Check the javadocs for java.text.SimpleDateFormat It describes everything you need.

Use the SimpleDateFormat class:

private Date parseDate(String date, String format) throws ParseException
{
SimpleDateFormat formatter = new SimpleDateFormat(format);
return formatter.parse(date);
}

Usage:

Date date = parseDate("19/05/2009", "dd/MM/yyyy");

For efficiency, you would want to store your formatters in a hashmap. The hashmap is a static member of your util class.

private static Map<String, SimpleDateFormat> hashFormatters = new HashMap<String, SimpleDateFormat>();


public static Date parseDate(String date, String format) throws ParseException
{
SimpleDateFormat formatter = hashFormatters.get(format);


if (formatter == null)
{
formatter = new SimpleDateFormat(format);
hashFormatters.put(format, formatter);
}


return formatter.parse(date);
}

Take a look at SimpleDateFormat. The code goes something like this:

SimpleDateFormat fromUser = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");


try {


String reformattedStr = myFormat.format(fromUser.parse(inputString));
} catch (ParseException e) {
e.printStackTrace();
}

While SimpleDateFormat will indeed work for your needs, additionally you might want to check out Joda Time, which is apparently the basis for the redone Date library in Java 7. While I haven't used it a lot, I've heard nothing but good things about it and if your manipulating dates extensively in your projects it would probably be worth looking into.

Convert a string date to java.sql.Date

String fromDate = "19/05/2009";
DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
java.util.Date dtt = df.parse(fromDate);
java.sql.Date ds = new java.sql.Date(dtt.getTime());
System.out.println(ds);//Mon Jul 05 00:00:00 IST 2010

Simple way to format a date and convert into string

    Date date= new Date();


String dateStr=String.format("%td/%tm/%tY", date,date,date);


System.out.println("Date with format of dd/mm/dd: "+dateStr);

output:Date with format of dd/mm/dd: 21/10/2015

tl;dr

LocalDate.parse(
"19/05/2009" ,
DateTimeFormatter.ofPattern( "dd/MM/uuuu" )
)

Details

The other Answers with java.util.Date, java.sql.Date, and SimpleDateFormat are now outdated.

LocalDate

The modern way to do date-time is work with the java.time classes, specifically LocalDate. The LocalDate class represents a date-only value without time-of-day and without time zone.

DateTimeFormatter

To parse, or generate, a String representing a date-time value, use the DateTimeFormatter class.

DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd/MM/uuuu" );
LocalDate ld = LocalDate.parse( "19/05/2009" , f );

Do not conflate a date-time object with a String representing its value. A date-time object has no format, while a String does. A date-time object, such as LocalDate, can generate a String to represent its internal value, but the date-time object and the String are separate distinct objects.

You can specify any custom format to generate a String. Or let java.time do the work of automatically localizing.

DateTimeFormatter f =
DateTimeFormatter.ofLocalizedDate( FormatStyle.FULL )
.withLocale( Locale.CANADA_FRENCH ) ;
String output = ld.format( f );

Dump to console.

System.out.println( "ld: " + ld + " | output: " + output );

ld: 2009-05-19 | output: mardi 19 mai 2009

See in action in IdeOne.com.

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.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

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
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). 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.

A Date object has no format, it is a representation. The date can be presented by a String with the format you like.

E.g. "yyyy-MM-dd", "yy-MMM-dd", "dd-MMM-yy" and etc.

To acheive this you can get the use of the SimpleDateFormat

Try this,

        String inputString = "19/05/2009"; // i.e. (dd/MM/yyyy) format


SimpleDateFormat fromUser = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");


try {
Date dateFromUser = fromUser.parse(inputString); // Parse it to the exisitng date pattern and return Date type
String dateMyFormat = myFormat.format(dateFromUser); // format it to the date pattern you prefer
System.out.println(dateMyFormat); // outputs : 2009-05-19


} catch (ParseException e) {
e.printStackTrace();
}

This outputs : 2009-05-19

Suppose that you have a string like this :

String mDate="2019-09-17T10:56:07.827088"

Now we want to change this String format separate date and time in Java and Kotlin.

JAVA:

we have a method for extract date :

public String getDate() {
try {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
Date date = dateFormat.parse(mDate);
dateFormat = new SimpleDateFormat("MM/dd/yyyy", Locale.US);
return dateFormat.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}

Return is this : 09/17/2019

And we have method for extract time :

public String getTime() {


try {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
Date date = dateFormat.parse(mCreatedAt);
dateFormat = new SimpleDateFormat("h:mm a", Locale.US);
return dateFormat.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}

Return is this : 10:56 AM

KOTLIN:

we have a function for extract date :

fun getDate(): String? {


var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
val date = dateFormat.parse(mDate!!)
dateFormat = SimpleDateFormat("MM/dd/yyyy", Locale.US)
return dateFormat.format(date!!)
}

Return is this : 09/17/2019

And we have method for extract time :

fun getTime(): String {


var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
val time = dateFormat.parse(mDate!!)
dateFormat = SimpleDateFormat("h:mm a", Locale.US)
return dateFormat.format(time!!)
}

Return is this : 10:56 AM

There are multiple ways to do it, but a very practical one is the use String.format which you can use with java.util.Date or java.util.Calendar or event java.time.LocalDate.

String.format is backed by java.util.Formatter.

I like the omnivore take on it.

class Playground {
public static void main(String[ ] args) {
String formatString = "Created on %1$td/%1$tm/%1$tY%n";
System.out.println(String.format(formatString, new java.util.Date()));
System.out.println(String.format(formatString, java.util.Calendar.getInstance()));
System.out.println(String.format(formatString, java.time.LocalDate.now()));
}
}

The output will be in all cases:

Created on 04/12/2022


Created on 04/12/2022


Created on 04/12/2022