io.trino.execution.scheduler.ResettableRandomizedIterator Maven / Gradle / Ivy
/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.trino.execution.scheduler;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.concurrent.ThreadLocalRandom;
public class ResettableRandomizedIterator
implements Iterator
{
private final List list;
private int position;
public ResettableRandomizedIterator(Collection elements)
{
this.list = new ArrayList<>(elements);
}
public void reset()
{
position = 0;
}
@Override
public boolean hasNext()
{
return position < list.size();
}
@Override
public T next()
{
if (!hasNext()) {
throw new NoSuchElementException();
}
int position = ThreadLocalRandom.current().nextInt(this.position, list.size());
T result = list.set(position, list.get(this.position));
list.set(this.position, result);
this.position++;
return result;
}
}