How does Java's PriorityQueue differ from a min-heap?

Question

Why did they name PriorityQueue if you can\'t insertWithPriority? It seems very similar to a heap. Are there any differences? If no difference, the

Answer 1

From Java docs

Priority queue represented as a balanced binary heap: the two children of queue[n] are queue[2*n+1] and queue[2*(n+1)]. The priority queue is ordered by comparator, or by the elements' natural ordering.

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Here is a working code for maxHeap and minHeap using PriorityQueue -

class HeapDemo {
    private final static int HEAP_SIZE = 10; //size of heap

    //INNER CLASS
    static class maxHeapComparator implements Comparator {
        @Override
        public int compare (Integer x, Integer y) {
            return y-x; //reverse order
        }
    }

    public static void main(String[] args) {
        PriorityQueue minHeap = new PriorityQueue<>(HeapDemo.HEAP_SIZE); 
        PriorityQueue maxHeap = new PriorityQueue<>(HeapDemo.HEAP_SIZE, new maxHeapComparator());  

        for(int i=1; i<=HeapDemo.HEAP_SIZE; ++i){
            int data = new Random().nextInt(100) +1; //number between 0 to 100
            minHeap.add(data);
            maxHeap.add(data);
        }

        System.out.print("\nMIN Heap : ");
        Iterator iter = minHeap.iterator();
        while(iter.hasNext()){
            System.out.print(iter.next() + " ");
        }

        System.out.print("\nMAX Heap : ");
        iter = maxHeap.iterator();
        while(iter.hasNext()) {
            System.out.print(iter.next() + " ");
        }
    }
}

sample o/p :

MIN Heap : 20 32 37 41 53 91 41 98 47 86 
MAX Heap : 98 91 41 53 86 20 37 41 32 47