Change date format in a Java string

Question

I've a String representing a date.

String date_s = "2011-01-18 00:00:00.0";

I'd like to convert it to a Date and output it in YYYY-MM-DD format.

2011-01-18

How can I achieve this?

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Okay, based on the answers I retrieved below, here's something I've tried:

String date_s = " 2011-01-18 00:00:00.0"; 
SimpleDateFormat dt = new SimpleDateFormat("yyyyy-mm-dd hh:mm:ss"); 
Date date = dt.parse(date_s); 
SimpleDateFormat dt1 = new SimpleDateFormat("yyyyy-mm-dd");
System.out.println(dt1.format(date));

But it outputs 02011-00-1 instead of the desired 2011-01-18. What am I doing wrong?

Answer 1

The answer is of course to create a SimpleDateFormat object and use it to parse Strings to Date and to format Dates to Strings. If you've tried SimpleDateFormat and it didn't work, then please show your code and any errors you may receive.

Addendum: "mm" in the format String is not the same as "MM". Use MM for months and mm for minutes. Also, yyyyy is not the same as yyyy. e.g.,:

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

public class FormateDate {

    public static void main(String[] args) throws ParseException {
        String date_s = "2011-01-18 00:00:00.0";

        // *** note that it's "yyyy-MM-dd hh:mm:ss" not "yyyy-mm-dd hh:mm:ss"  
        SimpleDateFormat dt = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        Date date = dt.parse(date_s);

        // *** same for the format String below
        SimpleDateFormat dt1 = new SimpleDateFormat("yyyy-MM-dd");
        System.out.println(dt1.format(date));
    }

}

Answer 2

You can use LocalDateTime#parse() or ZonedDateTime#parse(), to parse a String in a certain pattern into a LocalDateTime.

String oldstring = "2011-01-18 00:00:00.0";
LocalDateTime datetime = LocalDateTime.parse(oldstring, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.S"));

Either you can use LocalDateTime#format() (or ZonedDateTime#format()) to format a LocalDateTime into a String in a certain pattern.

String newstring = datetime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
System.out.println(newstring); // 2011-01-18

Answer 3

The reason for the inaccuracy is because you are not using LocalDateTime#parse() or even ZonedDateTime#parse(). Also, if the string happens to contain a time zone part), then you will need to parse a String in a certain pattern into a LocalDateTime. Refer below for more clarification:-

String oldstring = "2011-01-18 00:00:00.0"; LocalDateTime datetime = LocalDateTime.parse(oldstring, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.S"));

If you're not on Java 8 yet, the simple use of SimpleDateFormat#parse() to parse a String in a certain pattern into a Date as shown below will help you:-
 

String oldstring = "2011-01-18 00:00:00.0"; Date date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.S").parse(oldstring);

Trying incorporating the SimpleDateFormat#format() to format a Date into a String in a certain pattern as shown below:-
 

String newstring = new SimpleDateFormat("yyyy-MM-dd").format(date); System.out.println(newstring); // 2011-01-18