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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.collections;
import java.util.Collection;
import java.util.Iterator;
/**
* Utility class which is useful when implementing <code>Comparable</code> and one needs to
* compare Collections of Comparables as instance variables.
*
* @author Einar M R Rosenvinge
*/
public class CollectionComparator {
/**
* Compare the arguments. Shorter Collections are always considered
* smaller than longer Collections. For Collections of equal lengths, the elements
* are compared one-by-one. Whenever two corresponding elements in the
* two Collections are non-equal, the method returns. If all elements at
* corresponding positions in the two Collections are equal, the Collections
* are considered equal.
*
* @param first a Collection of Comparables to be compared
* @param second a Collection of Comparables to be compared
* @return 0 if the arguments are equal, -1 if the first argument is smaller, 1 if the second argument is smaller
* @throws NullPointerException if any of the arguments are null
*/
@SuppressWarnings({"rawtypes", "unchecked"})
public static int compare(Collection<? extends Comparable> first, Collection<? extends Comparable> second) {
if (first.size() < second.size()) {
return -1;
}
if (first.size() > second.size()) {
return 1;
}
//sizes are equal, compare contents
Iterator<? extends Comparable> firstIt = first.iterator();
Iterator<? extends Comparable> secondIt = second.iterator();
while (firstIt.hasNext()) {
// FIXME: unchecked casting
Comparable itemFirst = firstIt.next();
Comparable itemSecond = secondIt.next();
int comp = itemFirst.compareTo(itemSecond);
if (comp != 0) {
return comp;
}
//values are equal, continue...
}
//we haven't returned yet; contents must be equal:
return 0;
}
}
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