public void testToString() {
    assertToStringWorks(CharMatcher.anyOf(""), "CharMatcher.none()");
    assertToStringWorks(CharMatcher.anyOf("1"), "CharMatcher.is('\\u0031')");
    assertToStringWorks(CharMatcher.isNot('1'), "CharMatcher.isNot('\\u0031')");
    assertToStringWorks(CharMatcher.anyOf("12"), "CharMatcher.anyOf(\"\\u0031\\u0032\")");
    assertToStringWorks(CharMatcher.anyOf("321"), "CharMatcher.anyOf(\"\\u0031\\u0032\\u0033\")");

      return "CharMatcher.is('" + showCharacter(match) + "')";
    }
  }

  /** Implementation of {@link #isNot(char)}. */
  private static final class IsNot extends FastMatcher {

    private final char match;

    IsNot(char match) {
      this.match = match;
    }

    @Override
    public boolean matches(char c) {
      return c != match;
    }

    @Override

      return "CharMatcher.is('" + showCharacter(match) + "')";
    }
  }

  /** Implementation of {@link #isNot(char)}. */
  private static final class IsNot extends FastMatcher {

    private final char match;

    IsNot(char match) {
      this.match = match;
    }

    @Override
    public boolean matches(char c) {
      return c != match;
    }

    @Override