org.infinispan.commons.util.ConcatIterator Maven / Gradle / Ivy
package org.infinispan.commons.util;
import java.util.Iterator;
/**
* Iterator that concatenates a bunch of iterables into 1 big iterator. Each iterable is retrieved lazily as requested.
* Note that if any of the produced iterators from the iterable implement {@link CloseableIterator} they will be closed
* when iterated upon fully or the last used iterator will be close when this iterator this closed.
*
* Removal is implemented and will invoke remove on the last used iterator
* @author wburns
* @since 9.3
*/
public class ConcatIterator extends AbstractIterator implements CloseableIterator {
private final Iterator> iterables;
private Iterator currentIterator;
public ConcatIterator(Iterable> iterableIterables) {
this.iterables = iterableIterables.iterator();
if (iterables.hasNext()) {
// Always initialize current iterator
currentIterator = iterables.next().iterator();
}
}
@Override
protected E getNext() {
E next = null;
if (currentIterator != null) {
while (next == null) {
if (currentIterator.hasNext()) {
next = currentIterator.next();
} else {
closeIterator(currentIterator);
if (iterables.hasNext()) {
currentIterator = iterables.next().iterator();
} else {
// None more left
currentIterator = null;
break;
}
}
}
}
return next;
}
@Override
public void close() {
closeIterator(currentIterator);
}
@Override
public void remove() {
if (currentIterator != null) {
currentIterator.remove();
}
}
private static void closeIterator(Iterator iter) {
if (iter instanceof CloseableIterator) {
((CloseableIterator) iter).close();
}
}
}