Java PriorityQueue比较器-如何/何时排序？ [英] Java PriorityQueue Comparator - How/When do you sort?

问题描述

我正在初始化一个优先级队列，例如：

I'm initialising a Priority Queue like:

strategy = new FuelPriority();
incoming = new PriorityQueue<Vehicle>(1, strategy);

我的Comparator类的代码为：

The code for my Comparator class is:

public class FuelPriority implements Comparator<Object> {

public int compare(Object o1, Object o2) {

    Vehicle a1 = (Vehicle) o1;
    Vehicle a2 = (Vheicle) o2;

    return Integer.compare(a1.getFuelLevel(), a2.getFuelLevel());
  }
}

运行模拟后，元素未排序完全是随机的；我在 FuelPriority 类的compare方法中设置了一个断点，但根本没有调用它。
我在这里缺少什么吗？

After running a simulation, the elements aren't ordered at all - they are random; I set a breakpoint in the compare method of my FuelPriority class, but it wasn't called at all. Am I missing something here?

推荐答案

除了您的代码中的错字，它对我也有用。

Aside from the typo on your code, it works for me.

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

public class StackOverflow
{
    public static void main(String[] args)
    {

        FuelPriority strategy = new FuelPriority();
        PriorityQueue<Vehicle> incoming = new PriorityQueue<Vehicle>(4, strategy);
        incoming.add(new Vehicle("car1", 10));
        incoming.add(new Vehicle("car2", 20));
        incoming.add(new Vehicle("car3", 15));
        incoming.add(new Vehicle("car4", 1));

        // to retrieve the elements in order
        while (!incoming.isEmpty()) {
            System.out.println(incoming.poll());
        }

    }

}

class FuelPriority
    implements Comparator<Object>
{

    public int compare(Object o1, Object o2)
    {

        Vehicle a1 = (Vehicle)o1;
        Vehicle a2 = (Vehicle)o2;

        return Integer.compare(a1.getFuelLevel(), a2.getFuelLevel());
    }
}

class Vehicle
{

    private String name;
    private int fuelLevel;

    public Vehicle(String name, int fuelLevel)
    {
        this.name = name;
        this.fuelLevel = fuelLevel;
    }
    public int getFuelLevel()
    {
        return fuelLevel;
    }

    @Override
    public String toString()
    {
        return name + "=" + fuelLevel;
    }
}

这篇关于Java PriorityQueue比较器-如何/何时排序？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！