SimpleDateFormat in Java USES detail

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), (text - > date) and standardization.

SimpleDateFormat allows you to start in any user-specified manner 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 the default formatting. You can modify the formatting using the applyPattern method as needed.

Inheritance of SimpleDateFormat functions:

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

Here's a small example:

import java.text.*;
import java.util.Date;
/**
 SimpleDateFormat Function syntax: 
 G  Chronological marker 
 y  years 
 M  month 
 d  day 
 h  when   In the morning or afternoon  (1~12)
 H  when   in 1 In the day  (0~23)
 m  points 
 s  seconds 
 S  ms 
 E  week 
 D 1 Day of the year 
 F 1 What day of the month is it 
 w 1 Week of the year 
 W 1 Week of the month 
 a  In the morning  /  In the afternoon   markers  
 k  when   in 1 In the day  (1~24)
 K  when   In the morning or afternoon  (0~11)
 z  The time zone 
 */
public class FormatDateTime {
  public static void main(String[] args) {
    SimpleDateFormat myFmt=new SimpleDateFormat("yyyy years MM month dd day  HH when mm points ss seconds ");
    SimpleDateFormat myFmt1=new SimpleDateFormat("yy/MM/dd HH:mm"); 
    SimpleDateFormat myFmt2=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");// Is equivalent to now.toLocaleString()
    SimpleDateFormat myFmt3=new SimpleDateFormat("yyyy years MM month dd day  HH when mm points ss seconds  E ");
    SimpleDateFormat myFmt4=new SimpleDateFormat(
        "1 The first of the year  D  day  1 The first year w A few weeks  1 The first month W A few weeks   in 1 In the day k when  z The time zone ");
    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 minutes 27 seconds
04/12/16 17:24
2004-12-16 17:24:27
December 16, 2004 17:24:27 SEC Thursday
The 351st day of the year The third week of the 51st week of the year is 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

Here is JavaBean:

public class FormatDateTime {
  public static String toLongDateString(Date dt){
    SimpleDateFormat myFmt=new SimpleDateFormat("yyyy years MM month dd day  HH when mm points ss seconds  E ");    
    return myFmt.format(dt);
  }
  public static String toShortDateString(Date dt){
    SimpleDateFormat myFmt=new SimpleDateFormat("yy years MM month dd day  HH when mm points ");    
    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));
  }  
}

main test results called:

December 16, 2004 17:38:00 26 SEC Thursday
At 17:38 on December 16, 2004
17 38 26 0965
04/12/16 17:38