What are Java Records?

Records have been in Java since version 16, but what are they and what can you use them for?

Records can be thought of as a replacement for simple data-holding POJOs.
These holders usually have one or more of the following properties:

• They are defined solely by the data they hold
• They have an equals() and hashCode() method based solely on their data
• Their fields are private and final, and they define a getter method for them
• They are written to and read from another format, like JSON or the database

Here is an example of such a POJO:

final class Customer {
    private final UUID id;
    private final String name;

    public Customer(UUID id, String name) {
        this.id = id;
        this.name = name;
    }

    public UUID getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    @Override
    public String toString() {
        return "Customer[id=" + id + ", name=" + name + "]";
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Customer customer = (Customer) o;
        return id.equals(customer.id) && name.equals(customer.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, name);
    }
}

Now let's see the equivalent record implementation:

record Customer(String id, String name) {}

Need we say more? You can now stop reading and start using records everywhere,
or you can continue on to Part 2: how you use Java Records.