Re: Somewhere in this constructor of PriorityBlockingQueue is hard to understand

Holder violates the spec of https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Comparable.html.  Per the docs:
"Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false"

The bug is not in PQ it is in the 3rd party Holder implementation.

Jason

________________________________________
From: Liu <[email protected]>
Sent: Tuesday, August 4, 2020 9:07 PM
To: Jason Mehrens
Cc: Concurrency-interest
Subject: Re:Re:  [concurrency-interest] Somewhere in this constructor of PriorityBlockingQueue is hard to understand

import java.util.ArrayList;

import java.util.Queue;

import java.util.concurrent.PriorityBlockingQueue;


public class test16 {

    static class Holder implements Comparable<Holder> {

        int i;

        Holder(int i) {

            this.i = i;

        }

        public int compareTo(Holder h) {

            if(h == null)

                return  -1;

            return this.i - h.i;

        }

    }


    public static void main(String[] args) {

        ArrayList<Holder> al = new ArrayList<>(2);

        al.add(new Holder(1));

        al.add(new Holder(2));

        al.add(null);

        Queue a = new PriorityBlockingQueue<>(al);

    }

}

In this case, heapify() cound not find null item.




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