Is there a concurrent version for TreeMap and TreeSet in Java Collections Framework?

By | March 5, 2023

Yes, Java provides concurrent versions of TreeMap and TreeSet in the java.util.concurrent package.

The ConcurrentSkipListMap class is a concurrent version of TreeMap that provides thread-safe access to a sorted map. Like TreeMap, it orders the elements based on their natural order or a specified comparator. However, it uses a skip list data structure instead of a binary tree, which provides better concurrency and scalability.

Similarly, the ConcurrentSkipListSet class is a concurrent version of TreeSet that provides thread-safe access to a sorted set. It is implemented using the same skip list data structure as ConcurrentSkipListMap, and offers similar performance characteristics.

Both ConcurrentSkipListMap and ConcurrentSkipListSet support the same set of operations as their non-concurrent counterparts, such as put(), get(), and remove() for maps, and add(), contains(), and remove() for sets. They also provide additional operations for navigating the map or set, such as ceilingKey(), floorKey(), higher(), and lower(), which can be useful in concurrent applications.

Note that the iterators provided by these classes are weakly consistent, meaning they may not reflect the latest updates to the map or set, but they will never throw a ConcurrentModificationException. Therefore, it is important to use appropriate synchronization mechanisms when iterating over these collections in a concurrent environment.

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