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();
        }

I am trying to take an input and check to see if that input is in the Linked List. I am having problems though getting this to work right.

If I add the new method in my LinkedList.Java class it says it needs to define a variable for link. Below is what I have in entirety if it helps:

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

It seems as if you are creating a own class LinkedList in the top package here:

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.