java - 尝试解决 "The method sort(List, Comparator) in the type Collections is not applicable for the arguments"

Question

我有一项任务，必须根据紧急情况对患者进行排序，如果他们的紧急级别相同，则根据到达顺序进行排序，但是当我排序时，我收到一条错误消息:“集合类型中的方法 sort(List, Comparator) 不适用于参数(List, Comparator)”任何人都可以帮忙吗？以下是我的全部代码:

import java.util.Comparator;
public class Patient implements Comparable<Patient> {
// attributes
private String name;
private int order; // order of arrival
private int emergency; // 1 is normal, 5 is life-and-death situation

// constructor
public Patient(int order, String name, int priority) {
    this.order = order;
    this.name = name;
    this.emergency = priority;
}

// getters and setters
public int getOrder() {
    return order;
}

public void setOrder(int order) {
    this.order = order;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public int getEmergency() {
    return emergency;
}

public void setEmergency(int emergency) {
    this.emergency = emergency;
}

public String toString() {
    return name;
}

@Override
public int compareTo(Patient patient) {
    // TODO Auto-generated method stub
    int total = 0;
    if (emergency < patient.emergency) {// compares patient emergency
        total = 1;
    } else if (emergency == patient.emergency) {
        if (order < patient.order) {// compares order of arrival in case emergencies are the same
            total = -1;
        } else if (order > patient.order) {
            total = 1;
        }
    } else if (emergency > patient.emergency) {
        total = -1;
    }
    return total;
}

public static class Comparators {
    public static final Comparator<Patient> EMERGENCY = (Patient p1, Patient p2) -> Integer.compare(p1.getEmergency(), p2.getEmergency());
    public static final Comparator<Patient> ORDER = (Patient p1, Patient p2) -> Integer.compare(p1.getOrder(), p2.getOrder());

}}




import java.util.*;
public class PatientManager{
private PriorityQueue<Patient> waitingList;

public PatientManager() {
    waitingList = new PriorityQueue<Patient>();
}

// Starter method
public void start() {
    String choice;
    Scanner in = new Scanner(System.in);
    String name;
    int emergency = 0;
    int order = 0;
    List<Object> list = null;
    Patient patient;
    System.out.println("-------------------------------");
    System.out.println("(1) New Patient.");
    System.out.println("(2) Next Patient.");
    System.out.println("(3) Waiting List.");
    System.out.println("(4) Exit.");
    System.out.println("-------------------------------");

    while (true) {
        //clear screen
        System.out.print("* Choose an item from the menu: ");
        choice = in.next();
        switch (choice) {
        case "1":
            System.out.print("Enter patient's name: ");
            name = in.next();
            System.out.print("Enter emergency [1 (low) to 5 (life-and-death)]: ");

            while (emergency < 1 || emergency > 5) {//testing for emergency and if any wrong values are given clears the scanner and tries again
                try {
                    emergency = in.nextInt();
                    if (emergency < 1 || emergency > 5)
                        System.out.print("(x) Wrong value. Try again: ");
                }
                catch (Exception e) {
                    System.out.print("(x) Wrong value. Try again: ");
                    in.next();
                }
            }
            order++;//Sets the number of the arrival.
            patient = new Patient(order, name, emergency);
            waitingList.add(patient);
            System.out.println("Patient added to the waiting list.");
            emergency = 0;//resetting value of emergency otherwise all patients will have the same one and loop will not run a second time
            Arrays.sort(waitingList.toArray());
            break;
        case "2":
            if (waitingList.isEmpty()) {
                System.out.println("No more patients.");
            } else {
                patient = waitingList.remove();
                System.out.println(patient.getName() + " is treated.");
            }
            break;
        case "3":
            if (waitingList.size() == 0) {
                System.out.println("No patients in the list.");
            } else {
                System.out.println("Waiting list includes:");
                list = new ArrayList<Object>(waitingList);
                Collections.sort(list, Patient.Comparators.EMERGENCY);
                for (int i=0;i<waitingList.size();i++) {
                    System.out.println("- " + list.get(i));
                }
            }
            break;
        case "4":
            System.out.println("Program terminated. Good bye!!");
            in.close();
            System.exit(0);
            break;
        // print list name and emergency
        default:
            System.out.println("(x) Wrong choice.");
            break;
        }
    }
}}

Answer 1

问题在于您正在排序的列表已被声明为可以包含任意对象的列表。您无法将患者的比较器应用于可能不是患者的对象。

要解决这个问题，请将您的列表声明为患者列表:

List<Patient> list = new ArrayList<>(waitingList)