Annotation Interface Immutable

@Documented @Target(TYPE) @Retention(RUNTIME) public @interface Immutable

The class to which this annotation is applied is immutable. This means that its state cannot be seen to change by callers, which implies that

  • all public fields are final,
  • all public final reference fields refer to other immutable objects, and
  • constructors and methods do not publish references to any internal state which is potentially mutable by the implementation.

Immutable objects may still have internal mutable state for purposes of performance optimization; some state variables may be lazily computed, so long as they are computed from immutable state and that callers cannot tell the difference.

Immutable objects are inherently thread-safe; they may be passed between threads or published without synchronization.