Dinesh on Java

Date is a class in java.util package in java. It represent date of the day with time stamp. But in the application we need to display the date upfront in the String format. So it is very common requirement to convert Date to String. So we need to convert java.util.Date to string in java for displaying purpose. In there are various way of converting Date to String by using SimpleDateFormat class in java. Actually there are two classes in java.text package DateFormat and SimpleDateFormat and they are very powerful and you can use one of them for Date to String conversion.

Here we are discussing an example of converting Date to String by using SimpleDateFormat. Let’s see following steps:

• Step 1: Create a valid date format using SimpleDateFormat as you wanna display upfront
• Step 2: Then call format() method of SimpleDateFormat and passed Date object as argument of this method, it will return String format of date as you specified in the first step.

For Example:

public static void main(String[] args) {
  //Creating Date in java with today's date.
  Date todayDate = new Date();

  //change date to string on dd-MM-yyyy format e.g. "20-02-2017"
  SimpleDateFormat dateformater_Java = new SimpleDateFormat("dd-MM-yyyy");
  String todayDateStr = dateformater_Java.format(todayDate);
  System.out.println("Today's date into dd-MM-yyyy format: " + todayDateStr);
  
  //converting date to string dd/MM/yyyy format for example "20/02/2017"
  SimpleDateFormat formatDateJava = new SimpleDateFormat("dd/MM/yyyy");
  todayDateStr = formatDateJava.format(todayDate);
  System.out.println("Today's date into dd/MM/yyyy format: " + todayDateStr);
    
  //change date into string yyyyMMdd format example "20170220"
  SimpleDateFormat dateformater_yyyyMMdd = new SimpleDateFormat("yyyyMMdd");
  todayDateStr = dateformater_yyyyMMdd.format(todayDate);
  System.out.println("Today's date into yyyyMMdd format: " + todayDateStr);

  //converting  date into ddMMyyyy format example "20022017"
  SimpleDateFormat dateformater_ddMMyyyy = new SimpleDateFormat("ddMMyyyy");
  todayDateStr = dateformater_ddMMyyyy.format(todayDate);
  System.out.println("Today's date into ddMMyyyy format: " + todayDateStr);
    
  //date to dd-MMM-yy format e.g. "20-Feb-17"
  SimpleDateFormat ddMMMyyFormat = new SimpleDateFormat("dd-MMM-yy");
  todayDateStr = ddMMMyyFormat.format(todayDate);
  System.out.println("Today's date into dd-MMM-yy format: " + todayDateStr);

  //convert date to dd-MMMM-yy format e.g. "20-August-17"
  SimpleDateFormat ddMMMMyyFormat = new SimpleDateFormat("dd-MMMM-yy");
  todayDateStr = ddMMMMyyFormat.format(todayDate);
  System.out.println("Today's date into dd-MMMM-yy format: " + todayDateStr);
 }

Output:
Today’s date into dd-MM-yyyy format: 20-02-2017
Today’s date into dd/MM/yyyy format: 20/02/2017
Today’s date into yyyyMMdd format: 20170220
Today’s date into ddMMyyyy format: 20022017
Today’s date into dd-MMM-yy format: 20-Feb-17
Today’s date into dd-MMMM-yy format: 20-February-17

SimpleDateFromat Java Doc
SimpleDateFormat is a concrete class for formatting and parsing dates in a locale-sensitive manner. It allows for formatting (date -> text), parsing (text -> date), and normalization. SimpleDateFormat allows you to start by choosing any user-defined patterns for date-time formatting.

SimpleDateFormat is an excellent utility for converting String to Date and then Date to String. It is not thread-safe so its better you create separate DateFormat for each thread to avoid any race condition while parsing date in java.

There are some designator of SimpleDateFormat
y -> Year Year 1996; 96
M -> Month in year Month July; Jul; 07
w -> Week in year Number 27
W -> Week in month Number 2
D -> Day in year Number 189
d -> Day in month Number 10
a -> Am/pm marker Text PM
H -> Hour in day (0-23) Number 0
h -> Hour in am/pm (1-12) Number 12
m -> Minute in hour Number 30
s -> Second in minute Number 55
S -> Millisecond Number 978

Summary
In this tutorial we have seen how to convert Date to String. Format of date in String is depends to the developer but developer can use predefined pattern letters. We careful about like “m” and “M”, there are some letter are small case and same letter also available in capital case so they confused to developer some time.