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Mar 5, 2014 · If you're using an existing iterable object (say, a LinkedList) from java.util, you'll need to either subclass it and override its iterator function so that you return your own, or provide a means of wrapping a standard iterator in your special Iterator instance (which has the advantage of being more broadly used), etc.
I use a JSON library called JSONObject (I don't mind switching if I need to).. I know how to iterate over JSONArrays, but when I parse JSON data from Facebook I don't get an array, only a JSONObject, but I need to be able to access an item via its index, such as JSONObject[0] to get the first one, and I can't figure out how to do it.
The enhanced for loop is just a syntactic shortcut introduced in Java 5 to avoid the tedium of explicitly defining an iterator. For both styles, you can come up with essentially trivial variations using for , while or do while blocks, but they all boil down to the same thing (or, rather, two things).
Dec 6, 2017 · 9. Think of next as a two-step process. First it gets the next item in the iterator, then it increments the pointer to point to the next item. So, when you create a new iterator, it is initialized to return the first item (index 0) in your list. answered Dec 6, 2017 at 19:41.
Jul 1, 2014 · One way is to create a Spliterator from the Iterator and use that as a basis for your stream: Iterator<String> sourceIterator = Arrays.asList("A", "B", "C").iterator(); Stream<String> targetStream = StreamSupport.stream(. Spliterators.spliteratorUnknownSize(sourceIterator, Spliterator.ORDERED), false);
Nov 4, 2009 · Invoking this method does instantiate the Iterator object, but that is really the only overhead (not like copying all the elements). For example, looking at the type returned by the ArrayList<String>.iterator() method, we see that it is ArrayList::Itr. This is an internal class that just accesses the elements of the list directly, rather than ...
Jul 28, 2011 · An Iterable is a simple representation of a series of elements that can be iterated over. It does not have any iteration state such as a "current element". Instead, it has one method that produces an Iterator. An Iterator is the object with iteration state. It lets you check if it has more elements using hasNext() and move to the next element ...
Jul 1, 2009 · Method #1: Iterating over entries using a For-Each loop. This is the most common method and is preferable in most cases. It should be used if you need both map keys and values in the loop. Map<Integer, Integer> map = new HashMap<Integer, Integer>(); for (Map.Entry<Integer, Integer> entry : map.entrySet()) {.
May 3, 2012 · The Iterator approach would work with any type of collection, but it only supports remove operations. With the ListIterator/Iterator approach the obvious advantage is not having to copy anything since we remove as we iterate. So, this is very efficient.
Apr 14, 2013 · A third reason why iterator is a good thing on an ArrayList is that it allows you to use Java 5's for (type var : iterable) ... syntax. The bottom line is that you don't have to use iterators on ArrayList instances. If you don't want to, then don't. edited Aug 21, 2013 at 14:50. answered Apr 14, 2013 at 14:59.
