Years.java

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 *
 * Copyright (c) 2006-2010 by Public Library of Science
 * http://plos.org
 * http://ambraproject.org
 *
 * 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
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package org.ambraproject.views.article;

import java.util.TreeMap;

/**
 * An ordered list of years (as year numbers). Each year has a list of months.
 */
public class Years extends TreeMap<Integer, Months> {
  /**
   * @return the list of months (possibly emtpy, but always non-null)
   */
  public Months getMonths(Integer year) {
    Months months = get(year);
    if (months == null)
      put(year, months = new Months());
    return months;
  }
}