Java’s evolution in data-oriented programming is taking a significant step forward with the introduction of carrier classes and interfaces, building upon the foundation laid by records. These features are part of Project Amber’s initiative to improve Java’s data handling capabilities by extending the benefits of records into more flexible data structures.
Carrier classes offer a new way to define data holders with a more dynamic representation while still benefitting from the reduced boilerplate, pattern matching destructuring, and reconstruction support that records provide. They achieve this by allowing developers to declare a state description and manage their own implementations. This enables the use of component fields and compact constructors to automatically generate accessor methods, Object methods, and deconstruction patterns.
Unlike records, carrier classes support inheritance (as they are non-final) and mutability (through non-final fields), making them a versatile tool for developers. They also pave the way for abstract records and introduce carrier interfaces, which facilitate pattern matching and offer a more relaxed deconstruction pattern. This flexibility is particularly valuable for evolving types and adding new components without breaking existing code.
Through carrier classes and interfaces, Java promises not only enhanced data-oriented capabilities but also a more streamlined and adaptable framework for managing complex data structures efficiently.

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Java is introducing carrier classes and interfaces as part of Project Amber to enhance data-oriented programming beyond records. Carrier classes allow developers to define flexible data holders with reduced boilerplate while supporting inheritance and mutability, unlike records which are final and immutable. They automatically generate accessor methods, Object methods, and deconstruction patterns from declared state descriptions. Carrier interfaces enable pattern matching with relaxed deconstruction patterns, making it easier to evolve types and add components without breaking existing code.

Exploring Carrier Classes and Interfaces in Java's Data-Oriented Programming