what is the use of navidableset and navigablemap why we are using that two class
Navigableset: It is used to return the closest matches of elements. For instance if it is needed to retrieve an element, which is immediately greater than, or lower than element 20 or if we want to retrieve all elements greater than or lower than 35 from sorted set elements [10,20,35,5] we can use NavigableSet. ConcurrentSkipListSet is one of the class that implements NavigableSet.
Navigablemap: Unlike the NavigableSet (return values), NaviagableMap methods is used to return the key-value pair. ConcurrentSkipListMap is the one of the class which implements NaviagableMap