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Java Priority Queue sort using lambda expression

Priority Queue :    In Java Priority Queue is a queue which keeps its elements sorted as per their natural order( example in ascending orders for Integer, alphabetical a-z for alphabets) or using a custom Comparator at the time of creation you can custom sort it.

It has most method  similar to a queue  add, clear, poll, peek
As priority queue have to compare elements to keep in order so elements must be comparable otherwise, it will throw ClassCastException . 
As null can not be compared so you are not allowed to insert null too

A program to sort priority queue using Lambda function in Java


         class PriorityQueueLambdaJava{
    public List<Integer> KFrequent(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int j: nums) {
            map.put(j, map.getOrDefault(j, 0) + 1);
        }
        PriorityQueue<Map.Entry<Integer, Integer>> pq = new PriorityQueue<>((p1, p2) -> p1.getValue() - p2.getValue());
        map.entrySet().forEach(e -> {
            pq.offer(e);
            if (pq.size() > k) {
                pq.poll();
            }
        });
        return pq.stream().map(p -> p.getKey()).collect(Collectors.toList());
    }
}



Post is inspired form Oracle documents for java 

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