Whats an iterator?
For those of you unfamiliar with the topic of iterators, here is a quick description. An iterator is an object that allows you to retrieve successive elements from a collection without requiring you to know the details of how that collection is implemented. So what does that mean? That means that an iterator will allow you to get the elements out of any collection of elements, whether that collection is an array, a linked list, a tree, whatever. It doesn’t matter. All you have to do is get the collection’s iterator and use its methods in order to begin retrieving elements from the collection. It’s up to the iterator to know how to actually get those elements from the collection. Note, however, that an Iterator is just another interface. You have no idea what object you’re actually getting returned to you when you execute the above line. All you know about it is that it implements the Iterator interface. If you look at the Iterator interface, you’ll notice that it has a handful of metho
Iterators are a common tool for traversing through all the data in order in a linked list in both the Java and C++ programming languages. In addition to defining methods for linked list manipulation, in this assignment you will define a custom iterator, ListIterator which is an inner class of SinglyLinkedList, and which implements Java’s Iterator interface. This interface has 3 methods, hasNext, next, and remove, though we really only care about hasNext and next. Anytime one wishes to go through all the elements in a linked list, one can get a custom iterator object (i.e. call the listIterator method) and as long as there are more items to fetch (hasNext is true), we can fetch the current item and move on to the next one. Note that an iterator is just a disposable object used to go through a linked list once. Each time one wishes to go through all the elements in the list, one will have to construct a brand new iterator object. So how should these methods work? Well, first of all, thin
An iterator is SQLJ’s version of a result set, but a strongly typed version–column types and (optionally) column names are specified. You declare an iterator class for each kind of iterator you want to use (where “kind of iterator” refers to iterators with a given set of columns). As with connection contexts, this strong typing is a key advantage of SQLJ. There are two categories of iterators–“named iterators”, where you specify column names as well as column types, and “positional iterators”, where you specify only column types (which SQLJ references by position instead of by name).
The iterator pattern is a common one, and in .NET it’s encapsulated in the IEnumerable and IEnumerator interfaces, and their generic counterparts. (Most of the time I’ll use the nongeneric form for descriptions and the generic form in sample code. Obviously the generic form is strongly typed where the nongeneric form isn’t, but the only other difference is that the generic form extends IDisposable.) The basic idea is that as a data consumer, you can ask an IEnumerable for an IEnumerator with the GetEnumerator() call, and then iterate over the contents of the IEnumerator (using the MoveNext() method and Current property) until either you no longer need any more data, or the iterator runs out of information to return.
The iterator pattern is a common one, and in .NET it’s encapsulated in the IEnumerable and IEnumerator interfaces, and their generic counterparts. (Most of the time I’ll use the nongeneric form for descriptions and the generic form in sample code. Obviously the generic form is strongly typed where the nongeneric form isn’t, but the only other difference is that the generic form extends IDisposable.) The basic idea is that as a data consumer, you can ask an IEnumerable for an IEnumerator with the GetEnumerator() call, and then iterate over the contents of the IEnumerator (using the MoveNext() method and Current property) until either you no longer need any more data, or the iterator runs out information to return.
