java - 是否有必要在 java 函数中为时间创建两个日历实例？

Question

我正在开发一个应用程序，我必须找到每天上午 9 点和晚上 8 点的时间戳，并计算给定的时间戳是否在这些时间戳之间。 我的功能在下面给出，有人可以建议我是否有必要创建两个日历实例？需要帮助来优化这个功能

 boolean isDateTimeBetweenNineAMTOEightPM(long datetime) {
    long nineAM = 0, eightPM = 0;

    Calendar calendar = Calendar.getInstance();
    calendar.set(Calendar.HOUR, 9);
    calendar.set(Calendar.MINUTE, 00);
    calendar.set(Calendar.SECOND, 00);
    calendar.set(Calendar.AM_PM, Calendar.AM);
    nineAM = calendar.getTime().getTime() / 1000;

    calendar.set(Calendar.HOUR, 8);
    calendar.set(Calendar.MINUTE, 00);
    calendar.set(Calendar.SECOND, 00);
    calendar.set(Calendar.AM_PM, Calendar.PM);
    eightPM = calendar.getTime().getTime() / 1000;

    if (datetime >= nineAM && datetime <= eightPM) {
        return true;
    } else {
        return false;
    }
}

Answer 1

这样的事情怎么样？

boolean isDateTimeBetweenNineAMTOEightPM(
    long datetime) {
  final Calendar calendar = Calendar.getInstance(); // Get one calendar instance.
  calendar.set(Calendar.MINUTE, 0);                 // Set Minutes, Seconds, and Millis to 0.
  calendar.set(Calendar.SECOND, 0);
  calendar.set(Calendar.MILLISECOND, 0);

  calendar.set(Calendar.HOUR, 9);                   // 9 AM
  calendar.set(Calendar.AM_PM, Calendar.AM);
  final long nineAM = calendar.getTimeInMillis();   // In Millis.

  calendar.set(Calendar.HOUR, 8);                   // 8 PM
  calendar.set(Calendar.AM_PM, Calendar.PM);
  return (datetime >= nineAM && datetime <= calendar
      .getTimeInMillis());                         // Return.
}