将日期时间转换为24小时格式

You should take a look at Java date formatting, in particular SimpleDateFormat. There's some examples here: http://download.oracle.com/javase/tutorial/i18n/format/simpleDateFormat.html - but you can also find a lot more with a quick google.

Try this:

String dateStr = "Jul 27, 2011 8:35:29 AM";
DateFormat readFormat = new SimpleDateFormat( "MMM dd, yyyy hh:mm:ss aa");
DateFormat writeFormat = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss");
Date date = null;
try {
date = readFormat.parse(dateStr);
} catch (ParseException e) {
e.printStackTrace();
}


if (date != null) {
String formattedDate = writeFormat.format(date);
}

Try this:

Date date=new Date("12/12/11 8:22:09 PM");
System.out.println("Time in 24Hours ="+new SimpleDateFormat("HH:mm").format(date));

just a tip,

try to use JodaTime instead of java,util.Date it is much more powerfull and it has a method toString("") that you can pass the format you want like toString("yyy-MM-dd HH:mm:ss");

http://joda-time.sourceforge.net/

H vs h is difference between 24 hour vs 12 hour format.

I am taking an example of date given below and print two different format of dates according to your requirements.

String date="01/10/2014 05:54:00 PM";


SimpleDateFormat simpleDateFormat=new SimpleDateFormat("dd/MM/yyyy hh:mm:ss aa",Locale.getDefault());


try {
Log.i("",""+new SimpleDateFormat("ddMMyyyyHHmmss",Locale.getDefault()).format(simpleDateFormat.parse(date)));


Log.i("",""+new SimpleDateFormat("dd/MM/yyyy HH:mm:ss",Locale.getDefault()).format(simpleDateFormat.parse(date)));


} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

If you still have any query, Please respond. Thanks.

import java.text.SimpleDateFormat;


import java.util.Date;


public class DateFormatExample {


public static void main(String args[]) {


// This is how to get today's date in Java
Date today = new Date();


//If you print Date, you will get un formatted output
System.out.println("Today is : " + today);


//formatting date in Java using SimpleDateFormat
SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("dd-MM-yyyy");
String date = DATE_FORMAT.format(today);
System.out.println("Today in dd-MM-yyyy format : " + date);


//Another Example of formatting Date in Java using SimpleDateFormat
DATE_FORMAT = new SimpleDateFormat("dd/MM/yy");
date = DATE_FORMAT.format(today);
System.out.println("Today in dd/MM/yy pattern : " + date);


//formatting Date with time information
DATE_FORMAT = new SimpleDateFormat("dd-MM-yy:HH:mm:SS");
date = DATE_FORMAT.format(today);
System.out.println("Today in dd-MM-yy:HH:mm:SS : " + date);


//SimpleDateFormat example - Date with timezone information
DATE_FORMAT = new SimpleDateFormat("dd-MM-yy:HH:mm:SS Z");
date = DATE_FORMAT.format(today);
System.out.println("Today in dd-MM-yy:HH:mm:SSZ : " + date);


}


}

Output:

Today is : Fri Nov 02 16:11:27 IST 2012

Today in dd-MM-yyyy format : 02-11-2012

Today in dd/MM/yy pattern : 02/11/12

Today in dd-MM-yy:HH:mm:SS : 02-11-12:16:11:316

Today in dd-MM-yy:HH:mm:SSZ : 02-11-12:16:11:316 +0530

kk = Hours in 1-24 format
hh= hours in 1-12 format
KK= hours in 0-11 format
HH= hours in 0-23 format

IN two lines:

SimpleDateFormat simpleDateFormat=new SimpleDateFormat("hh:mm aa",Locale.getDefault());
FAJR = new SimpleDateFormat("HH:mm",Locale.getDefault()).format(simpleDateFormat.parse("8:35 PM");

This is a method that uses JODA.

Input example is 07/20/2015 01:46:34.436 AM

public static String get24HourFormat(String dateString){
Date date = new Date();
DateTime date1=new DateTime();


//  String date="";
int hour=0;
//int year=0;
if(dateString!=null){


try {
DateTimeFormatter formatter = DateTimeFormat.forPattern("MM/dd/yyyy hh:mm:ss.SSS aa");
DateTimeFormatter output = DateTimeFormat.forPattern("kk");


date1=formatter.parseDateTime(dateString);
hour=date1.getHourOfDay();
System.out.println(output.print(date1));
//  System.out.println(date);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return hour+"";
}

With Calendar it works as follows:

    //create first Calendar object
Calendar calendar = Calendar.getInstance();


calendar.set(Calendar.HOUR_OF_DAY, 15); // 3 PM
// the same is
calendar.set(Calendar.AM_PM, Calendar.PM); // choose PM mode
calendar.set(Calendar.HOUR, 3); // 3 PM


System.out.println( calendar.get(Calendar.HOUR) ); // AM_PM format
System.out.println( calendar.get(Calendar.HOUR_OF_DAY) ); // 0-23 format

    DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");


Date date = new Date();
Date date2 = new Date("2014/08/06 15:59:48");


String currentDate = dateFormat.format(date).toString();
String anyDate = dateFormat.format(date2).toString();


System.out.println(currentDate);
System.out.println(anyDate);