[java] How to convert date to string and to date again?

Hi i want to convert the current date to this format YYYY-MM-DD. However, it will convert the date into String format, but i want to convert it back into Date format. So can anyone advise on this?

This is my code so far

 DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
 Date date = new Date();
 String datestring = dateFormat.format(date); 

For converting date to string check this thread

Convert java.util.Date to String

And for converting string to date try this,

import java.text.ParseException;
import java.text.SimpleDateFormat;

public class StringToDate
{
    public static void main(String[] args) throws ParseException
    {
        SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy hh:mm:ss");
        String strDate = "14/03/2003 08:05:10";     
        System.out.println("Date - " + sdf.parse(strDate));
    }
}

Convert Date to String using this function

public String convertDateToString(Date date, String format) {
        String dateStr = null;
        DateFormat df = new SimpleDateFormat(format);
        try {
            dateStr = df.format(date);
        } catch (Exception ex) {
            System.out.println(ex);
        }
        return dateStr;
    }

From Convert Date to String in Java . And convert string to date again

public Date convertStringToDate(String dateStr, String format) {
        Date date = null;
        DateFormat df = new SimpleDateFormat(format);
        try {
            date = df.parse(dateStr);
        } catch (Exception ex) {
            System.out.println(ex);
        }
        return date;
    }

From Convert String to date in Java

try this function

public static Date StringToDate(String strDate) throws ModuleException {
    Date dtReturn = null;
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-mm-dd");
    try {
        dtReturn = simpleDateFormat.parse(strDate);
    } catch (ParseException e) {
        e.printStackTrace();
    }
    return dtReturn;
}

tl;dr

How to convert date to string and to date again?

LocalDate.now().toString()

2017-01-23

…and…

LocalDate.parse( "2017-01-23" )

java.time

The Question uses troublesome old date-time classes bundled with the earliest versions of Java. Those classes are now legacy, supplanted by the java.time classes built into Java 8, Java 9, and later.

Determining today’s date requires a time zone. For any given moment the date varies around the globe by zone.

If not supplied by you, your JVM’s current default time zone is applied. That default can change at any moment during runtime, and so is unreliable. I suggest you always specify your desired/expected time zone.

ZoneId z = ZoneId.of( "America/Montreal" ) ;
LocalDate ld = LocalDate.now( z ) ;

ISO 8601

Your desired format of YYYY-MM-DD happens to comply with the ISO 8601 standard.

That standard happens to be used by default by the java.time classes when parsing/generating strings. So you can simply call LocalDate::parse and LocalDate::toString without specifying a formatting pattern.

String s = ld.toString() ;

To parse:

LocalDate ld = LocalDate.parse( s ) ;

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Use DateFormat#parse(String):

Date date = dateFormat.parse("2013-10-22");