Question

I have a Collection (a Set to be specific) and want to create a PriorityQueue from it. I also want my custom comparator, but there’s no such constructor.

PriorityQueue(Collection c)
PriorityQueue(int initialCapacity, Comparator comparator)

http://developer.android.com/reference/java/util/PriorityQueue.html

Is there any way to first create the PriorityQueue from the Collection and then add the Comparator later? If no, what’s the most efficient way to add it “manually”?

Answer 1

Basically you have two options:

1. Use the PriorityQueue(Collection c) constructor and let the elements in the collection implement the Comparable interface. (And let the priority queue fall back on the natural ordering of the elements).

2. Use the PriorityQueue(int initialCapacity, Comparator comparator) constructor, and then add all the elements of the collection, preferrably using the PriorityQueue.addAll(Collection c) method.