001    /*
002     * Copyright 2010-2016 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.Collection;
025    import java.util.Map;
026    import java.util.Set;
027    
028    public class HashSetUtil {
029        @NotNull
030        public static <T> Set<T> linkedHashSet(@NotNull Collection<T> set,  @NotNull EqualityPolicy<T> policy) {
031            // this implementation of LinkedHashMap doesn't admit nulls as values
032            Map<T, String> map = new LinkedHashMap<T, String>(policy);
033            for (T t : set) {
034                map.put(t, "");
035            }
036            return map.keySet();
037        }
038    
039        @NotNull
040        public static <T> Set<T> symmetricDifference(@NotNull Set<T> set1, @NotNull Set<T> set2) {
041            Set<T> intersection = new HashSet<T>();
042            intersection.addAll(set1);
043            intersection.retainAll(set2);
044            Set<T> result = new HashSet<T>();
045            result.addAll(set1);
046            result.addAll(set2);
047            result.removeAll(intersection);
048    
049            return result;
050        }
051    }