Java Iterator overview

In Java, an iterator is an interface that can be implemented by a collection class. Any collection object can create an object of type Iterator that encapsulates references to all the objects in the original collection in some sequence, and that can be accessed using the Iterator interface methods. In other words an iterator provides an easy way to get at all the objects in a collection one at a time.

Iterator Methods list

 Iterate Example

     // For a set or list
    for (Iterator it=collection.iterator(); it.hasNext(); ) {
        Object element = it.next();
    }
   
    // For keys of a map
    for (Iterator it=map.keySet().iterator(); it.hasNext(); ) {
        Object key = it.next();
    }
   
    // For values of a map
    for (Iterator it=map.values().iterator(); it.hasNext(); ) {
        Object value = it.next();
    }
   
    // For both the keys and values of a map
    for (Iterator it=map.entrySet().iterator(); it.hasNext(); ) {
        Map.Entry entry = (Map.Entry)it.next();
        Object key = entry.getKey();
        Object value = entry.getValue();
    }

Question about Iterator

 Given:
11. ArraryList a = new ArrayList();
12. a.add(“Alpha”);
13. a.add(“Bravo”):
14. a.add(“Charlie”);
15. a.add(“Delta”);
16.Iterator iter = a.iterator();
17.

 Which two, added at line 17, print the names in the ArrayList in alphabetical order?
(Choose two)

A.  for (int i=0; i< a.size(); i++) System.out.println(a.get(i)));
B.  for (int i=0; i< a.size(); i++) System.out.println(a[i]);
C.  while( iter.hasNext() ) System.out.println(iter.next()) ;
D.  for (int i=0, i< a.size(); i++) System.out.println(iter[i]);
E.   for (int i=0; i< a.size(); i++) System.out.println(iter.get(i));