介绍一下PriorityQueue,以及优先队列实现大小根堆

package com.algorithm.practice.heap;

import java.util.Comparator;
import java.util.PriorityQueue;

public class PriorityQueueDemo {


    public static class MinheapComparator implements Comparator<Integer> {

        @Override
        public int compare(Integer o1, Integer o2) {
            return o1 - o2; // < 0  o1 < o2  负数
        }

    }

    public static class MaxheapComparator implements Comparator<Integer> {

        @Override
        public int compare(Integer o1, Integer o2) {
            return o2 - o1; // <   o2 < o1
        }

    }

    public static void main(String[] args) {

        int[] arrForHeap = { 3, 5, 2, 7, 0, 1, 6, 4 };

        //不指定比较器,默认是从小到大排序即特殊的小根堆,(对象不指定比较器无法比较)
        PriorityQueue<Integer> minQ1 = new PriorityQueue<>();
        for (int i = 0; i < arrForHeap.length; i++) {//添加数组元素到优先队列
            minQ1.add(arrForHeap[i]);
        }
        while (!minQ1.isEmpty()) {//打印优先队列
            System.out.print(minQ1.poll() + " ");
        }
        System.out.println();

        // min heap use Comparator //指定从小到大排序实现特殊小根堆
        PriorityQueue<Integer> minQ2 = new PriorityQueue<>(new MinheapComparator());
        for (int i = 0; i < arrForHeap.length; i++) {
            minQ2.add(arrForHeap[i]);
        }
        while (!minQ2.isEmpty()) {
            System.out.print(minQ2.poll() + " ");
        }
        System.out.println();

        // max heap use Comparator//指定从大到小排序比较器实现特殊大根堆
        PriorityQueue<Integer> maxQ = new PriorityQueue<>(new MaxheapComparator());
        for (int i = 0; i < arrForHeap.length; i++) {
            maxQ.add(arrForHeap[i]);
        }
        while (!maxQ.isEmpty()) {
            System.out.print(maxQ.poll() + " ");
        }

    }

}