Thread: Help with using iterator remove on double linked list

I am trying to remove data from a double linked list using the remove method using a iterator and I keep getting a null pointer exception.

This is what I have

System.out.print("Enter student ID: ");
String studentID2 = in.next();
Iterator<Student> iter = students.iterator();
while (iter.hasNext()) {
Student stu = (Student) iter.next();
if(stu.getStudentID().equals(studentID2)){
iter.remove();
}
}

Says the error is in my remove method

public void remove() {
lastItemRet = lastItemRet.prev;
lastItemRet.next = nextItem; The error is on this line.
nextItem.prev = lastItemRet;
}

The full error I get isThe full error I get is


Exception in thread "main" java.lang.NullPointerException
at DLList$Node.access$3(DLList.java:105)
at DLList$ListIter.remove(DLList.java:182)
at Menu.display(Menu.java:46)
at Prog3.main(Prog3.java:17)