Java SimpleDateFormat - Java Date Format

Introduction

Java SimpleDateFormat and DateFormat classes are used for date formatting. It is mostly used where we need to display or utilize the date and time functionality of Java. Both of these classes are present in com.text package.

Java DateFormat

• DateFormat is used for formatting a date into String based on specific locale that is provided as input.
• The locale is used for specifying the region and language for making the code more locale to the user.
• The way of writing date is different in different regions of the world. For example, 31st Dec 2017 will be written in India as 31-12-2017 but the same thing will be written in the United States of America as 12-31-2017.
• DateFormat classes are not synchronized, it’s recommended to create separate instance for each thread.

A DateFormat object can be created using the getDateInstance() and getTimeInstance() method of the DateFormat class.

Locale loc = new Locale("en", "US");
DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.DEFAULT, loc);

Locale loc = new Locale.Builder().setLanguage("en").setRegion("US").build();

The getDateInstance method of DateFormat needs two input parameters. The first parameter specifies the DateFormat to use and the second parameter is the locale.

Using format

DateFormat class has a format method which is responsible for formatting.

Locale locale = new Locale("fr", "FR");
DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.DEFAULT, locale);
String date = dateFormat.format(new Date());
System.out.print(date);

This code will format the date in the French (fr) language and the France (FR) region:

Output
3 janv. 2018

Using getTimeInstance()

For creating a DateFormat instance we are using getDateInstance() method.

For performing a time format, we need an instance of time. We will be using getTimeInstance() method for getting an instance of time.

Locale locale = new Locale("fr", "FR");
DateFormat dateFormat = DateFormat.getTimeInstance(DateFormat.DEFAULT, locale);
String date = dateFormat.format(new Date());
System.out.print(date);

This code will format the time in the French (fr) language and the France (FR) region:

Output
11:03:01

Java SimpleDateFormat

SimpleDateFormat is similar to DateFormat. The only major difference between them is that SimpleDateFormat can be used for formatting (Date to String conversion) and for parsing (String to Date conversion) with locale support, whereas DateFormat don’t have locale support. DateFormat is an abstract class that provides base support for date formatting and parsing. SimpleDateFormat is the concrete class that extends DateFormat class.

SimpleDateFormat can be created using the SimpleDateFormat constructor. The constructor is a parametrised constructor and needs a String pattern as the parameter.

String pattern = "MM-dd-yyyy";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);

The String pattern is the pattern which will be used to format a date and the output will be generated in that pattern as “MM-dd-yyyy”.

Patterns

Let us have a look at the pattern syntax that should be used for the formatting pattern.

Some letters should be used in different amount for different results like for month:

Examples

Let us now look at some examples for different formats of date and time.

Using SimpleDateFormat()

In order to parse a date we need to create an instance of SimpleDateFormat using the constructor and then use the format() method:

String pattern = "MM-dd-yyyy";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);
String date = simpleDateFormat.format(new Date());
System.out.println(date);

This code will output “MM-dd-yyyy”:

Output
01-02-2018

This pattern produces “month in year”, “day in month”, and “year”. The type of character (and capitalization) and the amount of characters contribute to the string. The month would be represented as two digits, the day as two digits, and the year as four digits.

This code displayed the date of “January 2, 2018” as “01-02-2018”.

For parsing time, we have to change the pattern while creating SimpleDateFormat instance.

String pattern = "HH:mm:ss.SSSZ";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);
String date = simpleDateFormat.format(new Date());
System.out.println(date);

This code will output “HH:mm:ss.SSSZ”:

Output
13:03:15.454+0530

This pattern produces “hours”, “minutes”, “seconds”, “milliseconds”, and “timezone offset in hours (RFC pattern)”.

This code displayed the time as “13:03:15.454+0530”.

Using parse()

Parsing is the conversion of String into a java.util.Date instance. We can parse a string to a date instance using parse() method of the SimpleDateFormat class. For parsing a String to Date we need an instance of the SimpleDateFormat class and a string pattern as input for the constructor of the class.

String pattern = "MM-dd-yyyy";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);
Date date = simpleDateFormat.parse("12-01-2018");
System.out.println(date);

This will output a date (12-01-2018) without a specified time:

Output
Sat Dec 01 00:00:00 IST 2018

Now let’s look at SimpleDateFormat example to parse time.

String pattern = "HH:mm:ss";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);
Date date = simpleDateFormat.parse("22:00:03");
System.out.println(date);

This will output a time (22:00:03) without a specified date:

Output
Thu Jan 01 22:00:03 IST 1970

Because we have not specified any date the program considered epoch as the date (i.e., 01-Jan-1970).

Using Locale

We have worked with Locale as part of the DateFormat and we have seen that locales are used based on regions.

String pattern = "EEEEE MMMMM yyyy HH:mm:ss.SSSZ";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern, new Locale("fr", "FR"));
Date date = simpleDateFormat.format(new Date());
System.out.println(date);

This code will format the current time in the French (fr) language and the France (FR) region:

Output
mardi janvier 2018 14:51:02.354+0530

The day and month are named in French based on the Locale provided as input - mardi is “Tuesday” and janvier is “January”.

Conclusion

In this article, you learned about Java’s SimpleDateFormat and DateFormat.

Reference:

• SimpleDateFormat API Doc
• DateFormat API Doc