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<title>Status File for Jakarta Commons "Collections" Package</title>
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<h1>The Jakarta Commons <em>Collections</em> Package</h1>
$Id: STATUS.html,v 1.22 2002/12/13 12:04:16 scolebourne Exp $<br>
<a href="#Introduction">[Introduction]</a>
<a href="#Dependencies">[Dependencies]</a>
<a href="#Release Info">[Release Info]</a>
<a href="#Committers">[Committers]</a>
<a href="#Action Items">[Action Items]</a>
<br><br>
</div>
<a name="Introduction"></a>
<h3>1. INTRODUCTION</h3>
<p>The <em>Collections</em> package contains a set of Java classes that
extend or augment the Java Collections Framework.
The following classes are included:</p>
<ul>
<li><strong>ArrayStack</strong> - An implementation of the java.util.Stack API
that is based on an ArrayList instead of a Vector, so it is not synchronized to
protect against multi-threaded access.</li>
<li><strong>Bag</strong> - A Collection that keeps a count of its members of the same
type, using <code>hashCode</code> to check for equality. Suppose
you have a Bag that contains <code>{a, a, b, c}</code>. Calling
getCount on <code>a</code> would return 2, while calling
uniqueSet would return <code>{a, b, c}</code>. <i>Note: this is an
interface with several implementations.</i></li>
<li><strong>BagUtils</strong> - Provides utility methods and decorators
for Bag and SortedBag instances.</li>
<li><strong>BeanMap</strong> - An implementation of the java.util.Map API
that is based on a JavaBean using introspection. The property names are the
keys of the map and the property values are the values of the map.</li>
<li><strong>BinaryHeap</strong> - Binary heap implementation
of PriorityQueue and Buffer.</li>
<li><strong>BoundedCollection</strong> - an interface used by collections that can
have a variable number of elements up to a fixed bound.</li>
<li><strong>BoundedFifoBuffer</strong> - a very efficient implementation of
Buffer that does not alter the size of the buffer at runtime.</li>
<li><strong>Buffer</strong> - a collection that allows objects to be removed
in some well-defined order.</li>
<li><strong>BufferUtils</strong> - Contains static utility methods for
buffers.</li>
<li><strong>CollectionUtils</strong> - a variety of helper methods
for working with collections.</li>
<li><strong>ComparatorUtils</strong> - Contains static utility methods for
comparators.</li>
<li><strong>CursorableLinkedList</strong> - an implementation of the java.util.List
interface supporting a java.util.ListIterator that allows concurrent
modifications to the underlying list.</li>
<li><strong>DoubleOrderedMap</strong> - Red-Black tree-based implementation of Map.
This class guarantees
that the map will be in both ascending key order and ascending
value order, sorted according to the natural order for the key's
and value's classes.</li>
<li><strong>ExtendedProperties</strong> - extends normal Java properties by adding
the possibility to use the same key many times, concatenating the value strings
instead of overwriting them.</li>
<li><strong>FastArrayList</strong> - a custom implementation of java.util.ArrayList
designed to operate in a multithreaded environment where the large majority of
method calls are read-only, instead of structural changes.</li>
<li><strong>FastHashMap</strong> - a custom implementation of java.util.HashMap
designed to operate in a multithreaded environment where the large majority of
method calls are read-only, instead of structural changes.</li>
<li><strong>FastTreeMap</strong> - a custom implementation of java.util.TreeMap
designed to operate in a multithreaded environment where the large majority of
method calls are read-only, instead of structural changes.</li>
<li><strong>HashBag</strong> - An implementation of <strong>Bag</strong> that is backed by a
HashMap.</li>
<li><strong>IteratorUtils</strong> - Contains static utility methods for
iterators.</li>
<li><strong>ListUtils</strong> - miscelaneous utilities to manipulate Lists.</li>
<li><strong>MultiMap</strong> - This is simply a Map with slightly different semantics.
Instead of returning an Object, it returns a Collection.
So for example, you can put( key, new Integer(1) );
and then a Object get( key ); will return you a Collection
instead of an Integer. This is an interface implemented
by <strong>MultiHashMap</strong>.</li>
<li><strong>PriorityQueue</strong> - a PriorityQueue interface, with
<strong>BinaryHeap</strong> and <strong>SynchronizedPriorityQueue</strong>
implementations.</li>
<li><strong>ProxyMap</strong> - This <code>Map</code> wraps another <code>Map</code>
implementation, using the wrapped instance for its default
implementation. This class is used as a framework on which to
build to extensions for its wrapped <code>Map</code> object which
would be unavailable or inconvenient via sub-classing (but usable
via composition).</li>
<li><strong>ReferenceMap</strong> - Hashtable-based Map implementation that
allows mappings to be removed by the garbage collector.</li>
<li><strong>SequencedHashMap</strong> - A map of objects whose mapping entries are
sequenced based on the order in
which they were added.</li>
<li><strong>SortedBag</strong> - A type of <strong>Bag</strong> that maintains order among its unique
representative members</li>
<li><strong>StaticBucketMap</strong> - An efficient, thread-safe
implementation of java.util.Map that performs well in in a highly
thread-contentious environment.</li>
<li><strong>StringStack</strong> - A stack for string objects.</li>
<li><strong>SynchronizedPriorityQueue</strong> - A thread-safe version of
the priority queue.</li>
<li><strong>TreeBag</strong> - An implementation of <strong>Bag</strong> that is backed by a
TreeMap. Order will be maintained among the unique representative
members.</li>
<li><strong>UnboundedFifoBuffer</strong> - Efficient implementation of Buffer
that alters the size of the buffer at runtime.</li>
</ul>
<p><b>comparators subpackage:</b></p>
<ul>
<li><strong>ComparableComparator</strong> - A Comparator that compares Comparable objects.
This Comparator is useful, for example,
for enforcing the natural order in custom implementations
of SortedSet and SortedMap.</li>
<li><strong>ComparatorChain</strong> - ComparatorChain is a Comparator that wraps one or
more Comparators in sequence. The ComparatorChain
calls each Comparator in sequence until either 1)
any single Comparator returns a non-zero result
(and that result is then returned),
or 2) the ComparatorChain is exhausted (and zero is
returned). This type of sorting is very similar
to multi-column sorting in SQL, and this class
allows Java classes to emulate that kind of behaviour
when sorting a List.</li>
<li><strong>NullComparator</strong> - A comparator that will compare nulls
to be either higher or lower than other objects.</li>
<li><strong>ReverseComparator</strong> - Reverses the order of another
comparator.</li>
<li><strong>TransformingComparator</strong> - Decorates another comparator
with transformation behavior.</li>
</ul>
<p><b>iterators subpackage:</b></p>
<ul>
<li><strong>ArrayIterator</strong> - an Iterator wrapper for arrays, including primitive arrays.</li>
<li><strong>ArrayListIterator</strong> - a ListIterator wrapper for arrays, including primitive arrays.</li>
<li><strong>CollectinIterator</strong> - Provides an ordered iterator over
the elements contained in a collection of ordered iterators.</li>
<li><strong>EnumerationIterator</strong> - Adapter to make Enumeration
instances appear to be Iterator instances.</li>
<li><strong>FilterIterator</strong> - A Proxy <code>Iterator</code> which takes a
<code>Predicate</code>
instance to filter out objects from an underlying <code>Iterator</code> instance.
Only objects for which the
specified <code>Predicate</code> evaluates to <code>true</code> are
returned.</li>
<li><strong>FilterListIterator</strong> - A proxy <code>ListIterator</code> which
takes a <code>Predicate</code> instance to filter
out objects from an underlying <code>ListIterator</code>
instance. Only objects for which the specified
<code>Predicate</code> evaluates to <code>true</code> are
returned by the iterator.</li>
<li><strong>IteratorChain</strong> - An iterator that wraps one or more
iterators.</li>
<li><strong>IteratorEnumeration</strong> - Adapter to make Iterator instances
appear to be Enumeration instances.</li>
<li><strong>ListIteratorWrapper</strong> - As the wrapped Iterator is
traversed, ListIteratorWrapper builds a LinkedList of its values,
permitting all required operations of ListIterator.</li>
<li><strong>LoopingIterator</strong> - Loops continuously around a collection.</li>
<li><strong>ObjectArrayIterator</strong> - an Iterator wrapper for Object arrays.</li>
<li><strong>ObjectArrayListIterator</strong> - a ListIterator wrapper for Object arrays.</li>
<li><strong>ProxyIterator</strong> - Delegates its methods to a proxy
instance.</li>
<li><strong>ProxyListIterator</strong> - Delegates its methods to a proxy
instance.</li>
<li><strong>SingletonIterator</strong> - An Iterator over a single
object instance.</li>
<li><strong>SingletonListIterator</strong> - A ListIterator over a single
object instance.</li>
<li><strong>TransformIterator</strong> - Uses a Transformer instance to
transform the contents of the Iterator into some other form.</li>
<li><strong>UniqueFilterIterator</strong> - A FilterIterator which only
returns "unique" Objects.</li>
</ul>
<a name="Dependencies"></a>
<h3>2. DEPENDENCIES</h3>
<p>The <em>Collections</em> package is dependent upon the following external
components for development and use:</p>
<ul>
<li><a href="http://java.sun.com/j2se">Java Development Kit</a>
(Version 1.2 or later)</li>
<li><a href="http://www.junit.org">JUnit Testing Framework</a>
(Version 3.7 or later) - for unit tests only, not required
for deployment</li>
</ul>
<a name="Release Info"></a>
<h3>3. RELEASE INFO</h3>
<p>Current Release:
<a href="http://jakarta.apache.org/builds/jakarta-commons/release/commons-collections/v2.1">Version 2.1</a>
<p>Planned Next Release: ?</p>
<a name="Committers"></a>
<h3>4. COMMITTERS</h3>
<p>The following individuals are the primary developers and maintainers of this
component. Developers who plan to use <em>Collections</em> in their own
projects are encouraged to collaborate on the future development of this
component to ensure that it continues to meet a variety of needs.</p>
<ul>
<li><a href="mailto:mas@apache.org">Michael A. Smith</a></li>
<li><a href="mailto:morgand@apache.org">Morgan Delagrange</a></li>
<li><a href="mailto:donaldp@apache.org">Peter Donald</a></li>
<li><a href="mailto:geirm@apache.org">Geir Magnusson Jr.</a></li>
<li><a href="mailto:craigmcc@apache.org">Craig McClanahan</a></li>
<li><a href="mailto:jstrachan@apache.org">James Strachan</a></li>
<li><a href="mailto:rwaldhoff@apache.org">Rodney Waldhoff</a></li>
<li><a href="mailto:jvanzyl@apache.org">Jason van Zyl</a></li>
<li><a href="mailto:bayard@apache.org">Henri Yandell</a></li>
<li><a href="mailto:pjack@apache.org">Paul Jack</a></li>
<li><a href="mailto:scolebourne@apache.org">Stephen Colebourne</a></li>
</ul>
<a name="Action Items"></a>
<h3>5. ACTION ITEMS</h3>
<p>Want to help? Here's some "to do" items the team has identified.</p>
<table border="1">
<tr>
<th width="80%">Action Item</th>
<th width="20%">Volunteer</th>
</tr>
<tr>
<td><strong>Additional Contributions</strong>. Other collection
or collection-related classes or decorators.</td>
<td align="center">&nbsp;</td>
</tr>
<tr>
<td><strong>Primitive subpackage</strong>. Complete implementations of
a collections system based on primitives.</td>
<td align="center">&nbsp;</td>
</tr>
<tr>
<td><strong>MultiMap ideas</strong>. Updates to MultiMap, maybe based on
<a href="http://www.innig.org/util/innig-util/build/javadoc">this library</a>.</td>
<td align="center">&nbsp;</td>
</tr>
<tr>
<td><strong>Additional Documentation</strong>. Create simple
User's Guide, examples, or other documentation for this package.</td>
<td align="center">&nbsp;</td>
</tr>
<tr>
<td><strong>Serializable Collections</strong>. All of the concrete
Collection and Map implementations should be properly Serializable
across all versions of the JDK. Also, decorators should be
Serializable if the underlying instance is.</td>
<td align="center">&nbsp;</td>
</tr>
<tr>
<td><strong>Fail-Fast Iterators</strong>. All concrete Collection and
Map implementations that can have fail-fast iterators should have
them. Some classes, like StaticBucketMap, cannot possibly have
fail-fast iterators, but otherwise everything else should.</td>
<td align="center">&nbsp;</td>
</tr>
<tr>
<td><strong>ArrayListIterator</strong>. A ListIterator for arrays</td>
</tr>
<tr>
<td><strong>LoopingListIterator</strong>. A ListIterator similar to LoopingIterator</td>
</tr>
<tr>
<td><strong>Standard Constructors</strong>. All concrete Collection and
Map implementations should have the standard copy and no-argument
constructors.</td>
<td align="center">&nbsp;</td>
</tr>
<tr>
<td><strong>Additional Unit Tests</strong>. Create generic unit tests
for SortedSet and SortedMap.</td>
<td align="center">&nbsp;</td>
</tr>
</table>
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