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Hibernate's core ORM functionality
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* License: GNU Lesser General Public License (LGPL), version 2.1 or later.
* See the lgpl.txt file in the root directory or .
*/
package org.hibernate.internal.util.collections;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
/**
* An Iterator implementation that wraps other Iterators, and presents them all as one
* continuous Iterator. When any method from Iterator is called, we delegate to each
* wrapped Iterator in turn until all wrapped Iterators are exhausted.
*
* @author Gavine King
* @author Steve Ebersole
*/
public class JoinedIterator implements Iterator {
private Iterator[] wrappedIterators;
private int currentIteratorIndex;
private Iterator currentIterator;
private Iterator lastUsedIterator;
@SuppressWarnings("unchecked")
public JoinedIterator(List> wrappedIterators) {
this( wrappedIterators.toArray( new Iterator[ wrappedIterators.size() ]) );
}
public JoinedIterator(Iterator... iteratorsToWrap) {
if( iteratorsToWrap == null ) {
throw new NullPointerException( "Iterators to join were null" );
}
this.wrappedIterators = iteratorsToWrap;
}
public boolean hasNext() {
updateCurrentIterator();
return currentIterator.hasNext();
}
public T next() {
updateCurrentIterator();
return currentIterator.next();
}
public void remove() {
updateCurrentIterator();
lastUsedIterator.remove();
}
// call this before any Iterator method to make sure that the current Iterator
// is not exhausted
protected void updateCurrentIterator() {
if ( currentIterator == null ) {
if( wrappedIterators.length == 0 ) {
currentIterator = Collections.emptyList().iterator();
}
else {
currentIterator = wrappedIterators[0];
}
// set last used iterator here, in case the user calls remove
// before calling hasNext() or next() (although they shouldn't)
lastUsedIterator = currentIterator;
}
while (! currentIterator.hasNext() && currentIteratorIndex < wrappedIterators.length - 1) {
currentIteratorIndex++;
currentIterator = wrappedIterators[currentIteratorIndex];
}
}
}