java - 不干扰原始 PriorityQueue 的 PriorityQueue 副本

Question

我正在尝试复制一个 PriorityQueue 对象。

我的目标是在不修改我原来的 PriorityQueue 的情况下更改我的 Copy 的某些对象

为了这样做，我复制了我的 PriorityQueue 并删除了我的副本的一个值，但是当我检查我的 PriorityQueue 是否仍然相同时，不幸的是原始 PriorityQueue 也被更改了......如果你有欢迎提出任何建议。

请找到我尝试过的示例:

public class PQExample
{
    public int id;
    public int price;
    public String name;
    public long date;

        public PQExample(int id, int price, String name, long time)
        {
            this.id = id;
            this.price = price;
            this.name = name;
            this.date = time;
        }

        public static void main(String[] args)
        {
            PriorityQueueComparator pqc = new PriorityQueueComparator();
            PriorityQueue<PQExample> PQ = new PriorityQueue<PQExample>(pqc);
            int setID = 1000;
            int setDate = 0;
            PQ.add(new PQExample(setID++, 24 , "Mat", setDate++));
            PQ.add(new PQExample(setID++, 25 , "Tommy", setDate++));
            PQ.add(new PQExample(setID++, 22 , "Kate", setDate++));
            PQ.add(new PQExample(setID++, 26 , "Mary", setDate++));
            PQ.add(new PQExample(setID++, 24 , "Ronny", setDate++));
            PQExample valueToDel = new PQExample(1000,22,"Mat",0);

            PriorityQueue<PQExample> PQCopy = new PriorityQueue<PQExample>();
            PQCopy = PQ;

            //Now I want to delete only in PQCopy and not in PQ    
            PQCopy.remove(valueToDel);

            //Unfortunately Mat was deleted of both objects : PQ and PQCopy...
            for (int i = 0; i < 4; i++) {
                System.out.println("Queue in: " + i + " is " + PQ.peek().name + " with the price of " + PQ.peek().price);
                PQ.poll();
            }
        }
@Override
public boolean equals(Object o)
{
    if (o instanceof PQExample)
    {
        PQExample pqExample = (PQExample)o;
        return id == pqExample.id;
    }
    return false;
}


class PriorityQueueComparator implements Comparator<PQExample>
{
    @Override
    public int compare(PQExample o1, PQExample o2) {
        if (o1.price < o2.price){return 1;}else if (o1.price > o2.price){return -1;}
        else
        {if (o1.date<o2.date){return -1;}else{return 1;}}
    }
}

Answer 1

PQcopy 只是对实际 PriorityQueue 对象的第二个引用。您想要克隆 原始PQ 而不是仅仅分配引用。 PriorityQueue has a constructor这是为你做的:

PriorityQueue<PQExample> PQCopy = new PriorityQueue<PQExample>(PQ)

顺便说一句，您应该遵循 Java 的大写约定 - 以大写字母开头的变量名是不受欢迎的。