Minor, inline HashSetUtil#symmetricDifference

compiler/util/src/org/jetbrains/kotlin/utils/HashSetUtil.java

@@ -1,37 +0,0 @@
-/*
- * Copyright 2010-2016 JetBrains s.r.o.
- *
- * Licensed 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.jetbrains.kotlin.utils;
-
-import com.intellij.util.containers.hash.HashSet;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.Set;
-
-public class HashSetUtil {
-    @NotNull
-    public static <T> Set<T> symmetricDifference(@NotNull Set<T> set1, @NotNull Set<T> set2) {
-        Set<T> intersection = new HashSet<T>();
-        intersection.addAll(set1);
-        intersection.retainAll(set2);
-        Set<T> result = new HashSet<T>();
-        result.addAll(set1);
-        result.addAll(set2);
-        result.removeAll(intersection);
-
-        return result;
-    }
-}