Building heap in O(N) in java instead of O(NlogN) [duplicate]

Question

To build heap, we use PriorityQueue class in java. Is there a way using inbuilt library/class to build heap directly from an array in O(N) instead of pushing each element individually to build heap in O(NlogN)?

Answer 1

Use the constructor that takes a collection:

new PriorityQueue<String>(Arrays.asList(yourArray));

True to form, the Java Docs don't mention anything about complexity, but reading the source code shows that the OpenJDK uses the typical O(n) heapify approach rather than inserting in a loop:

private void initFromCollection(Collection<? extends E> c) {
    initElementsFromCollection(c);
    heapify();
}