Mega Code Archive
Create singleton Iterator
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/*
GNU LESSER GENERAL PUBLIC LICENSE
Copyright (C) 2006 The Lobo Project
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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 library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Contact info: lobochief@users.sourceforge.net
*/
/*
* Created on Jun 9, 2005
*/
import java.util.*;
/**
* @author J. H. S.
*/
class CollectionUtilities {
/**
*
*/
private CollectionUtilities() {
super();
}
public static Enumeration getIteratorEnumeration(final Iterator i) {
return new Enumeration() {
public boolean hasMoreElements() {
return i.hasNext();
}
public Object nextElement() {
return i.next();
}
};
}
public static Iterator iteratorUnion(final Iterator[] iterators) {
return new Iterator() {
private int iteratorIndex = 0;
private Iterator current = iterators.length > 0 ? iterators[0] : null;
public boolean hasNext() {
for(;;) {
if(current == null) {
return false;
}
if(current.hasNext()) {
return true;
}
iteratorIndex++;
current = iteratorIndex >= iterators.length ? null : iterators[iteratorIndex];
}
}
public Object next() {
for(;;) {
if(this.current == null) {
throw new NoSuchElementException();
}
try {
return this.current.next();
} catch(NoSuchElementException nse) {
this.iteratorIndex++;
this.current = this.iteratorIndex >= iterators.length ? null : iterators[this.iteratorIndex];
}
}
}
public void remove() {
if(this.current == null) {
throw new NoSuchElementException();
}
this.current.remove();
}
};
}
public static Collection reverse(Collection collection) {
LinkedList newCollection = new LinkedList();
Iterator i = collection.iterator();
while(i.hasNext()) {
newCollection.addFirst(i.next());
}
return newCollection;
}
public static Iterator singletonIterator(final Object item) {
return new Iterator() {
private boolean gotItem = false;
public boolean hasNext() {
return !this.gotItem;
}
public Object next() {
if(this.gotItem) {
throw new NoSuchElementException();
}
this.gotItem = true;
return item;
}
public void remove() {
if(!this.gotItem) {
this.gotItem = true;
}
else {
throw new NoSuchElementException();
}
}
};
}
}
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