Java 1.6 Features - Collection Framework Enhancements

 
   Java 1.6 provides the better bi-directional collection access on collections framework.

   The following new interfaces are added in this version:

   i) Deque - It is a double ended queue, supporting element insertion and removal at both ends. It extends the Queue interface.
   ii) BlockingDeque - Its inheriting the feature of deque and performs the operations that wait for deque to become non-empty and wait for space to become available in the deque when storing elements.
   iii) NavigableSet - It may be accessed and traversed in either ascending and descending order.
   iv) NavigableMap - It may be accessed and traversed in either ascending and descending key order.
    V) ConcurrentNavigableMap - Its similar to NavigableMap and this interface is part of java.util.concurrent.

    The following classes have been added:

     i) ArrayDeque
    ii) ConcurrentSkiplistSet
   iii) ConcurrentSkipListMap
    iv) LinkedBlockingQueue
     v) AbstractMap.SimpleEntry
    vi) AbstratMap.SimpleImmutableEntry

Other than this Two new methods were added to the Collection Utility classes:

 1. newSetFromMap(Map) -- Create a Set implementaion from Map. There is no IdentitiHashSet class but instead, just use

Set<Object> identityHashSet = Collections.newSetFromMap(new IdentityHashMap<object, Boolean>());

2. asLifoQueue(Deque) - returns a view of a Deque as a Last-in-first-out (Lifo) Queue

The Arrays utility class now has methods copyOf and copyOfRange that can efficiently resize, truncate, or copy subarrays for arrays of all types.
Before:

int[] newArray = new int[newLength];
System.arraycopy(oldArray, 0, newArray, 0, oldArray.length);
After:

int[] newArray = Arrays.copyOf(a, newLength);