27 Class declarations

A class models an entity with fields and behavior that can change.

class Counter {
  Integer value

  Void increment() {
    value = value + 1
  }
}

main() {
  Counter counter = Counter(value: 0)
  counter.increment()
  printLine(counter.value)
}

Expected output:

1

The labeled construction supplies value. Calling increment() mutates the same counter, and a later field read observes one. Methods keep state changes close to the entity they govern.

Try it: Call increment() twice and predict the result.

Precise rules: Reference.