Question

I have a string with dates it looks like: “20120316 20120317 20120318” … I store this dates in this format, but I would like to make a Date array from these numbers with the format 03/16 03/17 03/18 …

So far:

 String[] DailyDatasOnce2 = DatesOnce.split(" ");   

         DailyDatasOnce = new String[DailyDatasOnce2.length];
         for (int i=0;i< (DailyDatasOnce2.length) ;i++){
             DailyDatasOnce[i]=DailyDatasOnce2[i];
         }

         datumok = new Date[DailyDatasOnce.length];

         for (int i=0;i< (DailyDatasOnce.length) ;i++){

            SimpleDateFormat curFormater = new SimpleDateFormat("yyyyMMdd"); 

            java.util.Date dateObj = null;
            java.util.Date dateObj2 = null;
            try {
                dateObj = curFormater.parse(DailyDatasOnce[i]);
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
            SimpleDateFormat postFormater = new SimpleDateFormat("MM/dd"); 

            String newDateStr = postFormater.format(dateObj); 

            try {
                dateObj2 = curFormater.parse(newDateStr);
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
            datumok[i] = dateObj2;

         }

So first I make a string array with the string dates (DailyDatasOnce), maybe that first for loop is useless but i can skip it. Now I make a Date array and I want to put the dates into it. I format the dates to format I want, then I try to convert them to Date format. Until the String newDateStr it is working, I manage to change the type of the date.
But I get syntax error for the last row: Type mismatch: Cannot convert from java.util.date to java.sql.data.
I suspect the problem but if it is not possible, how can i do this?

Answer 1

Here’s what I recommend:

DateFormat fromFormat = new SimpleDateFormat("yyyyMMdd");
fromFormat.setLenient(false);
DateFormat toFormat = new SimpleDateFormat("MM/dd");
toFormat.setLenient(false);
String fromDate = "20120316";
Date d = fromFormat.parse(fromDate); // this is a java.util.Date
System.out.println(String.format("date is %s", toFormat.format(d));

You don’t need two Dates, just one; you need to and from formats.

It must be java.util.Date.

If you have a collection, just do this:

String [] dateStrings = datesOnce.split(" ");
List<Date> dates = new ArrayList<Date>();
for (String dateString : dateStrings) {
    dates.add(fromFormat.parse(dateString));
}

You can format all those Dates any way you wish.

If it must be a Date array, do it this way:

String [] dateStrings = datesOnce.split(" ");
Date [] dates = new Date[dateStrings.length];
int i = 0; 
for (String dateString : dateStrings) {
    dates[i++] = fromFormat.parse(dateString);
}

Here’s a complete demo:

package homework;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * DateFormatDemo
 * @author Michael
 * @link http://stackoverflow.com/questions/9796520/how-to-convert-string-format-dates-to-date-format-dates/9796619#comment12475521_9796619
 * @since 3/20/12 8:55 PM
 */
public class DateFormatDemo {

    public static void main(String[] args) {
        String input = "20120316 20120317 20120318";
        DateFormat fromFormat = new SimpleDateFormat("yyyyMMdd");
        fromFormat.setLenient(false);
        DateFormat toFormat = new SimpleDateFormat("MM/dd");
        toFormat.setLenient(false);
        String [] dateStrings = input.split("\\s+");
        Date [] dates = new Date[dateStrings.length];
        int i = 0;
        for (String dateString : dateStrings) {
            try {
                dates[i++] = fromFormat.parse(dateString);
            } catch (ParseException e) {
                e.printStackTrace();
            }
        }
        for (Date d : dates) {
            System.out.println(toFormat.format(d));
        }
    }
}