* with this ThreadFactory.
   *
   * <p><b>Java 21+ users:</b> use {@link Thread.Builder#name(String, long)} instead. Note that
   * {@link #setNameFormat} accepts a thread name <i>format string</i> (e.g., {@code
   * threadFactoryBuilder.setNameFormat("rpc-pool-%d")}), while {@code threadBuilder.name()} accepts
   * a thread name <i>prefix</i> and initial counter value (e.g., {@code
   * threadBuilder.name("rpc-pool-", 0)}.

    ThreadFactory factory = builder.setNameFormat(format).build();
    for (int i = 0; i < 11; i++) {
      assertThat(factory.newThread(monitoredRunnable).getName())
          .isEqualTo(rootLocaleFormat(format, i));
    }
  }

  public void testNameFormatWithPercentD_custom() {
    String format = "super-duper-thread-%d";
    ThreadFactory factory = builder.setNameFormat(format).build();
    for (int i = 0; i < 11; i++) {

    ThreadFactory factory = builder.setNameFormat(format).build();
    for (int i = 0; i < 11; i++) {
      assertThat(factory.newThread(monitoredRunnable).getName())
          .isEqualTo(rootLocaleFormat(format, i));
    }
  }

  public void testNameFormatWithPercentD_custom() {
    String format = "super-duper-thread-%d";
    ThreadFactory factory = builder.setNameFormat(format).build();
    for (int i = 0; i < 11; i++) {