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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;
/**
* A JoinedIterable is an Iterable that wraps a number of Iterables.
*
* This class makes multiple iterables look like one to the caller.
* When any method from the Iterator interface is called on the
* Iterator object returned by {@link #iterator()}, the JoinedIterable
* will delegate to a single underlying Iterator. The JoinedIterable will
* invoke the iterator on each Iterable, in sequence, until all Iterators
* are exhausted.
*
* @author Gail Badner (adapted from JoinedIterator)
*/
public class JoinedIterable implements Iterable {
private final TypeSafeJoinedIterator iterator;
public JoinedIterable(List> iterables) {
if ( iterables == null ) {
throw new NullPointerException( "Unexpected null iterables argument" );
}
iterator = new TypeSafeJoinedIterator( iterables );
}
public Iterator iterator() {
return iterator;
}
private static class TypeSafeJoinedIterator implements Iterator {
// wrapped iterators
private List> iterables;
// index of current iterator in the wrapped iterators array
private int currentIterableIndex;
// the current iterator
private Iterator currentIterator;
// the last used iterator
private Iterator lastUsedIterator;
public TypeSafeJoinedIterator(List> iterables) {
this.iterables = iterables;
}
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
@SuppressWarnings( {"unchecked"})
protected void updateCurrentIterator() {
if ( currentIterator == null) {
if( iterables.size() == 0 ) {
currentIterator = Collections.emptyIterator();
}
else {
currentIterator = iterables.get( 0 ).iterator();
}
// 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() && currentIterableIndex < iterables.size() - 1) {
currentIterableIndex++;
currentIterator = iterables.get( currentIterableIndex ).iterator();
}
}
}
}