How to add minutes to date in java

Question

I have date in string variable, i have to add/subtract minutes from it, please adivce , how i could do in java 1.5
sample data
String olddate = "12/16/2010 4:58:29 PM"
String minutes1 = "300"
i would like to get value as below for above data
String newdate ="12/16/2010 9:58:29 PM"

Answer 1

Use SimpleDateFormat to convert the date object to string. Once the string object converted to date object use the getTime() method to get the date in milliseconds.
Now you can easily adds/substract the date object.
Remember, the resulting long value from getTime() method is in milliseconds, to get the value in minutes you need to multiply it by 1000 and by seconds in a minutes, that is 60.
When your subtraction/adds done convert it back to date object.
This is the codes:
import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Date;
public class DateCalculator {
     public static void main(String[] args) throws ParseException {
          String olddate = "12/16/2010 4:58:29 PM";
          System.out.println("old Date: "+olddate);
          SimpleDateFormat formatter = new SimpleDateFormat("MM/dd/yyyy h:mm:ss a");
          long oldDateInMillis = formatter.parse(olddate).getTime();
          String minutes1 = "300";
          String newDateAdds = formatter.format(new Date(oldDateInMillis + Long.valueOf(minutes1)*1000*60 ));
          String newDateSubstract = formatter.format(new Date(oldDateInMillis - Long.valueOf(minutes1)*1000*60 ));
          System.out.println("new Date [Additions] : "+newDateAdds);
          System.out.println("new Date [Substraction] : "+newDateSubstract);
}