本篇内容介绍了“用Calendar、Date和SimperFormat获取当前时间的区别”的有关知识,在实际案例的操作过程中,不少人都会遇到这样的困境,接下来就让小编带领大家学习一下如何处理这些情况吧!希望大家仔细阅读,能够学有所成!
Calendar calendar = Calendar.getInstance(); System.out.println("目前时间: " + calendar.getTime()); System.out.println("Calendar时区: " + calendar.getTimeZone().getID()); System.out.println("user.timezone: " + System.getProperty("user.timezone")); System.out.println("user.country: " + System.getProperty("user.country")); System.out.println("默认时区: " + TimeZone.getDefault().getID());
运行结果:
目前时间: Tue May 28 23:09:31 CST 2019
Calendar时区: Asia/Shanghai
user.timezone: Asia/Shanghai
user.country: CN
默认时区: Asia/Shanghai
long start1 = System.currentTimeMillis(); SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//设置日期格式 System.out.println(sdf.format(new Date()));// new Date()为获取当前系统时间 long end1 = System.currentTimeMillis(); System.out.println((end1 - start1) + "ms");
运行结果:
2019-05-28 23:14:14
55ms
long start2 = System.currentTimeMillis(); Calendar calendar = Calendar.getInstance();//可以对每个时间域单独修改 System.out.println(calendar.get(Calendar.YEAR) + "-" + calendar.get(Calendar.MONTH) + "-" + calendar.get(Calendar.DATE) + " " + calendar.get(Calendar.HOUR_OF_DAY) + ":" + calendar.get(Calendar.MINUTE) + ":" + calendar.get(Calendar.SECOND)); long end2 = System.currentTimeMillis(); System.out.println((end2 - start2) + "ms");
运行结果:
2019-4-28 23:15:22
36ms
显然,第二种的Calendar获取当前时间的性能比SimpleDateFormat的要快
long start3 = System.currentTimeMillis(); Calendar calendar = Calendar.getInstance(); calendar.setTime(new Date()); calendar.set(Calendar.HOUR_OF_DAY, 0); calendar.set(Calendar.MINUTE, 0); calendar.set(Calendar.SECOND, 0); Date zero = calendar.getTime(); long end3 = System.currentTimeMillis(); System.out.println(zero); System.out.println((end3 - start3) + "ms");
运行结果:
Tue May 28 00:00:00 CST 2019
34ms
long start4 = System.currentTimeMillis(); long current = System.currentTimeMillis(); long zero = current/(1000*3600*24)*(1000*3600*24) - TimeZone.getDefault().getRawOffset(); System.out.println(zero); long end4 = System.currentTimeMillis(); System.out.println((end4 - start4) + "ms");
运行结果:
1558972800000
11ms
这里current表示毫秒,那么除以了1000 * 3600 * 24得到天数,但是可能不是整数天,但是因为t是long型,那么小数部分没有了,再去乘以1000 * 3600 * 24,就变成整数天数所对应的毫秒了。
TimeZone.getDefault().getRawOffset() 计算夏令时和返回当前时区与格林尼治时间的偏差。
显然,这里获取零点时间强烈推荐第二种方法,性能比第一种高三倍左右。
import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; public class TestDate { /** * 获取当前年份、月份、日期 * @param args */ public static void main(String[] args) { Calendar cale = null; cale = Calendar.getInstance(); int year = cale.get(Calendar.YEAR); int month = cale.get(Calendar.MONTH) + 1; int day = cale.get(Calendar.DATE); int hour = cale.get(Calendar.HOUR_OF_DAY); int minute = cale.get(Calendar.MINUTE); int second = cale.get(Calendar.SECOND); int dow = cale.get(Calendar.DAY_OF_WEEK); int dom = cale.get(Calendar.DAY_OF_MONTH); int doy = cale.get(Calendar.DAY_OF_YEAR); System.out.println("Current Date: " + cale.getTime()); System.out.println("Year: " + year); System.out.println("Month: " + month); System.out.println("Day: " + day); System.out.println("Hour: " + hour); System.out.println("Minute: " + minute); System.out.println("Second: " + second); System.out.println("Day of Week: " + dow); System.out.println("Day of Month: " + dom); System.out.println("Day of Year: " + doy); // 获取当月第一天和最后一天 SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd"); String firstday, lastday; // 获取前月的第一天 cale = Calendar.getInstance(); cale.add(Calendar.MONTH, 0); cale.set(Calendar.DAY_OF_MONTH, 1); firstday = format.format(cale.getTime()); // 获取前月的最后一天 cale = Calendar.getInstance(); cale.add(Calendar.MONTH, 1); cale.set(Calendar.DAY_OF_MONTH, 0); lastday = format.format(cale.getTime()); System.out.println("本月第一天和最后一天分别是 : " + firstday + " and " + lastday); // 获取当前日期字符串 Date d = new Date(); System.out.println("当前日期字符串1:" + format.format(d)); System.out.println("当前日期字符串2:" + year + "/" + month + "/" + day + " " + hour + ":" + minute + ":" + second); } }
“用Calendar、Date和SimperFormat获取当前时间的区别”的内容就介绍到这里了,感谢大家的阅读。如果想了解更多行业相关的知识可以关注亿速云网站,小编将为大家输出更多高质量的实用文章!
免责声明:本站发布的内容(图片、视频和文字)以原创、转载和分享为主,文章观点不代表本网站立场,如果涉及侵权请联系站长邮箱:is@yisu.com进行举报,并提供相关证据,一经查实,将立刻删除涉嫌侵权内容。