Java LanguageImmutable Objects


Immutable objects have fixed state (no setters), so all state must be known at object creation time.

Although not technically required, it is best practice to make all fields final. This will make the immutable class thread-safe (cf. Java Concurrency in Practice, 3.4.1).

The examples show several patterns that can assist with achieving this.

Related Examples

Creating an immutable version of a type using defensive copying.