* called by the {@link #escape(String)} method when it discovers that escaping is required. It is
   * protected to allow subclasses to override the fastpath escaping function to inline their
   * escaping test. See {@link CharEscaperBuilder} for an example usage.
   *
   * @param s the literal string to be escaped
   * @param index the index to start escaping from
   * @return the escaped form of {@code string}

 * array contains information about special ASCII characters such as {@code \\t} and {@code \\n}
 * while {@link #escapeUnsafe} is overridden to handle general escaping of the form {@code \\uxxxx}.
 *
 * <p>The size of the data structure used by {@link ArrayBasedCharEscaper} is proportional to the
 * highest valued character that requires escaping. For example a replacement map containing the

   * called by the {@link #escape(String)} method when it discovers that escaping is required. It is
   * protected to allow subclasses to override the fastpath escaping function to inline their
   * escaping test. See {@link CharEscaperBuilder} for an example usage.
   *
   * <p>This method is not reentrant and may only be invoked by the top level {@link

@ElementTypesAreNonnullByDefault
public final class Escapers {
  private Escapers() {}

  /**
   * Returns an {@link Escaper} that does no escaping, passing all character data through unchanged.
   */
  public static Escaper nullEscaper() {
    return NULL_ESCAPER;
  }

  // An Escaper that efficiently performs no escaping.
  // Extending CharEscaper (instead of Escaper) makes Escapers.compose() easier.
  private static final Escaper NULL_ESCAPER =

 * general way.
 *
 * <p>A good example of usage of this class is for HTML escaping where the replacement array
 * contains information about the named HTML entities such as {@code &amp;} and {@code &quot;} while
 * {@link #escapeUnsafe} is overridden to handle general escaping of the form {@code &#NNNNN;}.
 *
 * <p>The size of the data structure used by {@link ArrayBasedUnicodeEscaper} is proportional to the

   * href="https://goo.gl/MplK6I">URL form parameter names and values</a>. Escaping is performed
   * with the UTF-8 character encoding. The caller is responsible for <a
   * href="https://goo.gl/9EfkM1">replacing any unpaired carriage return or line feed characters
   * with a CR+LF pair</a> on any non-file inputs before escaping them with this escaper.
   *
   * <p>When escaping a String, the following rules apply:
   *
   * <ul>

 * elements' text contents. When possible, avoid manual escaping by using templating systems and
 * high-level APIs that provide autoescaping. For example, consider <a
 * href="http://www.xom.nu/">XOM</a> or <a href="http://www.jdom.org/">JDOM</a>.
 *
 * <p><b>Note:</b> Currently the escapers provided by this class do not escape any characters
 * outside the ASCII character range. Unlike HTML escaping the XML escapers will not escape

 * most elements' text contents. When possible, avoid manual escaping by using templating
 * systems and high-level APIs that provide autoescaping.
 * One Google-authored templating system available for external use is <a
 * href="https://developers.google.com/closure/templates/">Closure Templates</a>.
 *
 * <p>HTML escaping is particularly tricky: For example, <a href="http://goo.gl/5TgZb">some

          '&', "<and>");
  private static final char[] NO_CHARS = new char[0];

  public void testReplacements() throws IOException {
    // In reality this is not a very sensible escaper to have (if you are only
    // escaping elements from a map you would use a ArrayBasedCharEscaper).
    UnicodeEscaper escaper =
        new ArrayBasedUnicodeEscaper(
            SIMPLE_REPLACEMENTS, Character.MIN_VALUE, Character.MAX_CODE_POINT, null) {

    // Escapers operate on characters: no characters, no escaping.
    Assert.assertEquals("", escaper.escape(""));
    // Assert that escapers throw null pointer exceptions.
    try {
      escaper.escape((String) null);
      Assert.fail("exception not thrown when escaping a null string");
    } catch (NullPointerException e) {
      // pass
    }
  }

  /**