Data Oriented Programming in Java

Key Takeaways

  • Project Amber has brought a number of new features to Java in recent years. While each of these features are self-contained, they are also designed to work together. Specifically, records, sealed classes, and pattern matching work together to enable easier data-oriented programming in Java.
  • OOP encourages us to model complex entities and processes using objects, which combine state and behavior. OOP is at its best when it is defining and defending boundaries. 
  • Java’s strong static typing and class-based modeling can still be tremendously useful for smaller programs, just in different ways.
  • Data-oriented programming encourages us to model data as (immutable) data, and keep the code that embodies the business logic of how we act on that data separately. Records, sealed classes, and pattern matching, make that easier.
  • When we’re modeling complex entities, OO techniques have a lot to offer us. But when we’re modeling simple services that process plain, ad-hoc data, the techniques of data-oriented programming may offer us a straighter path.
  • The techniques of OOP and data-oriented programming are not at odds; they are different tools for different granularities and situations. We can freely mix and match them as we see fit.

Project Amber has brought a number of new features to Java in recent years — local variable type inferencetext blocksrecords, sealed classes, pattern matching, and more. While each of these features are self-contained, they are also designed to work together. Specifically, records, sealed classes, and pattern matching work together to enable easier data-oriented programming in Java. In this article, we’ll cover what is meant by this term and how it might affect how we program in Java.

Object-oriented programming

The goal of any programming paradigm is to manage complexity. But complexity comes in many forms, and not all paradigms handle all forms of complexity equally well. Most programming paradigms have a one-sentence slogan of the form “Everything is a …”; for OOP, this is obviously “everything is an object.” Functional programming says “everything is a function”; actor-based systems say “everything is an actor”, etc. (Of course, these are all overstatements for effect.)

OOP encourages us to model complex entities and processes using objects, which combine state and behavior. OOP encourages encapsulation (object behavior mediates access to object state) and polymorphism (multiple kinds of entities can be interacted with using a common interface or vocabulary), though the mechanisms for accomplishing these goals vary across OO languages. When modeling the world with objects, we are encouraged to think in terms of is-a (a savings account is-a bank account) and has-a (a savings account has-a owner and account number) relationships.

While some developers take pleasure in loudly declaring object-oriented programming to be a failed experiment, the truth is more subtle; like all tools, it is well-suited to some things and less well-suited to others. OOP done badly can be awful, and a lot of people have been exposed to OOP principles

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