Java date conversion simpledateformat format Daquan and judge whether it is a legal Date and Time string?

24-hour time display:

public class Datetime {     public static void main(String args[]){          java.util.Date current=new java.util.Date();            java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");            String c=sdf.format(current);            System.out.println(c);     } }

12-hour time display:

public class Datetime {     public static void main(String args[]){          java.util.Date current=new java.util.Date();            java.text.SimpleDateFormat sdf=new java.text.SimpleDateFormat("yyyy-MM-dd hh:mm:ss");            String c=sdf.format(current);            System.out.println(c);     } }

Difference: yyyy-mm-dd hh: mm: SS; yyyy-mm-dd hh: mm: SS

As follows:

Letter	Date or time element	Indicates	Example
G	Era identifier	Text	AD
y	Year	Year	1996;96
M	Month in Year	Month	July;Jul;07
w	Week in Year	Number	27
W	The number of weeks in the month	Number	2
D	Days in years	Number	189
d	Days in a month	Number	10
F	Week in the month	Number	2
E	Days in a week	Text	Tuesday;Tue
a	AM/PM mark	Text	PM
H	Hours in a day (0-23)	Number	0
k	Hours per day (1-24)	Number	24
K	Hours in AM/PM (0-11)	Number	0
h	Hours in AM/PM (1-12)	Number	12
m	Minutes in an hour	Number	30
s	Seconds in minutes	Number	55
S	Milliseconds	Number	978
z	Time Zone	General Time Zone	Pacific Standard Time;PST;GMT-08:00
Z	Time Zone	RFC 822 Time Zone	-0800

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Public class judgedate {

/**
* Judge whether it is a valid date and time string
* @ Param str_input
* @ Return Boolean; true: false.
*/
Public static Boolean isdate (string str_input, string rdateformat ){
If (! Isnull (str_input )){
Simpledateformat formatter = new simpledateformat (rdateformat );
Formatter. setlenient (false );
Try {
Formatter. Format (formatter. parse (str_input ));
} Catch (exception e ){
Return false;
}
Return true;
}
Return false;

}
Public static Boolean isnull (string Str ){
If (STR = NULL)
Return true;
Else
Return false;
}
Public static void main (string ARGs []) {
String STR = "2007-5-12 ";
If (isdate (STR, "YYYY. Mm. dd") | isdate (STR, "yyyy-mm-dd "))
System. Out. Print ("this is true ");
Else
System. Out. println (STR );
}
}