Java Date Time Formate

Java's java.util package provides Date classes that encapsulate the current date and time. The Date class supports two constructors, as shown in the following table.

Following is the list of methods of the Date class −

1. Get the current date and time

Here's an easy way to get the current date and time in Java. You can use Date object toString()methods to print the current date and time as follows −

import java.util.Date;
public class Test {

   public static void main(String args[]) {
     
      Date date = new Date();

      // display time and date using toString()
      System.out.println(date.toString());
   }
}

Execute the above sample code and get the following results:

Fri Mar 15 13:00:37 CST 2020

2. Use SimpleDateFormat to set the date format

SimpleDateFormat is a concrete class for formatting and parsing dates in the locale's way. SimpleDateFormatUsed to select from user-defined patterns for datetime formats.

Example

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

public class Test {

    public static void main(String args[]) {
        Date dNow = new Date();
        SimpleDateFormat ft = new SimpleDateFormat("yyyy.MM.dd (E)'at' hh:mm:ss a zzz");

        System.out.println("Current Date: " + ft.format(dNow));

        SimpleDateFormat ft2 = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

        System.out.println("Current Datetime: " + ft2.format(dNow));

    }
}

Execute the above sample code and get the following results:

Current Date: 2023.01.05 (Thu)at 12:43:45 PM UTC

Current Datetime: 2023-01-05 12:43:45

DateFormat format code

To specify a time format, use a time pattern string. In this mode, all ASCII letters are reserved as pattern letters, which are defined as follows −

3. Java Format Date Using printf

Date and time formatting is done using printf methods. Use the two-letter format, t beginning with and ending with a letter of the form, as shown in the code below.

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

public class Test {

    public static void main(String args[]) {
        // Instantiate a Date object
        Date date = new Date();

        // display time and date
        String str = String.format("Current Date/Time : %tc", date);

        System.out.printf(str);

    }
}

Execute the above sample code and get the following results:

Current Date/Time : Thu Jan 05 12:44:52 UTC 2023

It would be somewhat silly to provide the date multiple times to format each part. A string format may indicate the index of the parameter to be formatted.

The index must follow % and must $ end with .

example

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

public class Test {

    public static void main(String args[]) {
        // Instantiate a Date object
        Date date = new Date();

        // display time and date
        System.out.printf("%1$s %2$tB %2$td, %2$tY", "Due date:", date);
    }
}

Execute the above sample code and get the following results:

Due date: January 05, 2023

Alternatively, < flags can be used. It says again to use the same parameters as the previous format specification.

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

public class Test {

    public static void main(String args[]) {
        // Instantiate a Date object
        Date date = new Date();

        // display formatted date
        System.out.printf("%s %tB %<te, %<tY", "Due date:", date);
    }
}

Execute the above sample code and get the following results:

Due date: January 5, 2023

example

There are other useful classes related to dates and times. See the Java Standards documentation for more details.

5. How do I parse the String into Date in Java 

SimpleDateFormat The class has some additional methods, in particular parse(), it is used to parse the string according to the format stored in the given SimpleDateFormat object.

Example

import java.util.*;
import java.text.*;

public class Test {

    public static void main(String args[]) {
        SimpleDateFormat ft = new SimpleDateFormat("yyyy-MM-dd");
        String input = args.length == 0 ? "2021-11-11" : args[0];

        System.out.print(input + " Format：");
        Date t;
        try {
            t = ft.parse(input);
            System.out.println(t);
        } catch (ParseException e) {
            System.out.println("Unparseable using " + ft);
        }
    }
}

Execute the above sample code and get the following results:

2021-11-11Thu Nov 11 00:00:00 UTC 2021

6. How do i print delay with 1 second in java 

Sleep can occur during any period of the computer's lifecycle. For example, the following program will sleep 3 for seconds -

import java.util.*;
import java.text.*;

public class Test {

    public static void main(String args[]) {
        try {
            System.out.println(new Date());
            Thread.sleep(5 * 60 * 10);
            System.out.println(new Date());
        } catch (Exception e) {
            System.out.println("Got an exception!");
        }
    }
}

Execute the above sample code and get the following results:

Thu Jan 05 12:56:37 UTC 2023
Thu Jan 05 12:56:40 UTC 2023

7. How do i Measure elapsed time in Java

Sometimes, it may be necessary to measure time points in milliseconds. Rewriting the above example 

import java.util.*;
import java.text.*;

public class Test {

    public static void main(String args[]) {
        try {
            long start = System.currentTimeMillis();
            System.out.println(new Date());

            Thread.sleep(5 * 60 * 10);
            System.out.println(new Date());

            long end = System.currentTimeMillis();
            long diff = end - start;
            System.out.println("Difference is: " + diff);
        } catch (Exception e) {
            System.out.println("Got an exception!");
        }
    }
}

Execute the above sample code and get the following results:

Thu Jan 05 12:58:40 UTC 2023
Thu Jan 05 12:58:43 UTC 2023
Difference is: 3115

8. What is Gregorian Calendar Class

Gregorian Calendar is a concrete implementation of a Calendar class that implements the normal Gregorian calendar with which we are familiar. Here we are just learn the methods of Gregorian Calenar class. More about Breborian calendar you can read at Java documentation for this.

How to get GregorianCalendar in Java

The getInstance( ) method of Calendar returns a Gregorian Calendar initialized with the current date and time in the default locale and time zone. Gregorian Calendar defines two fields: AD and BC. These represent the two eras defined by the Gregorian calendar.

There are also several constructors for GregorianCalendar objects −

Below are the the list of few useful support methods provided by Gregorian Calendar class