JAVA 鏈接列表 對為什么我不能針對鏈接列表中的節點檢查變量感到困惑？

Question

public static void check(){
        String name;
        System.out.println("Enter Customer Name to CHECK RESERVATION ticket for this Flight: ");
        Scanner input = new Scanner(System.in);
        name = input.nextLine();
        if (list.contains(name)) { //WHY IS THIS ASKING FOR SEPARATE METHOD?
            System.out.println(name +" has a Reservation on this FLight!");
            menu();
        }

我正在嘗試輸入並檢查該輸入是否在鏈接列表中。 雖然讓這個工作正常，但我遇到了問題。

如果我在我的 LinkedList.Java class 中添加新方法，它說它需要為鏈接定義一個變量。 如果有幫助，以下是我所擁有的全部內容：

import java.util.Scanner;
class airline {
public static LinkedList list = new LinkedList();

    public static void main(String[] args) {

        list.addAirplane("Allen",501);
        list.addAirplane("James",501);
        list.addAirplane("Andrea",501);
        list.addAirplane("Velvett",501);
        list.addAirplane("Paul",501);

        //Method sort the list after year the car was made
        list.sortList();
        menu();


        //Method to print all objects in List
        System.out.println(list.viewAll());

    }


    public static void menu(){
        int menuOpt;

        System.out.println("Airline Menu:");
        System.out.println("1. Reserve a Ticket");
        System.out.println("2. Cancel Reservations");
        System.out.println("3. Check Reservations");
        System.out.println("4. Display Airplanes on Flights");
        Scanner input = new Scanner(System.in);
        menuOpt=input.nextInt();
        System.out.println(menuOpt);


        switch (menuOpt){
        case 1:
            System.out.println("Reserve a Ticket");
            reserveTick();
            break;

        case 2:
            System.out.println("Cancel Reservations");
            cancel();
            break;

        case 3:
            System.out.println("Check Reservations");
            check();
            break;

        case 4:
            System.out.println("Passengers listed by Flights");
            break;

        default:
            System.out.println("INVALID RESPONSE!");
            menu();
            break;
        }
    }

    public static void reserveTick(){
        String name;
        System.out.println("Enter Customer Name to RESERVE ticket for this Flight: ");
        Scanner input = new Scanner(System.in);
        name = input.nextLine();
        list.addAirplane(name,501);
        System.out.println(name + " has been added to Flight Number 501");
        menu();
    }

    public static void cancel(){
        String name;
        System.out.println("Enter Customer Name to CANCEL ticket for this Flight: ");
        Scanner input = new Scanner(System.in);
        name = input.nextLine();

        list.remove(name, 501);
        System.out.println(name + " has been REMOVED from Flight Number 501");
        menu();
    }

    public static void check(){
        String name;
        System.out.println("Enter Customer Name to CHECK RESERVATION ticket for this Flight: ");
        Scanner input = new Scanner(System.in);
        name = input.nextLine();
        if (list.contains(name)) {
            System.out.println(name +" has a Reservation on this FLight!");
            menu();
        }
        else {
            System.out.println(name + " is not on this Flight!");
            menu();
        }
    }
    public static void listpassengers(){
        list.sortList();
    }

}

------------------------------------------------------------------



import java.util.*;
public class LinkedList
{

    private AirplaneNode head = null;

    public void addAirplane(String name , int hk)
    {    
        //If head = null then create the first node
        if(head == null)
        {
            head = new AirplaneNode(name,hk,null);
        }
        else
        {
            //If there are more than 1 node
            head = new AirplaneNode(name,hk,head);            
        }

    }


    public void sortList()
    {

        boolean sorted = false;

        while(!sorted)
        {

            sorted = true;

            for(AirplaneNode cursor = head ; cursor.getNext() != null ; cursor = cursor.getNext())
            {
                if(cursor.getHk() < cursor.getNext().getHk())
                {
                    String n = cursor.getName();
                    int hk = cursor.getHk();

                    cursor.setName(cursor.getNext().getName());
                    cursor.setHk(cursor.getNext().getHk());

                    cursor.getNext().setName(n);
                    cursor.getNext().setHk(hk);

                    sorted = false;        
                }


            }


        }



    }


    public String viewAll()
    {

        StringBuffer str = new StringBuffer();    

        for(AirplaneNode cursor = head ; cursor != null ; cursor = cursor.getNext())
        {

            str.append(cursor+"\n");
        }
        return new String(str);

    }    
}
--------------------------------------------------------------
public class AirplaneNode
{
    private String name;
    private int hk;
    private AirplaneNode next;

    public AirplaneNode(String name,int hk,AirplaneNode head)
    {
        this.name = name;
        this.hk = hk;
        this.next = head;

    }



    public AirplaneNode getNext()
    {
        return next;
    }

    public String getName()
    {
        return name;
    }

    public int getHk()
    {
        return hk;
    }

    public void setName(String in)
    {
        name = in;
    }

    public void setHk(int in)
    {
        hk = in;
    }


    public String toString()
    {
        return name + " " + hk ;
    }

}

Answer 1

好像您正在此處的頂部 package 中創建自己的 class LinkedList：

import java.util.*;
public class LinkedList
{

Since your method check() belongs in the airline class in the same package (and without any import of java.util.LinkedList) it will instead use the class you have created and that class doesn't implement any contains() method.

Answer 2

以這種方式聲明您的鏈表：

public static LinkedList<String> list = new LinkedList<String>();

編輯（根據您的評論）：

看起來您想要一個航班列表，其中每個航班都有一個乘客姓名列表。

public class Flight implements Comparable<Flight> {
    private List<String> mPassengers;
    private final int mFlight;
    private static final Collator sCollator = Collator.getInstance();
    public Flight(int flight) {
        mPassengers = new ArrayList<String>();
        mFlight = flight;
    }
    public void sortPassengers() {
        Collections.sort(mPassengers, sCollator);
    }
    public void addPassenger(String name) {
        mPassengers.add(name);
    }
    public boolean removePassenger(String name) {
        return mPassengers.remove(name);
    }
    public boolean hasPassenger(String name) {
        return mPassengers.contains(name);
    }
    public String getFlight() { return mFlight; }
    public int compareTo(Flight other) {
        return mFlight - other.mFlight;
    }
}

public static List<Flight> list = new LinkedList<Flight>();
public static void main(String[] args) {
    Flight flight = new Flight(501);
    flight.addPassenger("Allen");
    // etc. for all flight 501 passengers
    list.add(flight);

    // repeat all the above for each flight number
}

您應該可以填寫 rest。