A Functional Approach to Java

Chapter 5. Working with Records

Java 14 introduced a new type of data structure as a preview¹ feature, which was finalized two releases later: Records. They are not just another typical Java type or technique you can use. Instead, Records are a completely new language feature providing you with a simple but feature-rich data aggregator with minimal boilerplate.

Data Aggregation Types

From a general point of view, data aggregation is the process of gathering data from multiple sources and assembling it in a format that better serves the intended purpose and more preferable usage. Perhaps the most well-known kind of data aggregation type is tuples.

Tuples

Mathematically speaking, a tuple is a “finite ordered sequence of elements.” In terms of programming languages, a tuple is a data structure aggregating multiple values or objects.

There are two kinds of tuples. Structural tuples rely only on the order of the contained elements and are therefore accessible only via their indices, as seen in the following Python² code:

apple = ("apple", "green")
banana = ("banana", "yellow")
cherry = ("cherry", "red")

fruits = [apple, banana, cherry]

for fruit in fruits:
  print "The", fruit[0], "is", fruit[1]

Nominal tuples don’t use an index to access their data but use component names instead, as seen in the following Swift code:

typealias Fruit = (name: String, color: String)

let fruits: [Fruit] = [
  (name: "apple", color: "green"),
  (name: "banana", color: "yellow"),
  (name: "cherry", color: