Ndtyjky

I've been given a task of making a priority queue from scratch without extension programs.

The underlying task in hand is to create a priority queue for an IT ticketing System that allows the IT workers to prioritize which tasks within the company must be completed first . (priority = 1 -> Highest priority and 4 being the lowest).

I'm attempting to do this via a singly linked list.

My issue in hand is once my insertInQueue(Ticket T) function takes the last value in it fails.

The failure return statement is

Exception in thread "main" java.lang.NullPointerException



at Queue.insertInQueue(Queue.java:36) 

(the line of code at line 36):

`if( temp.getNextTicket().getPriority() > T.getPriority())


at Main.main(Main.java:21) (The last object to go into the system)

private Ticket head;

private Ticket tail;









public void insertInQueue(Ticket T){ 



    Ticket temp = head;



    if(head == null){       //When no values are in the queue

        head = T;           //head = Ticket

        tail = T;           //tail = Ticket



    }else if(T.getNextTicket() == null){



            tail.setNextTicket(T);

            tail = T;





    }   





    else{

        while( temp != null ){



            if( temp.getNextTicket().getPriority() > T.getPriority()){



                T.setNextTicket(temp.getNextTicket());

                temp.setNextTicket(T);





            }

            temp = temp.getNextTicket();





            }

        }



    }

Example of input:

Ticket T8 = new Ticket(8, "Ben_DG", 4);

I've tried a few different things but havn't gotten anywhere. Would anybody be able to help me out?

If you need more of my code let me know and I'll post it up. (just a little concerned some class mates would steal it)

Thanks!

Since you haven't provided the rest of the code for what set and get next ticket, I can't tell for sure, but logically at some point you are trying to get a NULL value with your get method which is giving you the error. Check all your conditionals properly and see if you aren't trying to get a NULL value.

That should be the main issue and should fix it