records. While providing flexibility, Lombok requires external dependencies and may lack the language-level support and immutability guarantees inherent in Java records.

Kotlin: Kotlin, as a modern, concise language for the JVM, incorporates data classes that share similarities with Java records. Kotlin’s data classes automatically generate equals(), hashCode(), and toString() methods, enhancing developer productivity. Unlike Java records, Kotlin’s data classes support default parameter values and additional features within a concise syntax, providing expressive and powerful data modeling capabilities.

Why Records?

Traditionally, Java classes representing data structures contained repetitive code for methods such as equals(), hashCode(), toString(), getter/setter methods, and public constructors. This resulted in bloated classes, making the codebase more difficult to read, understand, maintain, and extend. Java records were introduced as a solution, simplifying the creation of data-centric classes and addressing the issues of verbosity and redundancy.

Let’s look at some of the benefits of using Java records.

Simplicity

One of the key advantages of records is their ability to create simple data objects without the need for writing extensive boilerplate code. With records, we can define the structure of our data concisely and straightforwardly.

Immutability by Default

Java records are immutable by default, meaning that once we create a record, we cannot modify its fields. This immutability ensures data integrity and makes it easier to reason about the state of the objects.

A Note on Immutability

Records ensure the immutability of their components by making all components provided in the constructor final. However, if a record contains a mutable object, for example an ArrayList this object itself can be modified. Furthermore, records can contain mutable static fields.

Conciseness and Readability

Java records offer a more concise and readable syntax compared to traditional Java classes. The streamlined syntax of records allows us to define our data fields and their types in a compact and visually appealing way, making it easier to understand and maintain our code.

In summary, Java records provide a powerful and efficient way to create data-centric classes. They simplify the process of defining and working with data objects, promote immutability, and enhance code readability. By leveraging the benefits of records, we can write cleaner and more maintainable code in our Java projects.

The Evolution of Java Records

  • Java 14 (March 2020): Records made their first appearance as a preview feature, giving us a glimpse into the exciting future of simplified Java programming.
  • Java 15 and 16: Records kept evolving and improving, thanks to the valuable feedback from the community.
  • Java 16 (March 2021): Records were officially established as a standard feature, indicating their readiness to shine in Java applications.

With Java records, we can experience a shift from complexity to clarity in Java programming.

In the following sections, we will dive into the details of Java records, including their syntax, use cases, and how they can bring elegance to our code.

Notes on Perview Enablement And Why We Need To Know It

  • For Java versions before 14, records are not available as a language feature.
  • For Java versions 14, 15, or between 14 and 16, we need to use the --enable-preview flag to use records.
  • For Java versions 16 and above, records are a standard feature, and the --enable-preview flag is not required for using records.

Preview features are introduced in a specific Java version but are not considered part of the official language specification until they are finalized in a subsequent release.

Here’s how we can use --enable-preview:

Compilation:

javac --enable-preview --release 14 SomeFile.java

Execution:

java --enable-preview SomeClass

In the above commands:

  • --enable-preview enables preview features during compilation and execution.
  • --release 14 specifies the Java version we are targeting. Replace 14 with the appropriate version number if we are using a different version of Java.

It is important to note that when using preview features, we might encounter changes or improvements in subsequent Java versions, and the syntax or behavior of these features could be refined before they become permanent parts of the language.

👉 Always check the official Java documentation and release notes for the specific version we are using to understand the details of the preview features and any changes made in subsequent releases.

The configurations for IDEs depend on the IDE we are using.

👉 Refer IDE documentation for specific details on code generation and other developer tools provided for implementing records.

Let’s explore the challenges we face and how Java records can help solve them. We’ll also take a closer look at the syntax of Java records to gain a better understanding.

Challenges Faced by Developers

Creating and maintaining data-centric classes in Java traditionally required substantial effort.

Traditional Java Results in Verbosity Overload

Traditional Java classes required us to write verbose code for basic functionalities like constructor, gettter, setter, equals(), hashCode(), and toString(). This verbosity cluttered the code, making it difficult to write, read and understand.

// Verbose Java class
public class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public boolean equals(Object obj) {
        // Manually written equals() method
        // ...
    }

    @Override
    public int hashCode() {
        // Manually written hashCode() method
        // ...
    }

    @Override
    public String toString() {
        // Manually written toString() method
        // ...
    }
    
    // getters and setters
}

Developers Need to Write Boilerplate Code

Writing repetitive boilerplate code was not only time-consuming but also error-prone. Any change in the class structure meant manually updating multiple methods, leading to maintenance nightmares.

Developers Need to Implement Immutability

Ensuring immutability, a key aspect of data integrity, demanded additional effort. We had to meticulously design classes to make them immutable, often leading to complex and convoluted code.

How Does Java Records Address These Issues?

Java Records, with their concise syntax, automate essential method generation, eliminating boilerplate code. They prioritize immutability by default, ensuring data integrity without manual enforcement. Automatic generation of methods like equals(), hashCode(), and toString() simplifies development, enhancing code readability and maintainability. Classes become concise, improving clarity and facilitating quick comprehension.

Syntax of Java Records

Let’s dive into the syntax of Java records, covering its key elements, various types of constructors, methods, and how records compare with traditional Java classes:

public record Person(String name, int age) {
    // Constructor and methods are automatically generated.
}

In this example, Person is a Java record with two components: name (a String) and age (an int). The record keyword signifies the creation of a record class.

A record acquires these members automatically:

  • A private final field for each of its components
  • A public read accessor method for each component with the same name and type of the component; in this example, these methods are Person::name() and Person::age()
  • A public constructor whose signature is derived from the record components list. The constructor initializes each private field from the corresponding argument.
  • Implementations of the equals() and hashCode() methods, which specify that two records are equal if they are of the same type and their corresponding record components are equal
  • An implementation of the toString() method that includes the string representation of all the record’s components, with their names

Records extend java.lang.Record, are final, and cannot be extended.

Here’s a breakdown of the essential components.

Types of Constructors

Canonical Constructor

When we declare the record, canonical constructor is automatically generated behind the scene:

public record Person(String name, int age) {
    // autogenerated code
    // private final String name;
    // private final int age;
    // public Person(String name, int age) {
    //     this.name = name;
    //     this.age = age;
    // }
}

public Person(String name, int age) is the canonical constructor (all-arguments constructor) generated for us.

Compact Constructor

A compact constructor enables developers to add custom logic during object initialization. This constructor is explicitly declared within the record and can perform additional operations beyond the simple initialization.

However, unlike a class constructor, a record constructor doesn’t have a formal parameter list; this is called a compact constructor.

By providing an opportunity to perform custom operations during initialization, developers can ensure that their objects are correctly and completely initialized before they are used. For example, we can implement data validation rules before initializing the fields:

public record Person(String name, int age) {
    // consturctor defined by the developer
    // Remember that it not like a standard constructor
    // We do not declare the constructor arguments
    // Just add body with custom logic
    public Person {
        // do not accept bad input
        if (age < 0) {
            throw new IllegalArgumentException("Age must be greater than zero.");
        }
    }
}

// Usage
Person person = new Person("Alice", 30); // Valid
Person invalidPerson = new Person("Bob", -5); // Throws IllegalArgumentException

For example, the record Person has fields name and age. Its custom constructor checks if the age is negative. If yes, it throws a IllegalArgumentException.

Default Constructor

Records can have a default constructor that initializes all components to their default values. This must delegate, directly or indirectly, to the canonical constructor:

public record Person(String name, int age) {
    public Person() {
        // we must call the canonical constructor
        this("Foo", 50);
    }

}

// Usage
Person person = new Person(); // Components initialized to "Foo" and 50

In this example, it will generate the no-arguments constructor (Java’s standard default initialization for the object state):

// autogenerated cannonical constructor
public Person(String name, int age) {
    this.name = name;
    this.age = age;
}

public Person() {
    this("Foo", 50);
}

Custom Constructor

We can create custom constructors with subset of parameters, allowing flexibility in object creation. This must delegate, directly or indirectly, to the canonical constructor:

public record Person(String name, int age) {
    public Person {
        if (name == null) {
            throw new IllegalArgumentException("Name cannot be null.");
        }
    }

    public Person(int age) {
        this("Bob", age);
    }
}

// Usage
Person person = new Person("Alice", 30); // Valid
Person unknownPerson 
    = new Person(25); // Uses custom constructor with default name "Bob"

In this example, we can create a custom constructor that only takes in the age parameter. This means that when we create an instance of the Person class, we only need to provide the age value. The other properties will be set to their default values.

This feature is especially useful when dealing with large and complex classes that have many properties. It allows developers to create objects quickly and efficiently without having to specify all the properties every time.

How to Access Components?

Components in a record are implicitly final, making them immutable. Records automatically generate getters for components, providing read-only access:

Person person = new Person("Alice", 30);
String name = person.name(); // Getter for 'name'
int age = person.age(); // Getter for 'age'

When working with records in Java, it is important to understand how to access their components. Components are the individual fields or properties that make up a record. For example, in the code above, the Person record has two components: name and age.

To access the components of a record, we first need to create an instance of the record using the new keyword. In this case, we are creating a new Person record and assigning it to a variable called person. The values Alice and 30 are passed as arguments to the Person constructor, which initializes the name and age components of the record.

Once we have an instance of the record, we can access its components using getters. Getters are methods that are automatically generated by the Java compiler for each component of a record. In the code above, we are using the name() and age() getters to retrieve the values of the name and age components, respectively. As these are read only properties, there are no setters available for name and age.

How to Override Methods?

Records automatically generate methods like equals(), hashCode(), and toString() based on components. We can customize these methods if needed:

public record Person(String name, int age) {
    // Automatically generated methods can be overridden
    @Override
    public String toString() {
        return String.format("Person{name='%s', age=%d}", name, age);
    }
}

// Usage
Person person = new Person("Alice", 30);
System.out.println(person); // Output: Person{name='Alice', age=30}

How to Delegate Methods?

Record methods can delegate behavior to other methods within the record or external methods. This enables code reuse and modular design:

public record Person(String name, int age) {
    public Person withName(String name) {
        return new Person(name, age);
    }
}

// Usage
Person person = new Person("Alice", 50); // Person[name=Alice, age=50]
Person newPerson = person.withName("Tom"); // Person[name=Tom, age=50]

How to Implement Methods?

We can add additional methods to records, allowing them to encapsulate behavior related to the data:

public record Person(String name, int age) {
    public boolean isAdult() {
        return age >= 18;
    }
}

// Usage
Person person = new Person("Alice", 30);
System.out.println(person.isAdult()); // Output: true

One-to-one Comparison

Let’s compare a record with a traditional Java class to highlight the reduction in boilerplate code:

// Traditional Java class
public class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    @Override
    public boolean equals(Object obj) {
        // Manually written equals() method
        // ...
    }

    @Override
    public int hashCode() {
        // Manually written hashCode() method
        // ...
    }

    @Override
    public String toString() {
        // Manually written toString() method
        // ...
    }
}

The equivalent Java record achieves the same functionality with significantly less code:

// Java record
public record Person(String name, int age) {}

Java records not only enhance readability and maintainability but also promote a more expressive and concise coding style, allowing us to focus on the core logic of their applications.

Maintain the Overall Immutability of the Record

If a record contains non-primitive or mutable components, ensure that these components are also immutable or use defensive copies to maintain the overall immutability of the record:

public record Address(String city, List<String> streets) {
    // Automatically generated methods ensure immutability, but caution with mutable components
}

List<String> streets = new ArrayList<>();
streets.add("Street 1");
streets.add("Street 2");

Address address = new Address("City", List.copyOf(streets));
streets.add("Street 3");

System.out.println(address.streets()); // Output: [Street 1, Street 2]

What Are the Best Practices for Using Records?

Let’s explore best practices for using Java records effectively in projects, guidelines for maintaining code consistency and readability, and practical applications and conclusions.

Choose Appropriate Use Cases

Choosing the appropriate use cases for Java records is paramount. Utilize records for simple data carriers where immutability and value semantics are crucial. However, refrain from employing records for classes with complex business logic or abundant behavior:

  • Use Case 1: Configuration Settings: Use records to represent configuration settings for an application. These settings are typically immutable, and their value semantics are crucial for consistent behavior across the application’s lifecycle.
  • Use Case 2: DTOs in RESTful Services: Apply records for Data Transfer Objects (DTOs) in RESTful services. DTOs often serve as simple data carriers between the client and server, emphasizing immutability to prevent unintended modifications during data transmission.

Avoid Overcomplication

Avoid overcomplicating records. Resist the temptation to overload them with unnecessary methods. Embrace simplicity, letting records manage fundamental operations like equals(), hashCode(), and toString():

  • Use Case 1: Domain Entities: Employ records to model simple domain entities where basic CRUD operations suffice. Avoid cluttering these entities with unnecessary methods, letting records automatically handle essential operations for improved code maintainability.
  • Use Case 2: Event Payloads: Use records to represent event payloads in an event-driven architecture. Overcomplicating these payloads with excessive methods is unnecessary; records naturally handle equality and string representation, simplifying event handling.

Ensure Immutability

Ensuring immutability is key to leveraging the benefits of Java records. Keep components final to enforce immutability. In cases where a component is mutable, such as a collection, create defensive copies during construction to maintain the desired immutability:

  • Use Case 1: Currency Conversion Rates: Represent currency conversion rates using records. As these rates are immutable once defined, marking the components as final ensures that the rates remain constant throughout the application’s execution.
  • Use Case 2: Configuration Properties: Utilize records for storing configuration properties, such as database connection details. Immutability is crucial to prevent unintended modifications to these properties, ensuring the stability of the application’s configuration.

Avoid Business Logic in Records

Steer clear of embedding business logic within records. Maintain the focus of records on data representation and delegate business logic to separate classes. This approach enhances maintainability and adheres to the principle of separation of concerns:

  • Use Case 1: Employee Information: Model employee information using records but avoid incorporating complex business logic. Instead, delegate tasks like salary calculations or performance assessments to separate classes, adhering to the best practice of separation of concerns.
  • Use Case 2: Sensor Readings: Use records to represent sensor readings in an Internet of Things (IoT) application. Keep records focused on data representation, and delegate any complex processing or analysis of sensor data to dedicated classes.

Maintain Readability

To maintain readability, adhere to consistent naming conventions for both record classes and their components. Meaningful names for records and components contribute to code clarity, making it easier for developers to understand the structure and purpose of the classes:

  • Use Case 1: User Preferences: Apply records to store user preferences in a system. Consistent naming conventions for record classes and components enhance code readability, making it easier for developers to understand and modify user preference-related code.
  • Use Case 2: Geographic Coordinates: Represent geographic coordinates using records. Meaningful names for record classes and components contribute to the clarity of the code, allowing developers to quickly comprehend the structure and purpose of the geographic coordinate representation.

Ways to Master Java Records

Let’s Recap the Key Concepts

We learnt that Java records streamline data class creation, reducing redundant code. They prioritize immutability and value semantics, ensuring that instances of records represent fixed data values. With records, developers can focus on defining the structure and properties of their data without being burdened by repetitive code.

Then we understood the automatic method generation offered by Java records. Java records automatically generate essential methods such as equals(), hashCode(), and toString(). This automation guarantees consistent behavior across different record instances, enhancing code reliability and reducing the likelihood of errors. By providing these methods out of the box, records simplify the development process and enable developers to work more efficiently.

Finally, we covered the best practices for effective use of Java records. Adhering to best practices is essential for leveraging the benefits of Java records effectively. This includes selecting appropriate use cases where immutability and value semantics are crucial, such as simple data carriers. Additionally, maintaining readability through consistent naming conventions and avoiding overcomplication ensures that records remain manageable and easy to understand throughout the development lifecycle. Following these practices fosters a more robust and maintainable codebase.

Next Steps We Should Take

Here are few steps you can take in order to master the Java record concepts:

  • Apply the Concepts Learned: Do not just stop at understanding — implement records in projects. Create immutable, clean, and readable data classes.
  • Experiment and Refine: Play with different scenarios and refine understanding. Experimentation leads to mastery.
  • Share and Collaborate: Share knowledge with peers, and collaborate on projects to learn from real-world use cases.
  • Refer Official Java Documentation: Dive deep into the official documentation to explore advanced topics and nuances.
  • Read JDK Enhancement Proposal for Java Records: Refer official documentation to know more about the proposal for enhancements to the JDK for Java records.

Conclusion

In this article, we learnt how Java records make data class construction easier by reducing repetitive code and automating functions such as equals(), hashCode(), and toString(). Following best practices promotes effective use, focusing on appropriate scenarios and preserving code readability. Adopting records results in more efficient and manageable Java codebases.

Equipped with the knowledge of Java records, go, create, innovate, and let the code shape the future!

Happy coding! 🚀

Written By:

Sachin Raverkar

Written By:

Sachin Raverkar

Sachin is a Java enthusiast with over two decades of product development expertise. He enjoys architecting and delivering SAAS products as well as sharing expertise with people all over the world.

Recent Posts

Creating and Publishing an NPM Package with Automated Versioning and Deployment

In this step-by-step guide, we’ll create, publish, and manage an NPM package using TypeScript for better code readability and scalability. We’ll write test cases with Jest and automate our NPM package versioning and publishing process using Changesets and GitHub Actions.

Read more

Offloading File Transfers with Amazon S3 Presigned URLs in Spring Boot

When building web applications that involve file uploads or downloads, a common approach is to have the files pass through an application server.

Read more

One Stop Guide to Java Functional Interfaces

Introduction to Functional Programming Functional programming is a paradigm that focuses on the use of functions to create clear and concise code.

Read more