Question

I need build Queue that will stay allways sorted by its keys .
the TreeMap seams to be great for it like in this example :
http://www.javaexamples4u.com/2009/03/treemap-comparator.html
but the big problem is that its not thread safe , then i found ConcurrentNavigableMap
great , but how do i use the comparator the same way as with the TreeMap? i didn’t found any example for it .

Answer 1

It sounds like you are actually looking for a PriorityQueue. If you need a thread-safe version of it, you can use a PriorityBlockingQueue.

A priority queue is a queue where you can retrieve items ordered by “importance.” In the case of Java, you can use a Comparator or the items’ natural order (if they implement Comparable).

If you really need to use a ConcurrentNavigableMap, you will need to use an implementation of it such as ConcurrentSkipListMap. Just allocate an instance of ConcurrentSkipListMap and pass it the comparator you want to use.

new ConcurrentSkipListMap<MyKeyType, MyValueType>(new MyKeyComparator());