A specialized ConcurrentInitializer implementation which is similar to AtomicInitializer, but ensures that the initialize() method is called only once.

As AtomicInitializer this class is based on atomic variables, so it can create an object under concurrent access without synchronization. However, it implements an additional check to guarantee that the initialize() method which actually creates the object cannot be called multiple times.

Because of this additional check this implementation is slightly less efficient than AtomicInitializer, but if the object creation in the initialize() method is expensive or if multiple invocations of initialize() are problematic, it is the better alternative.

From its semantics this class has the same properties as LazyInitializer. It is a "save" implementation of the lazy initializer pattern. Comparing both classes in terms of efficiency is difficult because which one is faster depends on multiple factors. Because AtomicSafeInitializer does not use synchronization at all it probably outruns LazyInitializer, at least under low or moderate concurrent access. Developers should run their own benchmarks on the expected target platform to decide which implementation is suitable for their specific use case.