src/android/src/com/google/android/inputmethod/japanese/util/LeastRecentlyUsedCacheMap.java

// Copyright 2010-2015, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package org.mozc.android.inputmethod.japanese.util;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Simple LRU cache implementation based on LinkedHashMap.
 *
 */
public class LeastRecentlyUsedCacheMap<K, V> extends LinkedHashMap<K, V> {
  private final int maxEntrySize;

  /**
   * @param maxEntrySize the number of elements this cache should hold.
   */
  public LeastRecentlyUsedCacheMap(int maxEntrySize) {
    // We don't need to resize because if the number of elements is limited.
    // Thus, set factor to 1.
    super(maxEntrySize + maxEntrySize / 2, 1f, true);
    if (maxEntrySize <= 0) {
      throw new IllegalArgumentException("maxEntrySize should be positive value: " + maxEntrySize);
    }
    this.maxEntrySize = maxEntrySize;
  }

  @Override
  protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
    return size() > maxEntrySize;
  }
}