How to Convert a Java PriorityQueue to a Max PriorityQueue

How can I modify a Java PriorityQueue to retrieve the maximum element instead of the minimum?

PriorityQueue<Integer> pq = new PriorityQueue<>();

In Java, the default behavior of the `PriorityQueue` class is to implement a min-heap. This means that the smallest element is always at the front of the queue (retrieved with `poll()`). To create a max priority queue, you can use a custom comparator that reverses the natural ordering of the elements. This way, the maximum element will be prioritized and accessible when polling from the queue.

PriorityQueue<Integer> maxPQ = new PriorityQueue<>(Collections.reverseOrder());

Causes

• The default PriorityQueue behaves as a min-heap, fetching the smallest element first.
• Java does not provide an out-of-the-box max priority queue; a custom implementation is necessary.

Solutions

• Utilize a custom comparator that inverts the natural ordering of the integers, thus forming a max-heap.
• Alternatively, use a Collections.reverseOrder() comparator to achieve the same result.

Mistake: Forgetting to define a comparator to invert the ordering.

Solution: When creating the PriorityQueue, specify a comparator like Collections.reverseOrder() to ensure it behaves as a max priority queue.

Mistake: Using a PriorityQueue without realizing it is a min heap.

Solution: Always check the behavior of your data structures; read the documentation to understand default behaviors.