Iterator Utils
/*
* Distributed as part of debuggen v.0.1.0
*
* Copyright (C) 2005 Machinery For Change, Inc.
*
* Author: Steve Waldman <swaldman@mchange.com>
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 2.1, as
* published by the Free Software Foundation.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this software; see the file LICENSE. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*/
import java.util.*;
import java.lang.reflect.Array;
public final class IteratorUtils
{
public final static Iterator EMPTY_ITERATOR = new Iterator()
{
public boolean hasNext()
{ return false; }
public Object next()
{ throw new NoSuchElementException(); }
public void remove()
{ throw new IllegalStateException(); }
};
public static Iterator oneElementUnmodifiableIterator(final Object elem)
{
return new Iterator()
{
boolean shot = false;
public boolean hasNext() { return (!shot); }
public Object next()
{
if (shot)
throw new NoSuchElementException();
else
{
shot = true;
return elem;
}
}
public void remove()
{ throw new UnsupportedOperationException("remove() not supported."); }
};
}
public static boolean equivalent(Iterator ii, Iterator jj)
{
while (true)
{
boolean ii_hasnext = ii.hasNext();
boolean jj_hasnext = jj.hasNext();
if (ii_hasnext ^ jj_hasnext)
return false;
else if (ii_hasnext)
{
Object iiNext = ii.next();
Object jjNext = jj.next();
if (iiNext == jjNext)
continue;
else if (iiNext == null)
return false;
else if (!iiNext.equals(jjNext))
return false;
}
else return true;
}
}
public static ArrayList toArrayList(Iterator ii, int initial_capacity)
{
ArrayList out = new ArrayList(initial_capacity);
while (ii.hasNext())
out.add(ii.next());
return out;
}
/**
* Fills an array with the contents of an iterator. If the array is too small,
* it will contain the first portion of the iterator. If the array can contain
* more elements than the iterator, extra elements are left untouched, unless
* null_terminate is set to true, in which case the element immediately following
* the last from the iterator is set to null. (This method is intended to make
* it easy to implement Collection.toArray(Object[] oo) methods...
*
* @param null_terminate iff there is extra space in the array, set the element
* immediately after the last from the iterator to null.
*/
public static void fillArray(Iterator ii, Object[] fillMe, boolean null_terminate)
{
int i = 0;
int len = fillMe.length;
while ( i < len && ii.hasNext() )
fillMe[ i++ ] = ii.next();
if (null_terminate && i < len)
fillMe[i] = null;
}
public static void fillArray(Iterator ii, Object[] fillMe)
{ fillArray( ii, fillMe, false); }
/**
* @param null_terminate iff there is extra space in the array, set the element
* immediately after the last from the iterator to null.
*/
public static Object[] toArray(Iterator ii, int array_size, Class componentClass, boolean null_terminate)
{
Object[] out = (Object[]) Array.newInstance( componentClass, array_size );
fillArray(ii, out, null_terminate);
return out;
}
public static Object[] toArray(Iterator ii, int array_size, Class componentClass)
{ return toArray( ii, array_size, componentClass, false ); }
/**
* Designed to help implement Collection.toArray(Object[] )methods... does
* the right thing if you can express an iterator and know the size of your
* Collection.
*/
public static Object[] toArray(Iterator ii, int ii_size, Object[] maybeFillMe)
{
if (maybeFillMe.length >= ii_size)
{
fillArray( ii, maybeFillMe, true );
return maybeFillMe;
}
else
{
Class componentType = maybeFillMe.getClass().getComponentType();
return toArray( ii, ii_size, componentType );
}
}
private IteratorUtils()
{}
}
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