【java】Date与String之间的转换：java.text.SimpleDateFormat、public Date parse(String source) throws ParseException和public final String format(Date date)

 1 package 日期日历类;
 2 
 3 import java.text.ParseException;
 4 import java.text.SimpleDateFormat;
 5 import java.util.Date;
 6 
 7 public class TestDate {
 8     public static void main(String[] args) {
 9         Date date=new java.util.Date();
10         System.out.println(date);//Fri Apr 07 22:20:12 CST 2017
11         SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
12         String d=sdf.format(date);
13         System.out.println(d);//2017-04-07 22:20:12
14         String d2="2017-04-06 12:30:30";
15         Date date2=new Date();
16         try {
17             date2 = sdf.parse(d2);
18         } catch (ParseException e) {
19             e.printStackTrace();
20         }
21         System.out.println(date2);//Thu Apr 06 12:30:30 CST 2017
22     }
23 }

 1 package 日期日历类;
 2 
 3 import java.util.Calendar;
 4 import java.util.Date;
 5 
 6 public class TestDate {
 7     public static void main(String[] args) {
 8         Date date=new java.util.Date();
 9         System.out.println(date);//Fri Apr 07 22:53:21 CST 2017
10         Calendar cal=Calendar.getInstance();
11         System.out.println(cal);//java.util.GregorianCalendar[time=1491576801409,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=3,WEEK_OF_YEAR=14,WEEK_OF_MONTH=2,DAY_OF_MONTH=7,DAY_OF_YEAR=97,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=1,AM_PM=1,HOUR=10,HOUR_OF_DAY=22,MINUTE=53,SECOND=21,MILLISECOND=409,ZONE_OFFSET=28800000,DST_OFFSET=0]
12         Date date2=cal.getTime();//Calendar转为Date
13         System.out.println(date2);//Fri Apr 07 22:53:21 CST 2017
14         StringBuffer sb=new StringBuffer();
15         
16         //月份从0开始算，所以要加1
17         sb.append(cal.get(Calendar.YEAR)).append("年").append(cal.get(Calendar.MONTH)+1).append("月").append(cal.get(Calendar.DAY_OF_MONTH)).append("日").append(cal.get(Calendar.HOUR_OF_DAY)).append(":").append(cal.get(Calendar.MINUTE)).append(":").append(cal.get(Calendar.SECOND));
18         System.out.println(sb);//2017年4月7日22:53:21
19     }
20 }