java获取当前时间的前一个小时

public static void beforeOneHourToNowDate() {
    Calendar calendar = Calendar.getInstance();
    /* HOUR_OF_DAY 指示一天中小时 */
    calendar.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY) - 1);
    /* MINUTE 指示一天中的某分 */
    calendar.set(Calendar.MINUTE,(calendar.get(Calendar.MINUTE) - 20));
    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    System.out.println("一个小时前的时间：" + df.format(calendar.getTime()));
    System.out.println("当前的时间：" + df.format(new Date()));
  } 
public static void main(String[] args) {
    beforeOneHourToNowDateTime();
}

public static void main(String[] args) {
    Calendar calendar = Calendar.getInstance();
    /* HOUR_OF_DAY 指示一天中小时 */
    calendar.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY) - 1);
    /* MINUTE 指示一天中的某分 */
    calendar.set(Calendar.MINUTE,(calendar.get(Calendar.MINUTE) - 20));
    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    System.out.println("一个小时前的时间：" + df.format(calendar.getTime()));
    System.out.println("当前的时间：" + df.format(new Date()));
 }