工作笔记,记录下Calendar使用中容易忽略的问题,测试代码如下:
public class Test {
public static void main(String[] args){
//比较Calendar.HOUR_OF_DAY和Calendar.HOUR区别
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Calendar firstCal = Calendar.getInstance();
firstCal.set(Calendar.HOUR_OF_DAY, 0);
firstCal.set(Calendar.MINUTE, 0);
firstCal.set(Calendar.SECOND, 0);
firstCal.set(Calendar.MILLISECOND, 0);
String firstStr = dateFormat.format(firstCal.getTime());
System.out.println("通过HOUR_OF_DAY设置小时" + firstStr);
Calendar secondCal = Calendar.getInstance();
secondCal.set(Calendar.HOUR, 0);
secondCal.set(Calendar.MINUTE, 0);
secondCal.set(Calendar.SECOND, 0);
secondCal.set(Calendar.MILLISECOND, 0);
String secondStr = dateFormat.format(secondCal.getTime());
System.out.println("通过HOUR设置小时" + secondStr);
//比较不设置毫秒数和设置毫秒数的差异
Calendar threeCal = Calendar.getInstance();
threeCal.set(Calendar.HOUR, 0);
threeCal.set(Calendar.MINUTE, 0);
threeCal.set(Calendar.SECOND, 0);
System.out.println("设置毫秒数为0的总毫秒数" + secondCal.getTimeInMillis() + "毫秒值为" + secondCal.get(Calendar.MILLISECOND));
System.out.println("没设毫秒数为0的总毫秒数" + threeCal.getTimeInMillis() + "毫秒值为" + threeCal.get(Calendar.MILLISECOND));
}
}
总结:
1.设置小时时,使用HOUR_OF_DAY,24小时制,HOUR表示的是12小时制
2.尽量设置Calendar.MILLISECOND,防止Calendar(yyyy-MM-dd)和date(yyyy-MM-dd)比较时,因为毫秒不一致,导致normDateConpareResult不为0
int normDateCompareResult = healthUserNormStatistics.getNormDate().compareTo(today.getTime());