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    package org.jetbrains.kotlin.util.userDataHolder.keyFMap;
017    
018    import com.intellij.openapi.util.Key;
019    import org.jetbrains.annotations.NotNull;
020    import org.jetbrains.annotations.Nullable;
021    
022    /**
023     * An immutable map optimized for storing few {@link Key} entries with relatively rare updates
024     * To construct a map, start with {@link KeyFMap#EMPTY_MAP} and call {@link #plus} and {@link #minus}
025     */
026    public interface KeyFMap {
027      KeyFMap EMPTY_MAP = new EmptyFMap();
028    
029      @NotNull
030      <V> KeyFMap plus(@NotNull Key<V> key, @NotNull V value);
031      @NotNull
032      KeyFMap minus(@NotNull Key<?> key);
033    
034      @Nullable
035      <V> V get(@NotNull Key<V> key);
036    
037      @NotNull
038      Key[] getKeys();
039    
040      String toString();
041    
042      boolean isEmpty();
043    }