Date | Kode Java

How do I set the time of java.util.Date instance to 00:00:00?

By Wayan in Core API, Util Package Last modified: July 10, 2023 1 Comment

The following code snippet shows you how to remove time information from the java.util.Date object. The static method removeTime() in the code snippet below will take a Date object as parameter and will return a new Date object where the hour, minute, second and millisecond information have been reset to zero. To do this we use the java.util.Calendar. To remove time information, we set the calendar fields of Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND to zero.

package org.kodejava.util;

import java.util.Calendar;
import java.util.Date;

public class DateRemoveTime {
    public static void main(String[] args) {
        System.out.println("Now = " + removeTime(new Date()));
    }

    private static Date removeTime(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        return calendar.getTime();
    }
}

The result of the code snippet above is:

Now = Sat Nov 20 00:00:00 CST 2021

How to convert java.time.LocalDate to java.util.Date?

By Wayan in Date Time Last modified: July 4, 2023 2 Comments

The following code snippet demonstrate how to convert java.time.LocalDate to java.util.Date and vice versa. In the first part of the code snippet we convert LocalDate to Date and back to LocalDate object. On the second part we convert LocalDateTime to Date and back to LocalDateTime object.

package org.kodejava.datetime;

import java.time.*;
import java.util.Date;

public class LocalDateToDate {
    public static void main(String[] args) {
        // Convert java.time.LocalDate to java.util.Date and back to
        // java.time.LocalDate
        LocalDate localDate = LocalDate.now();
        System.out.println("LocalDate = " + localDate);

        Date date1 = Date.from(localDate.atStartOfDay(ZoneId.systemDefault()).toInstant());
        System.out.println("Date      = " + date1);

        localDate = date1.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
        System.out.println("LocalDate = " + localDate);
        System.out.println();

        // Convert java.time.LocalDateTime to java.util.Date and back to
        // java.time.LocalDateTime
        LocalDateTime localDateTime = LocalDateTime.now();
        System.out.println("LocalDateTime = " + localDateTime);

        Date date2 = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
        System.out.println("Date          = " + date2);

        localDateTime = date2.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
        System.out.println("LocalDateTime = " + localDateTime);
    }
}

The result of the code snippet:

LocalDate = 2021-11-20
Date      = Sat Nov 20 00:00:00 CST 2021
LocalDate = 2021-11-20

LocalDateTime = 2021-11-20T18:25:05.706380200
Date          = Sat Nov 20 18:25:05 CST 2021
LocalDateTime = 2021-11-20T18:25:05.706

How do I convert between old Date and Calendar object with the new Java 8 Date Time?

By Wayan in Date Time Last modified: June 30, 2023 0 Comment

In this example we will learn how to convert the old java.util.Date and java.util.Calendar objects to the new Date Time introduced in Java 8. The first method in the code snippet below dateToNewDate() show conversion of java.util.Date while the calendarToNewDate() show the conversion of java.util.Calendar.

The java.util.Date and java.util.Calendar provide a toInstant() method to convert the objects to the new Date Time API class of the java.time.Instant. To convert the old date into the Java 8 LocalDate, LocalTime and LocalDateTime we first can create an instance of ZonedDateTime using the atZone() method of the Instant class.

ZonedDateTime zonedDateTime = instant.atZone(ZoneId.systemDefault());

From an instance of ZonedDateTime class we can call the toLocalDate(), toLocalTime() and toLocalDateTime() to get instance of LocalDate, LocalTime and LocalDateTime.

To convert back from the new Java 8 date to the old java.util.Date we can use the Date.from() static factory method and passing and instance of java.time.Instant that we can obtain by calling the following code.

Instant instant1 = dateTime.atZone(ZoneId.systemDefault()).toInstant();
Date now1 = Date.from(instant1);

Here are the complete code snippet to convert java.util.Date to the new Java 8 Date Time.

private static void dateToNewDate() {
    Date now = new Date();
    Instant instant = now.toInstant();

    ZonedDateTime zonedDateTime = instant.atZone(ZoneId.systemDefault());

    LocalDate date = zonedDateTime.toLocalDate();
    LocalTime time = zonedDateTime.toLocalTime();
    LocalDateTime dateTime = zonedDateTime.toLocalDateTime();

    Instant instant1 = dateTime.atZone(ZoneId.systemDefault()).toInstant();
    Date now1 = Date.from(instant1);

    System.out.println("java.util.Date          = " + now);
    System.out.println("java.time.LocalDate     = " + date);
    System.out.println("java.time.LocalTime     = " + time);
    System.out.println("java.time.LocalDateTime = " + dateTime);
    System.out.println("java.util.Date          = " + now1);
    System.out.println();
}

The steps for converting from the java.util.Calendar to the new Java 8 date can be seen in the code snippet below. As with java.util.Date the Calendar class provide toInstant() method to convert the calendar to java.time.Instant object.

Using the LocalDateTime.ofInstant() method we can create a LocalDateTime object from the instant object. By having the LocalDateTime object we can then get an instance of LocalDate and LocalTime by calling the toLocalDate() and toLocalTime() method.

Finally, to convert back to java.util.Calendar we can use the GregorianCalendar.from() static factory method which require an instance of ZonedDateTime to be passed as a parameter. To get an instance of ZonedDateTime we can call LocalDateTime.atZone() method. You can see the complete code in the code snippet below.

private static void calendarToNewDate() {
    Calendar now = Calendar.getInstance();

    LocalDateTime dateTime = LocalDateTime.ofInstant(now.toInstant(),
            ZoneId.systemDefault());

    LocalDate date = dateTime.toLocalDate();
    LocalTime time = dateTime.toLocalTime();

    ZonedDateTime zonedDateTime = dateTime.atZone(ZoneId.systemDefault());
    Calendar now1 = GregorianCalendar.from(zonedDateTime);

    System.out.println("java.util.Calendar      = " + now);
    System.out.println("java.time.LocalDateTime = " + dateTime);
    System.out.println("java.time.LocalDate     = " + date);
    System.out.println("java.time.LocalTime     = " + time);
    System.out.println("java.util.Calendar      = " + now1);
}

Below is the main Java class to run the code snippet. You must place the above methods inside this class to run the code snippet.

package org.kodejava.datetime;

import java.time.*;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class LegacyDateCalendarToNewDateExample {
    public static void main(String[] args) {
        dateToNewDate();
        calendarToNewDate();
    }
}

Here are the result of the code snippet above. The first group is conversion the java.util.Date to the new Date Time API. The second group is conversion from the java.util.Calendar to the new Date Time API.

java.util.Date          = Tue Nov 16 08:44:51 CST 2021
java.time.LocalDate     = 2021-11-16
java.time.LocalTime     = 08:44:51.031
java.time.LocalDateTime = 2021-11-16T08:44:51.031
java.util.Date          = Tue Nov 16 08:44:51 CST 2021

java.util.Calendar      = java.util.GregorianCalendar[time=1637023491089,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=31,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2021,MONTH=10,WEEK_OF_YEAR=47,WEEK_OF_MONTH=3,DAY_OF_MONTH=16,DAY_OF_YEAR=320,DAY_OF_WEEK=3,DAY_OF_WEEK_IN_MONTH=3,AM_PM=0,HOUR=8,HOUR_OF_DAY=8,MINUTE=44,SECOND=51,MILLISECOND=89,ZONE_OFFSET=28800000,DST_OFFSET=0]
java.time.LocalDateTime = 2021-11-16T08:44:51.089
java.time.LocalDate     = 2021-11-16
java.time.LocalTime     = 08:44:51.089
java.util.Calendar      = java.util.GregorianCalendar[time=1637023491089,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=31,lastRule=null],firstDayOfWeek=2,minimalDaysInFirstWeek=4,ERA=1,YEAR=2021,MONTH=10,WEEK_OF_YEAR=46,WEEK_OF_MONTH=3,DAY_OF_MONTH=16,DAY_OF_YEAR=320,DAY_OF_WEEK=3,DAY_OF_WEEK_IN_MONTH=3,AM_PM=0,HOUR=8,HOUR_OF_DAY=8,MINUTE=44,SECOND=51,MILLISECOND=89,ZONE_OFFSET=28800000,DST_OFFSET=0]

How do I checks if two dates are on the same day?

By Wayan in Apache Commons, Commons Lang Last modified: June 5, 2023 0 Comment

In this example you’ll learn how to find out if two defined date objects are on the same day. It means that we are only interested in the date information and ignoring the time information of these date objects. We’ll be using an API provided by the Apache Commons Lang in this example. So here is the code snippet:

package org.kodejava.commons.lang;

import org.apache.commons.lang3.time.DateUtils;

import java.util.Calendar;
import java.util.Date;

public class CheckSameDay {
    public static void main(String[] args) {
        Date date1 = new Date();
        Date date2 = new Date();

        // Checks to see if the dates is on the same day.
        if (DateUtils.isSameDay(date1, date2)) {
            System.out.printf("%1$te/%1$tm/%1$tY and %2$te/%2$tm/%2$tY " +
                    "is on the same day.%n", date1, date2);
        }

        Calendar cal1 = Calendar.getInstance();
        Calendar cal2 = Calendar.getInstance();

        // Checks to see if the calendars is on the same day.
        if (DateUtils.isSameDay(cal1, cal2)) {
            System.out.printf("%1$te/%1$tm/%1$tY and %2$te/%2$tm/%2$tY " +
                    "is on the same day.%n", cal1, cal2);
        }

        cal2.add(Calendar.DAY_OF_MONTH, 10);
        if (!DateUtils.isSameDay(cal1, cal2)) {
            System.out.printf("%1$te/%1$tm/%1$tY and %2$te/%2$tm/%2$tY " +
                    "is not on the same day.", cal1, cal2);
        }
    }
}

The example result produced by this snippet are:

31/10/2021 and 31/10/2021 is on the same day.
31/10/2021 and 31/10/2021 is on the same day.
31/10/2021 and 10/11/2021 is not on the same day.

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.12.0</version>
</dependency>

How do I convert string to Date in GMT timezone?

By Wayan in Core API, Text Package Last modified: June 2, 2023 0 Comment

The following code snippet convert a string representation of a date into a java.util.Date object and the timezone is set to GMT. To parse the string so that the result is in GMT you must set the TimeZone of the DateFormat object into GMT.

package org.kodejava.joda;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

public class WithTimezoneStringToDate {
    public static void main(String[] args) {
        // Create a DateFormat and set the timezone to GMT.
        DateFormat df = new SimpleDateFormat("E, dd MMM yyyy HH:mm:ss z");
        df.setTimeZone(TimeZone.getTimeZone("GMT"));

        try {
            // Convert string into Date
            Date today = df.parse("Fri, 29 Oct 2021 00:00:00 GMT+08:00");
            System.out.println("Today = " + df.format(today));
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

The code snippet above print the following output:

Today = Thu, 28 Oct 2021 16:00:00 GMT

How do I get pattern string of a SimpleDateFormat?

By Wayan in Core API, Text Package Last modified: June 1, 2023 0 Comment

To format a java.util.Date object we use the SimpleDateFormat class. To get back the string pattern that were used to format the date we can use the toPattern() method of this class.

package org.kodejava.text;

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

public class SimpleDateFormatToPattern {
    public static void main(String[] args) {
        SimpleDateFormat format = new SimpleDateFormat("EEEE, dd/MM/yyyy");

        // Gets a pattern string describing this date format used by the
        // SimpleDateFormat object.
        String pattern = format.toPattern();

        System.out.println("Pattern = " + pattern);
        System.out.println("Date    = " + format.format(new Date()));
    }
}

The result of the program will be as follow:

Pattern = EEEE, dd/MM/yyyy
Date    = Tuesday, 26/10/2021

How do I create JSpinner component with date value?

By Wayan in Swing Last modified: May 24, 2023 0 Comment

The SpinnerDateModel allow us to display and select date information from the JSpinner component. By default, the initial value of the model will be set to the current date. To change it we can call the setValue method of the JSpinner object.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;
import java.util.GregorianCalendar;
import java.util.Calendar;

public class JSpinnerDate extends JFrame {
    public JSpinnerDate() {
        initializeUI();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                () -> new JSpinnerDate().setVisible(true));
    }

    private void initializeUI() {
        setSize(500, 500);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        // Create a SpinnerDateModel with current date as the initial value.
        SpinnerDateModel model = new SpinnerDateModel();

        // Set the spinner value to October 9, 2021.
        JSpinner spinner = new JSpinner(model);
        Calendar calendar = new GregorianCalendar(2021, Calendar.OCTOBER, 9);
        spinner.setValue(calendar.getTime());

        getContentPane().add(spinner, BorderLayout.NORTH);
    }
}

How do I convert java.util.Date to java.sql.Date?

By Wayan in JDBC Last modified: July 31, 2023 0 Comment

package org.kodejava.jdbc;

import java.util.Date;

public class UtilDateToSqlDate {
    public static void main(String[] args) {
        // Create a new instance of java.util.Date
        Date date = new Date();

        // To covert java.util.Date to java.sql.Date we need to
        // create an instance of java.sql.Date and pass the long
        // value of java.util.Date as the parameter.
        java.sql.Date sqlDate = new java.sql.Date(date.getTime());

        System.out.println("Date    = " + date);
        System.out.println("SqlDate = " + sqlDate);
    }
}

The result of the code snippet above:

Date    = Sat Oct 09 20:23:27 CST 2021
SqlDate = 2021-10-09

How do I format a message that contains date information?

By Wayan in Core API, Text Package Last modified: May 23, 2023 0 Comment

This example demonstrate how you can use the java.text.MessageFormat class to format a message with a date information in it.

package org.kodejava.text;

import java.util.Date;
import java.util.Calendar;
import java.util.Locale;
import java.text.MessageFormat;

public class MessageFormatDate {
    public static void main(String[] args) {
        Date today = new Date();
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.DATE, 7);

        Date nextWeek = calendar.getTime();

        // We want the message to be is Locale.US
        Locale.setDefault(Locale.US);

        // Format a date, the time value is included
        String message = MessageFormat.format("Today is {0} and next " +
                "week is {1}", today, nextWeek);
        System.out.println(message);

        // Format a date and display only the date portion
        message = MessageFormat.format("Today is {0,date} and next " +
                "week is {1,date}", today, nextWeek);
        System.out.println(message);

        // Format a date using a short format (e.g. dd/MM/yyyy)
        message = MessageFormat.format("Today is {0,date,short} and " +
                "next week is {1,date,short}", today, nextWeek);
        System.out.println(message);

        // Format a date using a medium format, it displays the month long-name,
        // but using a two digit date and year.
        message = MessageFormat.format("Today is {0,date,medium} and " +
                "next week is {1,date,medium}", today, nextWeek);
        System.out.println(message);

        // Format a date using a long format, two digit for date, a long month
        // name and a four digit year.
        message = MessageFormat.format("Today is {0,date,long} and " +
                "next week is {1,date,long}", today, nextWeek);
        System.out.println(message);

        // Format a date using a full format, the same as above plus a full day
        // name.
        message = MessageFormat.format("Today is {0,date,full} and " +
                "next week is {1,date,full}", today, nextWeek);
        System.out.println(message);

        // Format a date using a custom pattern.
        message = MessageFormat.format("Today is {0,date,dd-MM-yyyy} and " +
                "next week is {1,date,dd-MM-yyyy}", today, nextWeek);
        System.out.println(message);
    }
}

The above program produces:

Today is 10/8/21, 9:35 PM and next week is 10/15/21, 9:35 PM
Today is Oct 8, 2021 and next week is Oct 15, 2021
Today is 10/8/21 and next week is 10/15/21
Today is Oct 8, 2021 and next week is Oct 15, 2021
Today is October 8, 2021 and next week is October 15, 2021
Today is Friday, October 8, 2021 and next week is Friday, October 15, 2021
Today is 08-10-2021 and next week is 15-10-2021

How do I add hours, minutes or seconds to a date?

By Wayan in Core API, Util Package Last modified: May 23, 2023 0 Comment

This example shows you how to add or subtract hours, minutes or seconds to a date using the java.util.Calendar object.

package org.kodejava.util;

import java.util.Calendar;

public class DateAddSubtract {
    public static void main(String[] args) {
        // Gets a calendar using the default time zone and locale. The
        // Calendar returned is based on the current time in the default
        // time zone with the default locale.
        Calendar calendar = Calendar.getInstance();
        System.out.println("Original = " + calendar.getTime());

        // Subtract 2 hour from the current time
        calendar.add(Calendar.HOUR, -2);

        // Add 30 minutes to the calendar time
        calendar.add(Calendar.MINUTE, 30);

        // Add 300 seconds to the calendar time
        calendar.add(Calendar.SECOND, 300);
        System.out.println("Updated  = " + calendar.getTime());
    }
}

The output of the code snippet:

Original = Wed Oct 06 19:47:53 CST 2021
Updated  = Wed Oct 06 18:22:53 CST 2021