java开始到熟悉66-69

本次内容：DateFormat类

1、DateFormat类

 1 package array;

 2 /**

 3  * 时间和字符串之间的转化

 4  */

 5 import java.text.DateFormat;

 6 import java.text.ParseException;

 7 import java.text.SimpleDateFormat;

 8 import java.util.Date;

 9

10 public class dateformat {

11     public static void main(String[] args) throws ParseException

12     {

13         DateFormat d=new SimpleDateFormat("yyyy-MM-dd");

14         Date t=new Date(123);

15         String str=d.format(t);//将时间对象按照格式化字符串，转换成字符串

16         System.out.println(str);

17         System.out.println("###################");

18         String str1="1977,7,7";

19         DateFormat d1=new SimpleDateFormat("yyyy,MM,dd");//此处字符串格式必须和前面的字符串格式一致，或前面的字符串按此格式定义

20         Date t1=d1.parse(str1);//将相应格式的字符串转换成时间

21         System.out.println(t1);

22     }

23 }

运行结果：
1970-01-01
###################
Thu Jul 07 00:00:00 CST
1977

2、Calendar类

 1 package array;

 2 /**

 3  * 此时日历类及日期计算

 4  */

 5 import java.util.Calendar;

 6 import java.util.Date;

 7 import java.util.GregorianCalendar;

 8

 9 public class gregorian {

10     public static void main(String[] args)

11     {

12         Calendar c=new GregorianCalendar();

13         c.set(2001,1,1,12,12,12);

14         Date d=c.getTime();

15         System.out.println(d);

16         System.out.println(c.getTime());

17         System.out.println("###################");

18         Calendar c1=new GregorianCalendar();

19         c1.set(Calendar.YEAR, 2014);

20         c1.set(Calendar.MONTH,5);

21         c1.set(Calendar.DAY_OF_MONTH,1);

22         System.out.println(c1.getTime());

23         System.out.println(c1.get(Calendar.MONTH));

24         System.out.println("###################");

25         c1.add(Calendar.MONTH,1);//月份加1

26         System.out.println(c1.get(Calendar.MONTH));

27         c1.add(Calendar.MONTH,-1);//月份减1

28         System.out.println(c1.get(Calendar.MONTH));

29     }

30 }

运行结果：
Thu Feb 01 12:12:12 CST 2001
Thu Feb 01 12:12:12 CST
2001
###################
Sun Jun 01 10:56:52 CST
2014
5
###################
6
5

3、一个可视化日历练习：

 1 package array;

 2

 3 import java.text.DateFormat;

 4 import java.text.ParseException;

 5 import java.text.SimpleDateFormat;

 6 import java.util.Calendar;

 7 import java.util.Date;

 8 import java.util.GregorianCalendar;

 9 import java.util.Scanner;

10

11

12 public class visualcalendar {

13     public static void main(String[] args) throws ParseException

14     {

15         System.out.println("请输入日期（格式为某年-某月-某日）：");

16         Scanner input=new Scanner(System.in);

17         String str=input.nextLine();

18         DateFormat df=new SimpleDateFormat("yyyy-MM-dd");

19         Date d=df.parse(str);

20         Calendar c=new GregorianCalendar();

21         c.setTime(d);

22         int currentday=c.get(Calendar.DATE);

23         c.set(Calendar.DATE, 1);

24         System.out.println(c.get(Calendar.DAY_OF_WEEK));

25         System.out.println(c.getActualMaximum(Calendar.DATE));

26         System.out.println("日\t一\t二\t三\t四\t五\t六");

27         int day=c.get(Calendar.DAY_OF_WEEK);

28         int max=c.getActualMaximum(Calendar.DATE);

29         int i,j;

30         for(j=0;j<(day-1);j++)

31         {

32             System.out.print("\t");

33         }

34         for(i=1;i<=max;i++)

35         {

36             System.out.print(i);

37             if(i==currentday)

38             {

39                 System.out.print("*");

40             }

41             System.out.print(‘\t‘);

42             int grade=c.get(Calendar.DAY_OF_WEEK);

43             if(grade==Calendar.SATURDAY)

44                 System.out.println();

45             c.add(Calendar.DATE, 1);

46         }

47     }

48 }

运行结果：

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