*
   * <ul>
   *   <li>{@link #JAVA_EXT_DIRS} was deprecated in Java 8 and removed in Java 9. We have not
   *       confirmed whether it is available under older versions.
   *   <li>{@link #JAVA_COMPILER}, while still listed as required as of Java 15, is typically not
   *       available even under older version.
   *   <li>Any property may be cleared through APIs like {@link System#clearProperty}.

     * <p><b>Algorithm:</b>
     * If the given path is a directory, then there is a choice:
     * </p>
     * <ul>
     *   <li><b>Package hierarchy:</b> if a {@code module-info.class} file is found at the root,
     *       then builds a singleton map with the module name declared in that descriptor.</li>
     *   <li><b>Module hierarchy:</b> if {@code module-info.class} files are found in sub-directories,

    /**
     * クラスローダを返します。
     * <p>
     * クラスローダは以下の順で検索します。
     * </p>
     * <ol>
     * <li>呼び出されたスレッドにコンテキスト・クラスローダが設定されている場合はそのコンテキスト・クラスローダ</li>
     * <li>ターゲット・クラスをロードしたクラスローダを取得できればそのクラスローダ</li>
     * <li>このクラスをロードしたクラスローダを取得できればそのクラスローダ</li>
     * <li>システムクラスローダを取得できればそのクラスローダ</li>
     * </ol>
     * <p>
     * ただし、ターゲット・クラスをロードしたクラスローダとこのクラスをロードしたクラスローダの両方が取得できた場合で、

     * <ul>
     *   <li>If it starts with either "pom." or "project.", the expression is evaluated against the model.</li>
     *   <li>If the value is null, get the value from the context.</li>
     *   <li>If the value is null, but the context contains the expression, don't replace the expression string
     *       with the value, and continue to find other expressions.</li>

 *
 * <p>For instance, if <i>steps</i> is 5, one example sequence that will be tested is:
 *
 * <ol>
 *   <li>remove();
 *   <li>hasNext()
 *   <li>hasNext();
 *   <li>remove();
 *   <li>next();
 * </ol>
 *
 * <p>This particular order of operations may be unrealistic, and testing all 3^5 of them may be

 *
 * <p>Cache statistics are incremented according to the following rules:
 *
 * <ul>
 *   <li>When a cache lookup encounters an existing cache entry {@code hitCount} is incremented.
 *   <li>When a cache lookup first encounters a missing cache entry, a new entry is loaded.
 *       <ul>
 *         <li>After successfully loading an entry {@code missCount} and {@code loadSuccessCount}

  }

  /**
   * Verifies that a collection is immutable.
   *
   * <p>A collection is considered immutable if:
   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>

 *
 * <p>Cache statistics are incremented according to the following rules:
 *
 * <ul>
 *   <li>When a cache lookup encounters an existing cache entry {@code hitCount} is incremented.
 *   <li>When a cache lookup first encounters a missing cache entry, a new entry is loaded.
 *       <ul>
 *         <li>After successfully loading an entry {@code missCount} and {@code loadSuccessCount}

 * http://download.oracle.com/javase/1.5.0/docs/tooldocs/solaris/javadoc.html#documentationcomments for details.
 *
 * <ul>
 * <li>Removes leading '*' characters.</li>
 * <li>Removes block tags.</li>
 * <li>Removes leading and trailing empty lines.</li>
 * </ul>
 */
class JavadocScanner {
    private final StringBuilder input = new StringBuilder();
    private int pos;
    private int markPos;

     * <ul>
     * <li>collect all the vertices for the projects that we want to build.</li>
     * <li>iterate through the deps of each project and if that dep is within
     * the set of projects we want to build then add an edge, otherwise throw
     * the edge away because that dependency is not within the set of projects
     * we are trying to build. we assume a closed set.</li>
     * <li>do a topo sort on the graph that remains.</li>