Java优先队列(PriorityQueue)重写compare操作

package myapp.kit.quickstart.utils;
 
import java.util.Comparator;
import java.util.Queue;
 
/**
 * priority queue (heap) demo.
 *
 * @author huangdingsheng
 * @version 1.0, 2020/5/8
 */
public class PriorityQueue { 
 
  public static void main(String[] args) {
 
    // min heap, process custom data struct
    Queue<Node> minHeap = new java.util.PriorityQueue<>(new Comparator<Node>(){
      @Override
      public int compare(Node o1, Node o2) {
        return o1.v - o2.v;
      }
    }); 
 
    // do sth...
    minHeap.add(new Node(1, 2));
    minHeap.add(new Node(2, 9)); 
  }
 
  // custom data struct
  static class Node {
    int k;
    int v;
    public Node(int k, int v) {
      this.k = k;
      this.v = v;
    }
  } 
}

import java.util.PriorityQueue;
public class PriorityQueueTest3 
{
 public static void main(String[] args) 
 {
 PriorityQueue pq = new PriorityQueue();
 pq.offer(6);
 pq.offer(-3);
 pq.offer(0);
 pq.offer(9);
 System.out.println(pq);
 }
}

import java.util.PriorityQueue;
public class PriorityQueueTest3 
{
 public static void main(String[] args) 
 {
 PriorityQueue pq = new PriorityQueue();
 pq.offer(6);
 pq.offer(-3);
 pq.offer(0);
 pq.offer(9);
 int len = pq.size();//这里之所以取出.size()大小，因为每一次poll()之后size大小都会变化，所以不能作为for循环的判断条件
 for(int i=0;i<len;i++){
  System.out.print(pq.poll()+" ");
 }
 System.out.println();
 }
}