java - LinkedList 的 Collections.sort() 不起作用

Question

我正在尝试对 LinkedList 进行排序基于 Attribute优先级

飞行等级

/**
 * @author Dylan
 *
 */

/**
 * A Class to hold information for flights and allow it to be manipulated
 *
 */
public class Flight {
    private String flightID;//FlightId eg(BA001)
    Integer priority; // 1 = lowest | 9 = highest

    /**
     * A simple constructor to initialise sensible values to attributes
     */
    public Flight() {
        this.setFlightID("BA378"); //initialises the attributes to sensible values
        this.setPriority(1); //initialises the attributes to sensible values
    }
    /**
     * A param constrctor to initials attributes to values of params
     * @param flightID
     * @param priority
     */
    public Flight(String flightID, Integer priority) {
        this.flightID = flightID; // Initialises flightID to the value of the param
        this.priority = priority;// initialises priority to the value of the param
    }

    /**
     * A simple method to return the flightID
     * @return
     */
    public String getFlightID() {
        return flightID; //returns flightID
    }

    /**
     * A simple method to set the flightID
     * @param flightID
     */
    public void setFlightID(String flightID) {
        this.flightID = flightID; //sets value of flightID to params
    }

    /**
     * a simple method to return the priority of the flight
     * @return
     */
    public Integer getPriority() {
        return priority;//returns priority of the flight
    }

    /**
     * a simple method to set the priority of the flight
     * @param priority
     */
    public void setPriority(int priority) {
        this.priority = priority;//sets the flight priority to value of params
    }
    /**
     * A method to turn attributes into a sensible string
     */
    public String toString() {
        return "Flight [flightID=  " + flightID + ", priority=" + priority + "]";//toString to change attributes into a string that's easy to read
    }
}

PriorityFlightQueue1 类

import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;

public class PriorityFlightQueue1 extends AbstractFlightQueue implements Comparator<Flight> {
    LinkedList<Object> flights = new LinkedList<Object>();

    public void joinQueue(Flight f) {
        flights.addLast(f);

    }

    public Object landFlight() {
        return flights.removeFirst();
    }

    public int size() {
        return flights.size();
    }

    public void clear() {
        Iterator<Object> it = flights.iterator();//Initialise iterator to it
        while(it.hasNext()) {//A While loop to check if there's another index after the current index
            flights.removeFirst();//If the condition is true then it will remove index
        }
    }

    public void display() {
        for(Object f : flights) {//for each statement
        System.out.println(f);//prints out f to console
        }

    }

    public int compare(Flight f1, Flight f2) {
        if(f1.getPriority() < f2.getPriority()){
            return 1;
        } else {
            return -1;
        }
}
}

方法来自 FlightTestClass ，这基本上就是把数据放到链表中了。我正在尝试使用 Collections.sort() 对数据进行排序正如你在下面看到的

public void testPriorityFlightQueue1() {
        PriorityFlightQueue1    q = new PriorityFlightQueue1();

        Flight f1 = new Flight("BA001", 3);//entering flight details into the linkedlist(queue)
        Flight f2 = new Flight("NR273", 7);//entering flight details into the linkedlist(queue)
        Flight f3 = new Flight("RA291", 1);//entering flight details into the linkedlist(queue)
        Flight fref;


        showPriorityFlightQueue1(q);
        q.joinQueue(f1);
        System.out.println(f1 + " has joined the queue to land");
        showPriorityFlightQueue1(q);
        q.joinQueue(f2);
        System.out.println(f2 + " has joined the to land");
        showPriorityFlightQueue1(q);
        q.joinQueue(f3);
        System.out.println(f3 + " has joined the to land");
        showPriorityFlightQueue1(q);
        System.out.println("\n-----------------------------------------\n");    
        fref = (Flight) q.landFlight();
        System.out.println(fref + " has landed");
        showPriorityFlightQueue1(q);
        fref = (Flight) q.landFlight();
        System.out.println(fref + " has landed");
        showPriorityFlightQueue1(q);
        fref = (Flight) q.landFlight();
        System.out.println(fref + " has landed");
        showPriorityFlightQueue1(q);
        System.out.println("\n-----------------------------------------\n");

        Collections.sort(q.flights);

        showPriorityFlightQueue1(q);


    }

我真的不确定为什么它不会对 LinkedList 进行排序在 Eclipse 中，建议框显示:

The method sort(List) in the type Collections is not applicable for the arguments (LinkedList)

然后它要我转换参数 q.flights至 List<T> .

Answer 1

创建Flight比较器

public class Flight {
    private String flightID; // FlightId eg(BA001)
    Integer priority; // 1 = lowest | 9 = highest

    public static final Comparator<Flight> SORT_MAX_PRIORITY = new Comparator<Flight>() {
        @Override public int compare(Flight a, Flight b) {
            return b.priority - a.priority;
        }
    };

    public static final Comparator<Flight> SORT_MIN_PRIORITY = new Comparator<Flight>() {
        @Override public int compare(Flight a, Flight b) {
            return a.priority - b.priority;
        }
    };

    public static final Comparator<Flight> SORT_BY_ID = new Comparator<Flight>() {
        @Override public int compare(Flight a, Flight b) {
            return a.flightID.compareTo(b.flightID);
        }
    };
    // the rest of the class...
}

然后使用其中之一进行排序。

Collections.sort(q.flights, Flight.SORT_MAX_PRIORITY);