/*---------------------------------------------------------------------------*\
$Id: 1a7ef257e47a826015f6f3c52854f8409b98783f $
---------------------------------------------------------------------------
This software is released under a BSD-style license:
Copyright (c) 2004-2007 Brian M. Clapper. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. The end-user documentation included with the redistribution, if any,
must include the following acknowlegement:
"This product includes software developed by Brian M. Clapper
(bmc@clapper.org, http://www.clapper.org/bmc/). That software is
copyright (c) 2004-2007 Brian M. Clapper."
Alternately, this acknowlegement may appear in the software itself,
if wherever such third-party acknowlegements normally appear.
3. Neither the names "clapper.org", "clapper.org Java Utility Library",
nor any of the names of the project contributors may be used to
endorse or promote products derived from this software without prior
written permission. For written permission, please contact
bmc@clapper.org.
4. Products derived from this software may not be called "clapper.org
Java Utility Library", nor may "clapper.org" appear in their names
without prior written permission of Brian M. Clapper.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
NO EVENT SHALL BRIAN M. CLAPPER BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\*---------------------------------------------------------------------------*/
package org.clapper.util.misc;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Collection;
import java.util.Enumeration;
import java.util.NoSuchElementException;
/**
* The MultiIterator class provides a way to iterate over
* multiple Collection, Enumeration and Iterator
* objects at once. You instantiate a MultiIterator object and add
* one or more Collection, Enumeration or
* Iterator objects to it; when you use the iterator, it iterates
* over the contents of each contained composite object, one by one, in the
* order they were added to the MultiIterator. When the iterator
* reaches the end of one object's contents, it moves on to the next
* object, until no more composite objects are left.
*
* @see java.util.Iterator
* @see java.util.Enumeration
* @see java.util.Collection
*
* @version $Revision$
*
* @author Copyright © 2004-2007 Brian M. Clapper
*/
public class MultiIterator implements Iterator, Iterable
{
/*----------------------------------------------------------------------*\
Private Data Elements
\*----------------------------------------------------------------------*/
/**
* The underlying objects being iterated over, stored in a Collection
*/
private Collection> aggregation = new ArrayList>();
/**
* The iterator for the list of aggregation
*/
private Iterator> aggregationIterator = null;
/**
* The iterator for the current object
*/
private Iterator it = null;
/*----------------------------------------------------------------------*\
Constructor
\*----------------------------------------------------------------------*/
/**
* Allocate a new MultiIterator object.
*/
public MultiIterator()
{
// Nothing to do
}
/**
* Allocate a new MultiIterator object that will iterate, in
* turn, over the contents of each Collection in the supplied
* array.
*
* @param array The Collections over which to iterate
*
* @see #addCollection(Collection)
*/
public MultiIterator (Collection array[])
{
for (int i = 0; i < array.length; i++)
aggregation.add (array[i].iterator());
}
/**
* Allocate a new MultiIterator object that will iterate, in
* turn, over the contents of each Collection in the supplied
* Collection
*
* @param coll A Collection of Collection objects
*
* @see #addCollection(Collection)
*/
public MultiIterator (Collection> coll)
{
for (Iterator> iterator = coll.iterator();
iterator.hasNext(); )
{
aggregation.add (iterator.next().iterator());
}
}
/*----------------------------------------------------------------------*\
Public Methods
\*----------------------------------------------------------------------*/
/**
* Add a Collection to the end of the list of composite
* objects being iterated over. It's safe to call this method while
* iterating, as long as you haven't reached the end of the last
* composite object currently in the iterator.
*
* Note: This method is simply shorthand for:
*
*
* addIterator (collection.iterator());
*
*
* @param collection The Collection to add.
*
* @see #addIterator
* @see #addEnumeration
*/
public void addCollection (Collection collection)
{
aggregation.add (collection.iterator());
}
/**
* Add an Iterator to the end of the list of composite objects
* being iterated over. It's safe to call this method while iterating,
* as long as you haven't reached the end of the last composite object
* currently in the iterator.
*
* @param iterator The Iterator to add.
*
* @see #addCollection
* @see #addEnumeration
*/
public void addIterator (Iterator iterator)
{
aggregation.add (iterator);
}
/**
* Add an Enumeration to the end of the list of composite
* objects being iterated over. It's safe to call this method while
* iterating, as long as you haven't reached the end of the last
* composite object currently in the iterator.
*
* Note: This method is simply shorthand for:
*
*
* addIterator (new EnumerationIterator (enumeration));
*
*
* @param enumeration The Enumeration to add.
*
* @see #addCollection
* @see #addIterator
* @see EnumerationIterator
*/
public void addEnumeration (Enumeration enumeration)
{
aggregation.add (new EnumerationIterator (enumeration));
}
/**
* Determine whether the underlying Iterator has more
* elements.
*
* @return true if and only if a call to
* nextElement() will return an element,
* false otherwise.
*
* @see #next
*/
public boolean hasNext()
{
boolean someLeft = false;
checkIterator();
if (it != null)
someLeft = it.hasNext();
return someLeft;
}
/**
* Returns this iterator. Necessary for the Iterable interface.
*
* @return this object
*/
public Iterator iterator()
{
return this;
}
/**
* Get the next element from the underlying array.
*
* @return the next element from the underlying array
*
* @throws NoSuchElementException No more elements exist
*
* @see java.util.Iterator#next
*/
public T next() throws NoSuchElementException
{
T result = null;
checkIterator();
if (it != null)
result = it.next();
return result;
}
/**
* Remove the object most recently extracted from the iterator.
* The object is removed from whatever underlying Collection
* is currently being traversed.
*/
public void remove()
{
if (it != null)
it.remove();
}
/*----------------------------------------------------------------------*\
Private Methods
\*----------------------------------------------------------------------*/
private synchronized void checkIterator()
{
if (aggregationIterator == null)
{
it = null;
aggregationIterator = aggregation.iterator();
if (aggregationIterator.hasNext())
it = aggregationIterator.next();
}
while ( (it != null) && (! it.hasNext()) )
{
if (! aggregationIterator.hasNext())
it = null;
else
it = aggregationIterator.next();
}
}
}
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