Matcher matcher = linkPattern.matcher(line);
        while (matcher.find()) {
            MatchResult xrefMatcher = matcher.toMatchResult();
            String link = xrefMatcher.group(1);
            if (link.contains("#")) {
                Matcher linkMatcher = linkWithHashPattern.matcher(link);
                if (linkMatcher.matches()) {

        return new ConcurrentSkipListMap<>();
    }

    /**
     * {@link ConcurrentSkipListMap}の新しいインスタンスを作成して返します。
     *
     * @param <K>
     *            {@link ConcurrentSkipListMap}のキーの型
     * @param <V>
     *            {@link ConcurrentSkipListMap}の値の型
     * @param c
     *            {@link Comparator}
     * @return {@link ConcurrentSkipListMap}の新しいインスタンス

    /** {@link #line}が空であることを示す{@literal String}オブジェクト */
    protected static final String EMPTY = new String();

    /** {@link BufferedReader} */
    protected final BufferedReader reader;

    /** 読み込み済みの文字列 */
    protected String line = EMPTY;

    /**
     * for each構文で使用するために{@link LineIterator}をラップした{@link Iterable}を返します。
     *
     * @param reader

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   * #add}, you may wish to override {@link #addAll} to forward to this implementation.
   *
   * @since 7.0
   */
  protected boolean standardAddAll(Collection<? extends E> collection) {
    return Iterators.addAll(this, collection.iterator());
  }

  /**
   * A sensible definition of {@link #remove} in terms of {@link #iterator}, using the iterator's

   * you override {@link #listIterator()}, you may wish to override {@link #iterator} to forward to
   * this implementation.
   *
   * @since 7.0
   */
  protected Iterator<E> standardIterator() {
    return listIterator();
  }

  /**
   * A sensible default implementation of {@link #listIterator()}, in terms of {@link

  public E lower(@ParametricNullness E e) {
    return delegate().lower(e);
  }

  /**
   * A sensible definition of {@link #lower} in terms of the {@code descendingIterator} method of
   * {@link #headSet(Object, boolean)}. If you override {@link #headSet(Object, boolean)}, you may
   * wish to override {@link #lower} to forward to this implementation.
   */
  @CheckForNull
  protected E standardLower(@ParametricNullness E e) {

  }

  /**
   * A sensible implementation of {@link SortedMultiset#elementSet} in terms of the following
   * methods: {@link SortedMultiset#clear}, {@link SortedMultiset#comparator}, {@link
   * SortedMultiset#contains}, {@link SortedMultiset#containsAll}, {@link SortedMultiset#count},
   * {@link SortedMultiset#firstEntry} {@link SortedMultiset#headMultiset}, {@link

    return new RegularLinearTransformation(slope, y);
  }

  /**
   * Builds an instance for datasets which contains {@link Double#NaN}. The {@link #isHorizontal}
   * and {@link #isVertical} methods return {@code false} and the {@link #slope}, and {@link
   * #transform} methods all return {@link Double#NaN}. The {@link #inverse} method returns the same
   * instance.
   */
  public static LinearTransformation forNaN() {

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