java开始到熟悉66-69

本次内容：DateFormat类

1、DateFormat类

 package array;
 /**
  * 时间和字符串之间的转化
  */
 import java.text.DateFormat;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Date;
 
 public class dateformat {
     public static void main(String[] args) throws ParseException
     {
         DateFormat d=new SimpleDateFormat("yyyy-MM-dd");
         Date t=new Date(123);
         String str=d.format(t);//将时间对象按照格式化字符串，转换成字符串
         System.out.println(str);
         System.out.println("###################");
         String str1="1977,7,7";
         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
         Date t1=d1.parse(str1);//将相应格式的字符串转换成时间
         System.out.println(t1);
     }
 }

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

2、Calendar类

 package array;
 /**
  * 此时日历类及日期计算
  */
 import java.util.Calendar;
 import java.util.Date;
 import java.util.GregorianCalendar;
 
 public class gregorian {
     public static void main(String[] args)
     {
         Calendar c=new GregorianCalendar();
         c.set(2001,1,1,12,12,12);
         Date d=c.getTime();
         System.out.println(d);
         System.out.println(c.getTime());
         System.out.println("###################");
         Calendar c1=new GregorianCalendar();
         c1.set(Calendar.YEAR, 2014);
         c1.set(Calendar.MONTH,5);
         c1.set(Calendar.DAY_OF_MONTH,1);
         System.out.println(c1.getTime());
         System.out.println(c1.get(Calendar.MONTH));
         System.out.println("###################");
         c1.add(Calendar.MONTH,1);//月份加1
         System.out.println(c1.get(Calendar.MONTH));
         c1.add(Calendar.MONTH,-1);//月份减1
         System.out.println(c1.get(Calendar.MONTH));
     }
 }

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：

 package array;
 
 import java.text.DateFormat;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Date;
 import java.util.GregorianCalendar;
 import java.util.Scanner;
 
 public class visualcalendar {
     public static void main(String[] args) throws ParseException
     {
         System.out.println("请输入日期（格式为某年-某月-某日）：");
         Scanner input=new Scanner(System.in);
         String str=input.nextLine();
         DateFormat df=new SimpleDateFormat("yyyy-MM-dd");
         Date d=df.parse(str);
         Calendar c=new GregorianCalendar();
         c.setTime(d);
         int currentday=c.get(Calendar.DATE);
         c.set(Calendar.DATE, 1);
         System.out.println(c.get(Calendar.DAY_OF_WEEK));
         System.out.println(c.getActualMaximum(Calendar.DATE));
         System.out.println("日\t一\t二\t三\t四\t五\t六");
         int day=c.get(Calendar.DAY_OF_WEEK);
         int max=c.getActualMaximum(Calendar.DATE);
         int i,j;
         for(j=0;j<(day-1);j++)
         {
             System.out.print("\t");
         }
         for(i=1;i<=max;i++)
         {
             System.out.print(i);
             if(i==currentday)
             {
                 System.out.print("*");
             }
             System.out.print('\t');
             int grade=c.get(Calendar.DAY_OF_WEEK);
             if(grade==Calendar.SATURDAY)
                 System.out.println();
             c.add(Calendar.DATE, 1);
         }
     }
 }

运行结果：