Editing Flyweight pattern (section)

=== Concurrency ===
Special consideration must be taken into account where flyweight objects are created on multiple threads. If the list of values is finite and known in advance, the flyweights can be instantiated ahead of time and retrieved from a container on multiple threads with no contention. If flyweights are instantiated on multiple threads, there are two options:

# Make flyweight instantiation single-threaded, thus introducing contention and ensuring one instance per value.
# Allow concurrent threads to create multiple flyweight instances, thus eliminating contention and allowing multiple instances per value.

To enable safe sharing between clients and threads, flyweight objects can be made into [[immutable]] [[value object]]s, where two instances are considered equal if their values are equal.