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/*******************************************************************************
* Copyright (c) 2005, 2008 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.utility.internal.iterators;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import org.eclipse.jpt.utility.internal.StringTools;
/**
* A <code>CompositeListIterator</code> wraps a list
* of <code>ListIterator</code>s and makes them appear to be a single
* <code>ListIterator</code>.
*/
public class CompositeListIterator<E>
implements ListIterator<E>
{
private final ListIterator<? extends ListIterator<E>> iterators;
private ListIterator<E> nextIterator;
private int nextIndex;
/**
* true if "next" was last returned; false if "previous" was last returned;
* this determines the effect of remove(Object) on nextIndex
*/
private boolean nextReturned;
private ListIterator<E> lastIteratorToReturnElement;
/**
* Construct a list iterator with the specified list of list iterators.
*/
public CompositeListIterator(List<? extends ListIterator<E>> iterators) {
this(iterators.listIterator());
}
/**
* Construct a list iterator with the specified list of list iterators.
*/
public CompositeListIterator(ListIterator<? extends ListIterator<E>> iterators) {
super();
this.iterators = iterators;
this.nextIndex = 0;
this.nextReturned = false;
}
/**
* Construct a list iterator with the specified object prepended
* to the specified iterator.
*/
@SuppressWarnings("unchecked")
public CompositeListIterator(E object, ListIterator<E> iterator) {
this(new SingleElementListIterator<E>(object), iterator);
}
/**
* Construct a list iterator with the specified object appended
* to the specified iterator.
*/
@SuppressWarnings("unchecked")
public CompositeListIterator(ListIterator<E> iterator, E object) {
this(iterator, new SingleElementListIterator<E>(object));
}
/**
* Construct a list iterator with the specified list iterators.
*/
public CompositeListIterator(ListIterator<E>... iterators) {
this(new ArrayListIterator<ListIterator<E>>(iterators));
}
public void add(E o) {
this.checkNextIterator();
this.nextIterator.add(o);
this.nextIndex++;
}
public boolean hasNext() {
try {
this.loadNextIterator();
} catch (NoSuchElementException ex) {
// this occurs if there are no iterators at all
return false;
}
return this.nextIterator.hasNext();
}
public boolean hasPrevious() {
try {
this.loadPreviousIterator();
} catch (NoSuchElementException ex) {
// this occurs if there are no iterators at all
return false;
}
return this.nextIterator.hasPrevious();
}
public E next() {
this.loadNextIterator();
E result = this.nextIterator.next();
// the statement above will throw a NoSuchElementException
// if the current iterator is at the end of the line;
// so if we get here, we can set the 'lastIteratorToReturnElement'
this.lastIteratorToReturnElement = this.nextIterator;
this.nextIndex++;
this.nextReturned = true;
return result;
}
public int nextIndex() {
return this.nextIndex;
}
public E previous() {
this.loadPreviousIterator();
E result = this.nextIterator.previous();
// the statement above will throw a NoSuchElementException
// if the current iterator is at the end of the line;
// so if we get here, we can set the 'lastIteratorToReturnElement'
this.lastIteratorToReturnElement = this.nextIterator;
this.nextIndex--;
this.nextReturned = false;
return result;
}
public int previousIndex() {
return this.nextIndex - 1;
}
public void remove() {
if (this.lastIteratorToReturnElement == null) {
throw new IllegalStateException();
}
this.lastIteratorToReturnElement.remove();
if (this.nextReturned) {
// decrement the index because the "next" element has moved forward in the list
this.nextIndex--;
}
}
public void set(E e) {
if (this.lastIteratorToReturnElement == null) {
throw new IllegalStateException();
}
this.lastIteratorToReturnElement.set(e);
}
/**
* Load 'nextIterator' with the first iterator that <code>hasNext()</code>
* or the final iterator if all the elements have already been retrieved.
*/
private void loadNextIterator() {
this.checkNextIterator();
while (( ! this.nextIterator.hasNext()) && this.iterators.hasNext()) {
this.nextIterator = this.iterators.next();
}
}
/**
* Load 'nextIterator' with the first iterator that <code>hasPrevious()</code>
* or the first iterator if all the elements have already been retrieved.
*/
private void loadPreviousIterator() {
this.checkNextIterator();
while (( ! this.nextIterator.hasPrevious()) && this.iterators.hasPrevious()) {
this.nextIterator = this.iterators.previous();
}
}
/**
* If 'nextIterator' is null, load it with the first iterator.
*/
private void checkNextIterator() {
if (this.nextIterator == null) {
this.nextIterator = this.iterators.next();
}
}
@Override
public String toString() {
return StringTools.buildToStringFor(this, this.iterators);
}
}
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