How do I get date and time fields of DateTime object in Joda-Time?

By Wayan in Joda-Time 0 Comment

In Joda-Time the date and time information are divided into fields. The following example show you some fields that can be obtained from the DateTime object. For example to get the day of the year we use the getDayOfYear() method and to get the day of week we can use the getDayOfWeek() method.

package org.kodejava.joda;

import org.joda.time.DateTime;

public class DateTimeFieldDemo {
    public static void main(String[] args) {
        DateTime dateTime = new DateTime();
        System.out.println("DateTime          = " + dateTime);

        // Get day of year, day of month, day of week and week of
        // year of a date.
        System.out.println("Day of Year       = " + dateTime.getDayOfYear());
        System.out.println("Day of Month      = " + dateTime.getDayOfMonth());
        System.out.println("Day of Week       = " + dateTime.getDayOfWeek());
        System.out.println("Week of Week year = " + dateTime.getWeekOfWeekyear());

        // Get hour of day, minute of hour and second of minute.
        System.out.println("Hour of Day       = " + dateTime.getHourOfDay());
        System.out.println("Minute of Hour    = " + dateTime.getMinuteOfHour());
        System.out.println("Second of Minute  = " + dateTime.getSecondOfMinute());

        // Get minute of day and second of day.
        System.out.println("Minute of Day     = " + dateTime.getMinuteOfDay());
        System.out.println("Second of Day     = " + dateTime.getSecondOfDay());
    }
}

The outputs of our program are:

DateTime          = 2021-10-29T06:46:49.259+08:00
Day of Year       = 302
Day of Month      = 29
Day of Week       = 5
Week of Week year = 43
Hour of Day       = 6
Minute of Hour    = 46
Second of Minute  = 49
Minute of Day     = 406
Second of Day     = 24409

Maven Dependencies

<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.12.5</version>
</dependency>

Maven Central

How do I format DateTime object in Joda-Time?

By Wayan in Joda-Time 0 Comment

The example show you how to format the string representation of a date. In Joda we can use the DateTime‘s class toString() method. The method accept the pattern of the date format and the locale information.

package org.kodejava.joda;

import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;

import java.util.Locale;

public class FormattingDemo {
    // Define the date format pattern.
    private static final String pattern = "E MM/dd/yyyy HH:mm:ss.SSS";

    public static void main(String[] args) {
        // Creates a new instance of DateTime object.
        DateTime dt = DateTime.now();

        // Print out the date as a formatted string using the defined
        // Locale information.
        System.out.println("Pattern  = " + pattern);
        System.out.println("Default  = " + dt.toString(pattern));
        System.out.println("Germany  = " + dt.toString(pattern, Locale.GERMANY));
        System.out.println("French   = " + dt.toString(pattern, Locale.FRENCH));
        System.out.println("Japanese = " + dt.toString(pattern, Locale.JAPANESE));

        // Using predefined format from DateTimeFormat class.
        System.out.println("fullDate   = " + dt.toString(DateTimeFormat.fullDate()));
        System.out.println("longDate   = " + dt.toString(DateTimeFormat.longDate()));
        System.out.println("mediumDate = " + dt.toString(DateTimeFormat.mediumDate()));
        System.out.println("shortDate  = " + dt.toString(DateTimeFormat.shortDate()));
        System.out.println("dd/MM/yyyy = " + dt.toString(DateTimeFormat.forPattern("dd/MM/yyyy")));
    }
}

Here are the example result of our program:

Pattern  = E MM/dd/yyyy HH:mm:ss.SSS
Default  = Fri 10/29/2021 06:49:32.491
Germany  = Fr. 10/29/2021 06:49:32.491
French   = ven. 10/29/2021 06:49:32.491
Japanese = 金 10/29/2021 06:49:32.491
fullDate   = Friday, October 29, 2021
longDate   = October 29, 2021
mediumDate = Oct 29, 2021
shortDate  = 10/29/21
dd/MM/yyyy = 29/10/2021

Maven Dependencies

<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.12.5</version>
</dependency>

Maven Central

How do I do a date calculations in Joda-Time?

By Wayan in Joda-Time 0 Comment

Using the Joda-Time library can simplify the date calculation process. For instance, we can add or subtract some days, weeks, months or year easily. There are a plus and minus method for this operation. For instance if you want to add 9 weeks to date object you can do something like date.plusWeeks(9).

package org.kodejava.joda;

import org.joda.time.LocalDate;

public class DateCalculationDemo {
    public static void main(String[] args) {
        // Creates an instance of LocalDate where we are going to do
        // some date calculations.
        LocalDate date = new LocalDate(2021, 10, 29);
        System.out.println("Date           = " + date);

        // Add days, weeks, months, year value into the date object.
        System.out.println("plusDays(10)   = " + date.plusDays(10));
        System.out.println("plusWeeks(9)   = " + date.plusWeeks(9));
        System.out.println("plusMonths(2)  = " + date.plusMonths(2));
        System.out.println("plusYears(1)   = " + date.plusYears(1));

        // Subtract days, weeks, months, year value from date object.
        System.out.println("minusDays(10)  = " + date.minusDays(10));
        System.out.println("minusWeeks(9)  = " + date.minusWeeks(9));
        System.out.println("minusMonths(2) = " + date.minusMonths(2));
        System.out.println("minusYears(1)  = " + date.minusYears(1));
    }
}

The output of the program above are:

Date           = 2021-10-29
plusDays(10)   = 2021-11-08
plusWeeks(9)   = 2021-12-31
plusMonths(2)  = 2021-12-29
plusYears(1)   = 2022-10-29
minusDays(10)  = 2021-10-19
minusWeeks(9)  = 2021-08-27
minusMonths(2) = 2021-08-29
minusYears(1)  = 2020-10-29

Maven Dependencies

<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.12.5</version>
</dependency>

Maven Central

How do I convert Joda-Time’s DateTime into Calendar or Date object?

By Wayan in Joda-Time 0 Comment

This code snippet show you how to convert Joda-Time’s DateTime object into JDK’s java.util.Calendar or java.util.Date object. To convert DateTime to java.util.Date we use the toDate() method and to convert to java.util.Calendar we use the toCalendar() method.

package org.kodejava.joda;

import org.joda.time.DateTime;

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

public class DateTimeToDateCalendarDemo {
    public static void main(String[] args) {
        // Converting DateTime object into JDK's Date.
        DateTime dateTime = DateTime.now();
        Date date = dateTime.toDate();
        System.out.println("org.joda.time.DateTime = " + dateTime);
        System.out.println("java.util.Date         = " + date);

        // Converting DateTime object into JDK's Calendar.
        Calendar calendar = dateTime.toCalendar(Locale.getDefault());
        System.out.println("java.util.Calendar     = " + calendar);
    }
}

The result of our code snippet:

org.joda.time.DateTime = 2021-10-29T06:54:29.003+08:00
java.util.Date         = Fri Oct 29 06:54:29 CST 2021
java.util.Calendar     = java.util.GregorianCalendar[time=1635461669003,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=9,WEEK_OF_YEAR=44,WEEK_OF_MONTH=5,DAY_OF_MONTH=29,DAY_OF_YEAR=302,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=5,AM_PM=0,HOUR=6,HOUR_OF_DAY=6,MINUTE=54,SECOND=29,MILLISECOND=3,ZONE_OFFSET=28800000,DST_OFFSET=0]

Maven Dependencies

<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.12.5</version>
</dependency>

Maven Central

How do I use Joda-Time’s DateMidnight class?

By Wayan in Joda-Time 0 Comment

The org.joda.time.DateMidnight class represent a date time information with the time value set to midnight. The following snippet show you how to instantiate this class.

package org.kodejava.joda;

import org.joda.time.DateMidnight;
import org.joda.time.format.DateTimeFormat;

public class DateMidnightDemo {
    public static void main(String[] args) {
        // Create DateMidnight object of the current system date.
        DateMidnight date = new DateMidnight();
        System.out.println("date = " + date);

        // Or using the now().
        date = DateMidnight.now();
        System.out.println("date = " + date);

        // Create DateMidnight object by year, month and day.
        date = new DateMidnight(2021, 10, 29);
        System.out.println("date = " + date);

        // Create DateMidnight object from milliseconds.
        date = new DateMidnight(System.currentTimeMillis());
        System.out.println("date = " + date);

        // Parse a date from string.
        date = DateMidnight.parse("2021-10-29");
        System.out.println("date = " + date);

        // Parse a date from string of specified patter.
        date = DateMidnight.parse("29/10/2021", 
                DateTimeFormat.forPattern("dd/MM/yyyy"));
        System.out.println("date = " + date);
    }
}

The result of our code snippet:

date = 2021-10-29T00:00:00.000+08:00
date = 2021-10-29T00:00:00.000+08:00
date = 2021-10-29T00:00:00.000+08:00
date = 2021-10-29T00:00:00.000+08:00
date = 2021-10-29T00:00:00.000+08:00
date = 2021-10-29T00:00:00.000+08:00

Maven Dependencies

<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.12.5</version>
</dependency>

Maven Central

How do I create DateTime object in Joda-Time?

By Wayan in Joda-Time 0 Comment

The following example show you a various way to create an instance of Joda-Time’s DateTime class. By using the default constructor we will create an object with the current system date time. We can also create the object by passing the information like year, month, day, hour, minutes and second.

Joda can also use an instance from JDK’s java.util.Date and java.util.Calendar to create the DateTime. This means that the date object of JDK and Joda can be used to work together in our application.

package org.kodejava.joda;

import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;

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

public class DateTimeDemo {

    public static void main(String[] args) {
        // Creates DateTime object using the default constructor will
        // give you the current system date.
        DateTime date = new DateTime();
        System.out.println("date = " + date);

        // Or simply calling the now() method.
        date = DateTime.now();
        System.out.println("date = " + date);

        // Creates DateTime object with information like year, month,
        // day, hour, minute, second and milliseconds
        date = new DateTime(2021, 10, 29, 0, 0, 0, 0);
        System.out.println("date = " + date);

        // Create DateTime object from milliseconds.
        date = new DateTime(System.currentTimeMillis());
        System.out.println("date = " + date);

        // Create DateTime object from Date object.
        date = new DateTime(new Date());
        System.out.println("date = " + date);

        // Create DateTime object from Calendar object.
        Calendar calendar = Calendar.getInstance();
        date = new DateTime(calendar);
        System.out.println("date = " + date);

        // Create DateTime object from string. The format of the
        // string  should be precise.
        date = new DateTime("2021-10-29T06:30:00.000+08:00");
        System.out.println("date = " + date);
        date = DateTime.parse("2021-10-29");
        System.out.println("date = " + date);
        date = DateTime.parse("29/10/2021",
                DateTimeFormat.forPattern("dd/MM/yyyy"));
        System.out.println("date = " + date);
    }
}

The result of our code snippet:

date = 2021-10-29T06:30:01.068+08:00
date = 2021-10-29T06:30:01.147+08:00
date = 2021-10-29T00:00:00.000+08:00
date = 2021-10-29T06:30:01.148+08:00
date = 2021-10-29T06:30:01.148+08:00
date = 2021-10-29T06:30:01.166+08:00
date = 2021-10-29T06:30:00.000+08:00
date = 2021-10-29T00:00:00.000+08:00
date = 2021-10-29T00:00:00.000+08:00

Maven Dependencies

<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.12.5</version>
</dependency>

Maven Central

How do I create array of unique values from another array?

By Wayan in Core API, Lang Package 2 Comments

This code snippet show you how to create an array of unique numbers from another array of numbers.

package org.kodejava.lang;

import java.util.Arrays;

public class UniqueArray {
    /**
     * Return true if num appeared only once in the array.
     */
    public static boolean isUnique(int[] numbers, int num) {
        for (int number : numbers) {
            if (number == num) {
                return false;
            }
        }
        return true;
    }

    /**
     * Convert the given array to an array with unique values and
     * returns it.
     */
    public static int[] toUniqueArray(int[] numbers) {
        int[] temp = new int[numbers.length];
        // in case you have value of 0 in the array
        Arrays.fill(temp, -1);

        int counter = 0;
        for (int number : numbers) {
            if (isUnique(temp, number))
                temp[counter++] = number;
        }

        int[] uniqueArray = new int[counter];
        System.arraycopy(temp, 0, uniqueArray, 0, uniqueArray.length);
        return uniqueArray;
    }

    /**
     * Print given array
     */
    public static void printArray(int[] numbers) {
        for (int number : numbers) {
            System.out.print(number + " ");
        }
        System.out.println();
    }

    public static void main(String[] args) {
        int[] numbers = {1, 1, 2, 3, 4, 1, 4, 7, 9, 7};
        printArray(numbers);
        printArray(toUniqueArray(numbers));
    }
}

For other example to create unique array check the following example How do I remove duplicate element from array?.

How do I get attributes of element during SAX parsing?

By Wayan in XML 0 Comment

This example show you how to get the attributes of elements in an XML file using the SAX parser.

package org.kodejava.xml;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import java.io.InputStream;

public class SAXElementAttribute {
    public static void main(String[] args) {
        SAXElementAttribute demo = new SAXElementAttribute();
        demo.run();
    }

    private void run() {
        try {
            // Create SAXParserFactory instance and a SAXParser
            SAXParserFactory factory = SAXParserFactory.newInstance();
            SAXParser parser = factory.newSAXParser();

            // Get an InputStream to the elements.xml file and parse
            // its contents using the SAXHandler.
            InputStream is =
                    getClass().getResourceAsStream("/elements.xml");
            DefaultHandler handler = new SAXHandler();
            parser.parse(is, handler);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    static class SAXHandler extends DefaultHandler {
        @Override
        public void startElement(String uri, String localName,
                                 String qName, Attributes attributes)
                throws SAXException {

            int attributeLength = attributes.getLength();
            if ("person".equals(qName)) {
                for (int i = 0; i < attributeLength; i++) {
                    // Get attribute names and values
                    String attrName = attributes.getQName(i);
                    String attrVal = attributes.getValue(i);
                    System.out.print(attrName + " = " + attrVal + "; ");
                }
                System.out.println();
            }
        }
    }
}

The elements.xml file is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <persons>
        <person name="Foo" age="25" />
        <person name="Bar" age="22" />
    </persons>
</root>

How do I build object from XML file using SAX?

By Wayan in XML 0 Comment

This example will show you how to parse an XML file using SAX parser and build an object graph from the parsed XML. We will read the records.xml file that contains some recording information and create the Record object from it.

The DefaultHandler in this example created as an anonymous class. We override some method related to the ContentHandler interface such as the startElement, endElement and characters methods.

package org.kodejava.xml;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;

import org.kodejava.xml.support.Record;

public class SAXDataDemo {
    // List of our records.
    private final List<Record> records = new ArrayList<>();

    // Stacks for storing the elements and objects.
    private final Stack<String> elements = new Stack<>();
    private final Stack<Record> objects = new Stack<>();

    public static void main(String[] args) {
        SAXDataDemo demo = new SAXDataDemo();
        demo.run();
    }

    private void run() {
        try {
            SAXParserFactory factory = SAXParserFactory.newInstance();
            SAXParser parser = factory.newSAXParser();

            String filename = "/records.xml";
            InputStream is = getClass().getResourceAsStream(filename);

            parser.parse(is, new DefaultHandler() {
                @Override
                public void startElement(String uri, String localName, String qName,
                                         Attributes attributes) throws SAXException {
                    elements.push(qName);
                    if ("record".equals(qName)) {
                        Record record = new Record();
                        objects.push(record);
                        records.add(record);
                    }
                }

                @Override
                public void endElement(String uri, String localName,
                                       String qName) throws SAXException {
                    elements.pop();
                }

                @Override
                public void characters(char[] ch, int start, int length)
                        throws SAXException {

                    String value = new String(ch, start, length);
                    if (value.length() == 0) {
                        return;
                    }

                    if ("title".equals(currentElement())) {
                        Record record = objects.peek();
                        record.setTitle(value);
                    } else if ("artist".equals(currentElement())) {
                        Record record = objects.peek();
                        record.setArtist(value);
                    } else if ("genre".equals(currentElement())) {
                        Record record = objects.peek();
                        record.setGenre(value);
                    } else if ("year".equals(currentElement())) {
                        Record record = objects.peek();
                        record.setYear(Integer.parseInt(value));
                    }
                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        }

        for (Record record : records) {
            System.out.println("record = " + record);
        }
    }

    private String currentElement() {
        return elements.peek();
    }
}

The Record class.

package org.kodejava.xml.support;

public class Record {
    private String title;
    private String artist;
    private String genre;
    private int year;

    public Record() {
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public void setArtist(String artist) {
        this.artist = artist;
    }

    public void setGenre(String genre) {
        this.genre = genre;
    }

    public void setYear(int year) {
        this.year = year;
    }

    @Override
    public String toString() {
        return "Record{" +
                "title='" + title + "'\n" +
                ", artist='" + artist + "'\n" +
                ", genre='" + genre + "'\n" +
                ", year=" + year +
                '}';
    }
}

The following XML is the content of our records.xml file.

<?xml version="1.0"?>
<root>
    <records>
        <record>
            <title>Brand New Eyes</title>
            <artist>Paramore</artist>
            <genre>Punk Rock</genre>
            <year>2011</year>
        </record>
        <record>
            <title>Rock Beatles</title>
            <artist>Various Artist</artist>
            <genre>Rock</genre>
            <year>2010</year>
        </record>
    </records>
</root>

When we run this example will get the following output:

record = Record{title='Brand New Eyes'
, artist='Paramore'
, genre='Punk Rock'
, year=2011}
record = Record{title='Rock Beatles'
, artist='Various Artist'
, genre='Rock'
, year=2010}

How do I handle error when parsing an XML file using SAX?

By Wayan in XML 0 Comment

The ErrorHandler interface implemented by the org.xml.sax.helpers.DefaultHandler class provides some methods for error handling mechanism in SAX parsing. The methods are warning(), error(), and fatalError().

package org.kodejava.xml;

import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import java.io.InputStream;

public class SAXErrorHandlerDemo {
    public static void main(String[] args) throws Exception {
        SAXErrorHandlerDemo demo = new SAXErrorHandlerDemo();
        demo.run();
    }

    public void run() throws Exception {
        // Creates the SAXParserFactory and SAXParser instance.
        SAXParserFactory factory = SAXParserFactory.newInstance();
        SAXParser parser = factory.newSAXParser();

        // Parse the error.xml file using MySAXHandler as the 
        // DefaultHandler implementation.
        InputStream is = getClass().getResourceAsStream("/error.xml");
        DefaultHandler handler = new MySAXHandler();
        parser.parse(is, handler);
    }

    // Override the error handling methods defined by the ErrorHandler
    // interface. This method will handler exceptions thrown by the
    // parsing process.
    static class MySAXHandler extends DefaultHandler {
        @Override
        public void warning(SAXParseException e) throws SAXException {
            System.out.println("warning   : " + e.getMessage());
        }

        @Override
        public void error(SAXParseException e) throws SAXException {
            System.out.println("error     : " + e.getMessage());
        }

        @Override
        public void fatalError(SAXParseException e) throws SAXException {
            System.out.println("fatalError: " + e.getMessage());
        }
    }
}