起因：写代码的时候经常会用到获取当前时间戳和日期，现总结如下

public void testDate() {
       //SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");//设置日期格式     Date date = new Date();     String dateString = date.toString();     long times = date.getTime();     System.out.println("date.toString():"+date.toString());     System.out.println("当前时间戳（毫秒）：" + times);     Calendar c = Calendar.getInstance();     System.out.println("当前日期：" + c.get(Calendar.DATE));     System.out.println("当前年份:" + c.get(Calendar.YEAR));     //月份从0开始，0-11     System.out.println("当前月份:" + c.get(Calendar.MONTH));     //12小时制，0-11     System.out.println("12小时制：当前小时：" + c.get(Calendar.HOUR));     System.out.println("24小时制：当前小时：" + c.get(Calendar.HOUR_OF_DAY));     System.out.println("当前分钟：" + c.get(Calendar.MINUTE));     System.out.println("当前秒：" + c.get(Calendar.SECOND));     System.out.println("一年中的某天：" + c.get(Calendar.DAY_OF_YEAR));     System.out.println("当前时间戳(毫秒）：" + c.getTimeInMillis());     System.out.println("Calendar的toString()方法一般用作调试："+c.toString());     SimpleDateFormat df = new SimpleDateFormat("yyyyMMdd");     String currentDateStr = df.format(new Date());     System.out.println("当前日期yyyyMMdd:"+currentDateStr); }

　　

输出结果：

date.toString():Wed Aug 02 11:39:05 CST 2017

当前时间戳（毫秒）：1501645145298

当前日期：2

当前年份:2017

当前月份:7

12小时制：当前小时：11

24小时制：当前小时：11

当前分钟：39

当前秒：5

一年中的某天：214

当前时间戳(毫秒）：1501645145302

Calendar的toString()方法一般用作调试：java.util.GregorianCalendar[time=1501645145302,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=19,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2017,MONTH=7,WEEK_OF_YEAR=31,WEEK_OF_MONTH=1,DAY_OF_MONTH=2,DAY_OF_YEAR=214,DAY_OF_WEEK=4,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=11,HOUR_OF_DAY=11,MINUTE=39,SECOND=5,MILLISECOND=302,ZONE_OFFSET=28800000,DST_OFFSET=0]

当前日期yyyyMMdd:20170802