Java-related class time

 

Prior knowledge (on time)

• Measurement Unit: ms
• A variable representing the number of milliseconds Type: lang
• Time: at 00:00 on July 1, 1970

Date class

• A date very primitive class, now basically abandoned, only briefly here

Common method

• new Date (): Returns the current time is a time of the object
• new Date (long time): Returns the object represents the time after the standard time is time milliseconds
• getTime (): returns the number of milliseconds from the standard time

Test implementation

1  // Create the current time of the object 
2 a Date DA1 = new new a Date ();
 . 3  // Create Time after time after the target 400,000,000 milliseconds 
. 4 a Date DA2 = new new a Date (400,000,000);

DateFormat class

• Abstract classes, subclasses need to implement SimpleDateFormate
• Formatting the output time for the object

SimpleDateFormat类

• DateFormat class inheritance to achieve

Format format

• yyyy-MM-dd hh: mm: ss in brackets
• Extraction of need, when the month or in several other dates, defined as only a few specific elements of the format on the line
• Special markers do not change, they have an ability to specify the variables can be identified
• Other such as "-", ":" You can change the date

Common method

• new SimpleDateFormat ( "yyyy-MM-dd hh: mm: ss") defines a format object formatted
• formate (target time) after the time of the object in terms of return string
• parse (specific string representing the date of the date format) represented by the character string recognition time format specified time into the object

Test implementation

1      // Create the current time of the object 
2      a Date DA1 = new new a Date ();
 . 3      // custom formatter formats 
. 4      DateFormat DF1 = new new the SimpleDateFormat ( "the MM-dd-YYYY HH: mm: SS" );        
 . 5      // formatted output 
. 6      String str1 = df1.format (DA1);
 . 7      System.out.println (str1); // 2020-01-09 02:43:38
 . 8      // another format 
. 9      DateFormat DF2 = new new the SimpleDateFormat ( "YYYY Year when mM month dd hh mm ss a day " );
 10      String str2 = df2.format (DA1);
 . 11     System.out.println (str2); // 2020 on January 2 when 09 minutes 38 seconds 43
 12      // formatted input 
13      a Date DA2 = df2.parse ( "2020 January 9 02 hours 00 minutes 38 seconds "); // here to throw an error 
14      a Date DA3 = df2.parse (" 2020 at 2:00:38 on January 9 " );
 15      System.out.println (DA2); // Thu 02 Jan 09 : 00: 38 is CST 2020 
16      System.out.println (DA3); // Thu Jan 09 02:00:38 CST 2020, so there is no 0 is the same, there may be some automatic conversion of
 17      // get a particular element 
18      DF3 = DateFormat new new SimpleDateFormat ( "yyyy Year" );
 19      String year = df3.format (DA1);
 20     System.out.println(year);//2020年

Canlendar class

• Abstract class, subclass of GregorianCalendar need to be implemented
• Examples of the addition time for the object, the relevant display and provide a calendar calculating function

GregorianCalendar class

• Class is a subclass of Canlendar implementation class
• Will print out a bunch of attributes of an object instance is directly output after the printing

Construction method

• 传参方式（year,month,day)、(year,month,day,hour,minute.........)
• Do not pass the reference date also represents the current object

Common method

• get (. Calendar element) to obtain a time element (such as YEAR, MONTH, Day OF WEEK, etc.) (Note: 0 corresponds to January 1 Sunday 2 Monday)
• set (Calendar. element values) the assignment of a time element
• add (Calendar. element value) positive values ​​indicate a new object represents the current time after many years (month, day), how many years (month, day) before the negative representation
• getTime () time is converted to an object of type Date
• setTime (Date da) Date Type Type Switch Calendar
• getActualMaximum (Calendar. elements) to obtain the maximum value of an element is currently located in the peripheral elements
• You can try to use a method of encapsulation format conversion implemented

Test implementation

1      // initialize the calendar object 
2      Calendar CAN1 = new new the GregorianCalendar (2020,3,5 );
 . 3      Calendar CAN2 = new new the GregorianCalendar (2020,3,5,5,6,3 );
 . 4      // get a specific element 
. 5      int year = can1.get (Calendar.YEAR);
 . 6      int day = can1.get (Calendar.DATE);
 . 7      System.out.println (year + "in" + day + "days" );
 8      // set a specific element 
. 9      can1.set (Calendar.YEAR, 1999 );
 10      int Yearn = can1.get (Calendar.YEAR);
 . 11     System.out.println(yearn+"年"+day+"天");
12     //加减运算
13     can1.add(Calendar.YEAR, 10);
14     System.out.println(can1.get(Calendar.YEAR)+"年");
15     can1.add(Calendar.YEAR, -10);
16     System.out.println(can1.get(Calendar.YEAR)+"年");
17     //与Date之间的转换
18     Date da=can1.getTime();
19     System.out.println(da);
20     can1.setTime(da);
21     System.out.println(can1.get(Calendar.YEAR)+"年"+can1.get(Calend
22     #######################
     
　　　2020 5 days
      in 1999, five days
      2009
      1999
      Mon Apr 05 00:00:00 CST 1999
      1999 5 days