Getting a NullPointerException when trying to iterate over a Queue? (Java)

Question

I'm assuming there's a logic in my error when trying to alter the queue, but I don't know what. I get a NullPointerException for the line that reads if (eventqueue.peek() != null && eventqueue.peek().leavingtime < 61200). The queue is not empty, because I can print out elements from it when I try.

The program:

QueueLinkedList<Customer> eventqueue = new QueueLinkedList<Customer>();
QueueLinkedList<Customer> customerqueue = new QueueLinkedList<Customer>();
int numberserved = 0, totalidletime = 0, longestbreak = 0, idletime = 0, linelength = 0, longestline = 0;
String[] newarr = new String[8];        

try {
    File file = new File("customersfile.txt");
    BufferedReader reader = new BufferedReader(new FileReader(file));
    reader.readLine();

    String line = null;
    while ((line = reader.readLine()) != null) {
        Customer newcust = new Customer();
        if (line.trim().length() > 0) {
            if (line.trim().charAt(0) == 'I') {
                String next;
                next = reader.readLine();
                newcust.id = Integer.parseInt(line.substring(12));
                newcust.arrtime = next.substring(14);
                newcust.setarrtimesecs(newcust.arrtime);
                newcust.setleavingtime(newcust.arrtime);    
                eventqueue.enqueue(newcust);
            }
        }
    }
} catch (IOException e) {
    e.printStackTrace();
} 

for (int clock = 32400; clock < 86400; clock++) {
    if (eventqueue.peek() != null && eventqueue.peek().leavingtime < 61200) {
        if (eventqueue.peek().arrtimesecs < 32400 || eventqueue.peek().arrtimesecs == clock) {
            if (eventqueue.peek().arrtimesecs == clock) {
                if (customerqueue.peek() == null) 
                    eventqueue.peek().waitingtime = 0;
                else 
                    eventqueue.peek().waitingtime = customerqueue.peek().leavingtime - eventqueue.peek().arrtimesecs;
            }
            if (eventqueue.peek().arrtimesecs < 32400)
                eventqueue.peek().waitingtime = 32400 - eventqueue.peek().arrtimesecs;
            customerqueue.enqueue(eventqueue.dequeue()); 
            linelength++;
            idletime = 0;
            if (longestline != 0) {
                if (linelength > longestline + 1)
                    longestline = linelength - 1;   
            }
        }

        if (customerqueue.peek().leavingtime == clock) {
            numberserved++;
            customerqueue.dequeue();
            linelength--;
            if (customerqueue.peek() == null) 
                idletime = 0;
        }

        while (customerqueue.peek() == null) {
            idletime++;
            totalidletime++;
            if (idletime > longestbreak) 
                longestbreak = idletime;
        }
    }

    else {
        if (eventqueue.peek().arrtimesecs < 61200) {
            if (eventqueue.peek().arrtimesecs == clock) {
                if (customerqueue.peek() == null) 
                    eventqueue.peek().waitingtime = 0;
                else {
                    if (customerqueue.peek().leavingtime >= 61200)
                        eventqueue.peek().waitingtime = 61200 - eventqueue.peek().arrtimesecs;
                }
                customerqueue.enqueue(eventqueue.peek()); 
                linelength++;
                idletime = 0;
                if (longestline != 0) {
                    if (linelength > longestline + 1)
                        longestline = linelength - 1;   
                }
            }

            if (customerqueue.peek().leavingtime == clock) {
                numberserved++;
                customerqueue.dequeue();
                linelength--;
                if (customerqueue.peek() == null) 
                    idletime = 0;
            }

            while (customerqueue.peek() == null) {
                idletime++;
                totalidletime++;
                if (idletime > longestbreak) 
                    longestbreak = idletime;
            }
        }

        else 
            eventqueue.peek().waitingtime = 0;
    }
}

My Queue class:

Node first, last;

public class Node {
    Customer ele;
    Node next;
}

public QueueLinkedList() {}

public boolean isEmpty() {
    return first == null;
}

public QueueLinkedList<Customer> enqueue(Customer ele) {
    Node current = last;
    last = new Node();
    last.ele = ele;
    last.next = null;

    if (current == null) 
        first = last;
    else 
        current.next = last;

    return this;
}

public Customer dequeue() {
    if (isEmpty()) 
        throw new java.util.NoSuchElementException();

    Customer ele = first.ele;
    first = first.next;     
    return ele;
}

public Customer peek() {
    Customer ele = first.ele;
    return ele;
}

public String toString(Customer cust) {
    Node curr = first;
    return "" + curr.ele;
}