infinispan.com.mchange.v1.util.WrapperIterator Maven / Gradle / Ivy
/*
* Distributed as part of mchange-commons-java 0.2.7
*
* Copyright (C) 2014 Machinery For Change, Inc.
*
* Author: Steve Waldman
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of EITHER:
*
* 1) The GNU Lesser General Public License (LGPL), version 2.1, as
* published by the Free Software Foundation
*
* OR
*
* 2) The Eclipse Public License (EPL), version 1.0
*
* You may choose which license to accept if you wish to redistribute
* or modify this work. You may offer derivatives of this work
* under the license you have chosen, or you may provide the same
* choice of license which you have been offered here.
*
* 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.
*
* You should have received copies of both LGPL v2.1 and EPL v1.0
* along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
* If not, the text of these licenses are currently available at
*
* LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php
*
*/
package com.mchange.v1.util;
import java.util.*;
import com.mchange.v1.util.DebugUtils;
/**
* This implementation does not yet support removes once hasNext() has
* been called... will add if necessary.
*/
public abstract class WrapperIterator implements Iterator
{
protected final static Object SKIP_TOKEN = new Object();
final static boolean DEBUG = true;
Iterator inner;
boolean supports_remove;
Object lastOut = null;
Object nextOut = SKIP_TOKEN;
public WrapperIterator(Iterator inner, boolean supports_remove)
{
this.inner = inner;
this.supports_remove = supports_remove;
}
public WrapperIterator(Iterator inner)
{ this( inner, false ); }
public boolean hasNext()
{
findNext();
return nextOut != SKIP_TOKEN;
}
private void findNext()
{
if (nextOut == SKIP_TOKEN)
{
while (inner.hasNext() && nextOut == SKIP_TOKEN)
this.nextOut = transformObject( inner.next() );
}
}
public Object next()
{
findNext();
if (nextOut != SKIP_TOKEN)
{
lastOut = nextOut;
nextOut = SKIP_TOKEN;
}
else
throw new NoSuchElementException();
//postcondition
if (DEBUG)
DebugUtils.myAssert( nextOut == SKIP_TOKEN && lastOut != SKIP_TOKEN );
return lastOut;
}
public void remove()
{
if (supports_remove)
{
if (nextOut != SKIP_TOKEN)
throw new UnsupportedOperationException(this.getClass().getName() +
" cannot support remove after" +
" hasNext() has been called!");
if (lastOut != SKIP_TOKEN)
inner.remove();
else
throw new NoSuchElementException();
}
else
throw new UnsupportedOperationException();
}
/**
* return SKIP_TOKEN to indicate an object should be
* skipped, i.e., not exposed as part of the iterator.
* (we don't use null, because we want to support iterators
* over null-accepting Collections.)
*/
protected abstract Object transformObject(Object o);
}