001    /*
002     * Copyright 2010-2014 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.jet.utils;
018    
019    import com.intellij.util.containers.hash.EqualityPolicy;
020    import com.intellij.util.containers.hash.LinkedHashMap;
021    import org.jetbrains.annotations.NotNull;
022    
023    import java.util.Map;
024    import java.util.Set;
025    
026    public class HashSetUtil {
027        @NotNull
028        public static <T> Set<T> linkedHashSet(@NotNull Set<T> set,  @NotNull EqualityPolicy<T> policy) {
029            // this implementation of LinkedHashMap doesn't admit nulls as values
030            Map<T, String> map = new LinkedHashMap<T, String>(policy);
031            for (T t : set) {
032                map.put(t, "");
033            }
034            return map.keySet();
035        }
036    }