ImmutablePerson

ImmutablePerson is a data object designed to represent a person with fixed attributes that cannot be altered after creation. The emphasis on immutability makes instances thread-safe and easy to reason about, since their state remains constant once constructed.

Typical attributes include firstName, lastName, dateOfBirth, and an optional middleName or middleInitial, along with an identifier such as id. Implementations ensure that all fields are immutable or exposed as read-only. If a field references a mutable component, such as a date or address object, the implementation should defensively copy or store it in an immutable form to preserve invariants.

Construction and modification follow immutability principles. Instances are created via constructors or factory methods. To represent a change, you create a new ImmutablePerson, often using withX-style methods (for example, withLastName) or a builder pattern. This approach preserves immutability while allowing variations without altering existing instances.

Equality and hashing are typically value-based. Two ImmutablePerson objects are considered equal when their significant fields match, and their hash codes are derived from those fields. This supports effective use as keys in maps or elements in sets and ensures predictable behavior across collections.

Use cases for ImmutablePerson include data transfer objects, historical records, caching keys, and concurrency-friendly data models. They enable safe sharing across threads and simplify reasoning in functional programming styles, at the expense of potentially increased allocations when creating modified variants.

Common design considerations involve deciding which fields to include, how to represent optional data, and how to manage nested or composite immutable components. Language-specific patterns include Java final fields, Kotlin data classes, Python frozen dataclasses, or Rust structs with immutable fields.