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Iterators2.java
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Iterators2.java
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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.common.collect;
import com.google.common.collect.Iterators;
import com.google.common.collect.PeekingIterator;
import com.google.common.collect.UnmodifiableIterator;
import java.util.Comparator;
import java.util.Iterator;
public enum Iterators2 {
;
/** Remove duplicated elements from an iterator over sorted content. */
public static <T> Iterator<T> deduplicateSorted(Iterator<? extends T> iterator, final Comparator<? super T> comparator) {
final PeekingIterator<T> it = Iterators.peekingIterator(iterator);
return new UnmodifiableIterator<T>() {
@Override
public boolean hasNext() {
return it.hasNext();
}
@Override
public T next() {
final T ret = it.next();
while (it.hasNext() && comparator.compare(ret, it.peek()) == 0) {
it.next();
}
assert !it.hasNext() || comparator.compare(ret, it.peek()) < 0 : "iterator is not sorted: " + ret + " > " + it.peek();
return ret;
}
};
}
/** Return a merged view over several iterators, optionally deduplicating equivalent entries. */
public static <T> Iterator<T> mergeSorted(Iterable<Iterator<? extends T>> iterators, Comparator<? super T> comparator, boolean deduplicate) {
Iterator<T> it = Iterators.mergeSorted(iterators, comparator);
if (deduplicate) {
it = deduplicateSorted(it, comparator);
}
return it;
}
}