/*
* Copyright 2010-2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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 com.amazonaws.test.util;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
/**
* This class includes some utility methods for comparing two unordered
* collections.
*/
public class UnorderedCollectionComparator {
/**
* Compares two unordered lists of the same type.
*/
public static <T> boolean equalUnorderedCollections(
Collection<T> colA, Collection<T> colB) {
return equalUnorderedCollections(colA, colB, new CrossTypeComparator<T, T>() {
@Override
public boolean equals(T a, T b) {
return (a == null && b == null)
|| a.equals(b);
}
});
}
/**
* Compares two unordered lists of different types, using the specified
* cross-type comparator. Null collections are treated as empty ones.
* Naively implemented using N(n^2) algorithm.
*/
public static <A, B> boolean equalUnorderedCollections(
Collection<A> colA, Collection<B> colB,
final CrossTypeComparator<A, B> comparator) {
if (colA == null || colB == null){
if ( (colA == null || colA.isEmpty())
&& (colB == null || colB.isEmpty()) ) {
return true;
} else {
return false;
}
}
// Add all elements into sets to remove duplicates.
Set<A> setA = new HashSet<A>();
setA.addAll(colA);
Set<B> setB = new HashSet<B>();
setB.addAll(colB);
if ( setA.size() != setB.size() ){
return false;
}
for (A a : setA) {
boolean foundA = false;
for (B b : setB) {
if (comparator.equals(a, b)) {
foundA = true;
break;
}
}
if ( !foundA ) {
return false;
}
}
return true;
}
/**
* A simple interface that attempts to compare objects of two different types
*/
public static interface CrossTypeComparator<A, B> {
/**
* @return True if a and b should be treated as equal.
*/
public boolean equals(A a, B b);
}
}