CapacityLruLinkedHashMap.java

/*
 * This file is part of Waarp Project (named also Waarp or GG).
 *
 *  Copyright (c) 2019, Waarp SAS, and individual contributors by the @author
 *  tags. See the COPYRIGHT.txt in the distribution for a full listing of
 * individual contributors.
 *
 *  All Waarp Project is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * Waarp is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along with
 * Waarp . If not, see <http://www.gnu.org/licenses/>.
 */
package org.waarp.common.lru;

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

/**
 * Capacity based LRU version of LinkedHashMap
 *
 * @author Damian Momot
 */
class CapacityLruLinkedHashMap<K, V> extends LinkedHashMap<K, V> {
  /**
   *
   */
  private static final long serialVersionUID = -5064888079959689619L;

  private final int capacity;

  /**
   * Creates LRU LinkedHashMap
   *
   * @param capacity
   * @param initialCapacity
   * @param loadFactor
   *
   * @throws IllegalArgumentException if capacity is not positive
   */
  protected CapacityLruLinkedHashMap(final int capacity,
                                     final int initialCapacity,
                                     final float loadFactor) {
    super(initialCapacity, loadFactor, true);

    if (capacity <= 0) {
      throw new IllegalArgumentException("capacity must be positive");
    }

    this.capacity = capacity;
  }

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

  /**
   * Returns capacity of map
   *
   * @return
   */
  public final int getCapacity() {
    return capacity;
  }

}