platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/UserDataInterner.java

/*
 * Copyright 2000-2014 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 com.intellij.openapi.vfs.newvfs.impl;

import com.intellij.util.ConcurrencyUtil;
import com.intellij.util.containers.ConcurrentWeakHashMap;
import com.intellij.util.keyFMap.KeyFMap;
import com.intellij.util.keyFMap.OneElementFMap;
import org.jetbrains.annotations.NotNull;

import java.nio.charset.Charset;

/**
 * @author peter
 */
class UserDataInterner {
  private static final ConcurrentWeakHashMap<OneElementFMap, OneElementFMap> ourCache = new ConcurrentWeakHashMap<OneElementFMap, OneElementFMap>();

  static KeyFMap internUserData(@NotNull KeyFMap map) {
    if (map instanceof OneElementFMap && shouldIntern((OneElementFMap)map)) {
      return ConcurrencyUtil.cacheOrGet(ourCache, (OneElementFMap)map, (OneElementFMap)map);
    }
    return map;
  }

  private static boolean shouldIntern(OneElementFMap map) {
    Object value = map.getValue();
    return value instanceof Enum || value instanceof Boolean || value instanceof Charset;
  }
}