java时间类 date 和calendar类使用 Java时间类Date类和Calendar类的使用详解

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);
}
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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