What is the closest to ConcurrentHashMap and NavigableMap in Java?

[bearophile]

Jacek Furmankiewicz:

> hashmap per thread is not an option. The cache may be a few GBs 
> of data, there is no way we can duplicate that data per thread.

But is the D garbage collector able to manage efficiently enough 
associative arrays of few gigabytes? You are not dealing with a 
GC nearly as efficient as the JavaVM one.

Bye,
bearophile