overflowdb.util.MultiIterator Maven / Gradle / Ivy
package overflowdb.util;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
/**
* Subclass-safe variant of MultiIterator from Tinkerpop
*/
public final class MultiIterator implements Iterator, Serializable {
public static MultiIterator from(Iterator... iterators) {
MultiIterator result = new MultiIterator<>();
for (Iterator iter : iterators) result.addIterator(iter);
return result;
}
private final List> iterators = new ArrayList<>();
private int current = 0;
public void addIterator(final Iterator iterator) {
this.iterators.add(iterator);
}
@Override
public boolean hasNext() {
if (this.current >= this.iterators.size())
return false;
Iterator currentIterator = this.iterators.get(this.current);
while (true) {
if (currentIterator.hasNext()) {
return true;
} else {
this.current++;
if (this.current >= iterators.size())
break;
currentIterator = iterators.get(this.current);
}
}
return false;
}
@Override
public void remove() {
this.iterators.get(this.current).remove();
}
@Override
public T next() {
if (this.iterators.isEmpty()) throw new NoSuchElementException();
Iterator currentIterator = iterators.get(this.current);
while (true) {
if (currentIterator.hasNext()) {
return currentIterator.next();
} else {
this.current++;
if (this.current >= iterators.size())
break;
currentIterator = iterators.get(current);
}
}
throw new NoSuchElementException();
}
public void clear() {
this.iterators.clear();
this.current = 0;
}
}