3.Java Base Date Object

Bi Xiangdong Teacher Java Basic Learning Note--date Object

Today, after learning the date object in Java, I feel that this object is mainly useful to us in the following points.

1. Get the time and date and display it in your own defined format.

2. The time is displayed when the website is designed.

The knowledge points are as follows:

Java.util

the Date class represents a specific moment, accurate to milliseconds.

Prior to JDK 1.1, the class Date had two other functions. It allows you to interpret dates as year, month, day, hour, minute, and second values. It also allows formatting and parsing of date strings. However, the APIs for these functions are not easy to internationalize. Starting with JDK 1.1, you should use Calendar classes to convert between date and Time fields, using DateFormat classes to format and parse date strings. Dateis deprecated in the appropriate method.

Java.text

Class DateFormat

DateFormat is an abstract class of date/time formatting subclasses that formats and resolves dates or times in a language-independent manner. Date/time formatting subclasses (such as SimpleDateFormat) allow formatting (that is, date-and text), parsing (text-to-date), and normalization. Represents a date as an Date object, or as the number of milliseconds from GMT (Greenwich Mean Time) January 1, 1970 00:00:00 This moment.

public class SimpleDateFormat extends DateFormat

     SimpleDateFormatis a specific class that formats and resolves dates in a language-related way. It allows formatting (date-and text), parsing (text-to-date), and normalization. SimpleDateFormatallows you to select any user-defined pattern of date-time formats. However, it is still recommended DateFormat getTimeInstance getDateInstance getDateTimeInstance to create a date-time formatter by using the, or. Each of these class methods can return a date/time formatter initialized in the default format pattern. You can use methods as needed applyPattern to modify the format pattern.

Date and Time mode

Date and time formats are specified by a date and time pattern string. In a date and time pattern string, the unquoted letters ‘A‘ to ‘Z‘ and ‘a‘ to ‘z‘ are interpreted as pattern letters, which are used to represent date or time string elements. Text can be caused by using single quotation marks ( ‘ ) to avoid interpretation. "‘‘"represents a single quotation mark. All other characters are not interpreted; Simply copy them to the output string when they are formatted, or match the input string when parsing.

The following pattern letters are defined (all other characters ‘A‘ to ‘Z‘ and ‘a‘ to ‘z‘ are preserved):

Letters	date or time element	represents	Example
G	Era Marker	Text	AD
y	Years	Year	1996;96
M	Month of the Year	Month	July; Jul;07
w	Number of weeks in the year	Number	27
W	Number of weeks in the month	Number	2
D	Number of days in the year	Number	189
d	Number of days in month	Number	10
F	Week of the Month	Number	2
E	Days of the Week	Text	Tuesday;Tue
a	AM/PM Mark	Text	PM
H	Number of hours in the day (0-23)	Number	0
k	Number of hours in the day (1-24)	Number	24
K	Number of hours in am/pm (0-11)	Number	0
h	Number of hours in am/pm (1-12)	Number	12
m	Number of minutes in hours	Number	30
s	Number of seconds in minutes	Number	55
S	Number of milliseconds	Number	978
z	Time	General Time Zone	Pacific Standard Time; PST;GMT-08:00
Z	Time	RFC 822 Time Zone	-0800

Sample source code is as follows:

/**The ****************************** Date object is DateFormat in the Java.text package in the Java.util package ********************************/Importjava.text.*;ImportJava.util.*;classdatedemo{ Public Static voidMain (string[] args) {Date d=NewDate (); System.out.println (d);//printing time can not understand, want some format. //encapsulates a pattern into a SimpleDateFormat object. SimpleDateFormat sdf=NewSimpleDateFormat ("yyyy mm month DD Day"); //calls the format method to reformat the specified Date object. String Time=Sdf.format (d); System.out.println ("Time=" +Time ); }}

Program run:

3.Java Base Date Object