}

  public void testRetainFrom() {
    assertEquals("aaa", is('a').retainFrom("bazaar"));
    assertEquals("z", is('z').retainFrom("bazaar"));
    assertEquals("!", is('!').retainFrom("!@#$%^&*()-="));
    assertEquals("", is('x').retainFrom("bazaar"));
    assertEquals("", is('a').retainFrom(""));
  }

  public void testPrecomputedOptimizations() {

  }

  public void testRetainFrom() {
    assertEquals("aaa", is('a').retainFrom("bazaar"));
    assertEquals("z", is('z').retainFrom("bazaar"));
    assertEquals("!", is('!').retainFrom("!@#$%^&*()-="));
    assertEquals("", is('x').retainFrom("bazaar"));
    assertEquals("", is('a').retainFrom(""));
  }

  public void testPrecomputedOptimizations() {

    return count;
  }

  /**
   * Returns a string containing all non-matching characters of a character sequence, in order. For
   * example:
   *
   * {@snippet :
   * CharMatcher.is('a').removeFrom("bazaar")
   * }
   *
   * ... returns {@code "bzr"}.
   */
  public String removeFrom(CharSequence sequence) {
    String string = sequence.toString();
    int pos = indexIn(string);
    if (pos == -1) {