Detailed explanation of the sample code used by SimpleDateFormat in Java

SimpleDateFormat is a concrete class for formatting and analyzing data in a country-sensitive manner. This article mainly introduces the detailed use of SimpleDateFormat in Java. Friends in need can refer to

public class SimpleDateFormat extends DateFormat

SimpleDateFormat is a specific class that formats and analyzes data in a country-sensitive manner. It allows formatting (date -> text), parsing (text -> date) and normalization.

SimpleDateFormat allows the selection of any user-specified method for date-time formatting. However, you want to create a date-time formatter using getTimeInstance, getDateInstance, or getDateTimeInstance from DateFormat. Each class method returns a date/time formatter initialized with default formatting. You can use the applyPattern method to modify the formatting method as needed.

SimpleDateFormatInheritance of functionRelationship:

Java.lang.Object
  |
  +----java.text.Format
      |
      +----java.text.DateFormat
          |
          +----java.text.SimpleDateFormat

The following is a small example:

import java.text.*;
import java.util.Date;
/**
 SimpleDateFormat函数语法：
 G 年代标志符
 y 年
 M 月
 d 日
 h 时 在上午或下午 (1~12)
 H 时 在一天中 (0~23)
 m 分
 s 秒
 S 毫秒
 E 星期
 D 一年中的第几天
 F 一月中第几个星期几
 w 一年中第几个星期
 W 一月中第几个星期
 a 上午 / 下午 标记符 
 k 时 在一天中 (1~24)
 K 时 在上午或下午 (0~11)
 z 时区
 */
public class FormatDateTime {
  public static void main(String[] args) {
    SimpleDateFormat myFmt=new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒");
    SimpleDateFormat myFmt1=new SimpleDateFormat("yy/MM/dd HH:mm"); 
    SimpleDateFormat myFmt2=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//等价于now.toLocaleString()
    SimpleDateFormat myFmt3=new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒 E ");
    SimpleDateFormat myFmt4=new SimpleDateFormat(
        "一年中的第 D 天 一年中第w个星期 一月中第W个星期 在一天中k时 z时区");
    Date now=new Date();
    System.out.println(myFmt.format(now));
    System.out.println(myFmt1.format(now));
    System.out.println(myFmt2.format(now));
    System.out.println(myFmt3.format(now));
    System.out.println(myFmt4.format(now));
    System.out.println(now.toGMTString());
    System.out.println(now.toLocaleString());
    System.out.println(now.toString());
  }  
}

Effect:

December 16, 2004 17:24:27
04/12/16 17:24
2004-12-16 17:24:27
December 16, 2004 17:24 27 seconds Thursday
The 351st day of the year The 51st Monday of the year The 3rd week of the month At 17:00 CST time zone of the day

16 Dec 2004 09:24:27 GMT
2004-12-16 17:24:27
Thu Dec 16 17:24:27 CST 2004

The following is a JavaBean:

public class FormatDateTime {
  public static String toLongDateString(Date dt){
    SimpleDateFormat myFmt=new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒 E ");    
    return myFmt.format(dt);
  }
  public static String toShortDateString(Date dt){
    SimpleDateFormat myFmt=new SimpleDateFormat("yy年MM月dd日 HH时mm分");    
    return myFmt.format(dt);
  }  
  public static String toLongTimeString(Date dt){
    SimpleDateFormat myFmt=new SimpleDateFormat("HH mm ss SSSS");    
    return myFmt.format(dt);
  }
  public static String toShortTimeString(Date dt){
    SimpleDateFormat myFmt=new SimpleDateFormat("yy/MM/dd HH:mm");    
    return myFmt.format(dt);
  }
  public static void main(String[] args) {
    Date now=new Date();
    System.out.println(FormatDateTime.toLongDateString(now));
    System.out.println(FormatDateTime.toShortDateString(now));
    System.out.println(FormatDateTime.toLongTimeString(now));
    System.out.println(FormatDateTime.toShortTimeString(now));
  }  
}

The main test result called:

Thursday, December 16, 2004 17:38:26
December 16, 2004 17:38
17 38 26 0965
04/12/16 17:38

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