001    /*
002     * Copyright 2010-2015 JetBrains s.r.o.
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package org.jetbrains.kotlin.utils;
018    
019    import com.intellij.util.containers.hash.EqualityPolicy;
020    import com.intellij.util.containers.hash.HashSet;
021    import com.intellij.util.containers.hash.LinkedHashMap;
022    import org.jetbrains.annotations.NotNull;
023    
024    import java.util.Map;
025    import java.util.Set;
026    
027    public class HashSetUtil {
028        @NotNull
029        public static <T> Set<T> linkedHashSet(@NotNull Set<T> set,  @NotNull EqualityPolicy<T> policy) {
030            // this implementation of LinkedHashMap doesn't admit nulls as values
031            Map<T, String> map = new LinkedHashMap<T, String>(policy);
032            for (T t : set) {
033                map.put(t, "");
034            }
035            return map.keySet();
036        }
037    
038        @NotNull
039        public static <T> Set<T> symmetricDifference(@NotNull Set<T> set1, @NotNull Set<T> set2) {
040            Set<T> intersection = new HashSet<T>();
041            intersection.addAll(set1);
042            intersection.retainAll(set2);
043            Set<T> result = new HashSet<T>();
044            result.addAll(set1);
045            result.addAll(set2);
046            result.removeAll(intersection);
047    
048            return result;
049        }
050    }