public String toString(Locale locale) {
    Format format = Format.forLocale(locale);
    Optional<String> deltaCpu = cpu.map(format::duration);
    String avgCpus = cpu.map(cpuTime -> " avg:" + format.decimal(cpuTime.toNanos() * 1d / wall.toNanos()))
      .orElse("");
    String gcString = gc.compareTo(Duration.ofSeconds(1)) > 0 ? (" gc:" + format.duration(gc)) : "";
    return format.duration(wall) + " cpu:" + deltaCpu.orElse("-") + gcString + avgCpus;
  }
Returns the amount of time elapsed between {@code other} and {@code this}.
planetiler-core/src/main/java/com/onthegomap/planetiler/stats/ProcessTime.java