How to find the difference between two LocalDateTime objects?

By Wayan in Java Date Time API 0 Comment

In the previous post, How do I find the difference between two times?, we get the difference between two LocalTime objects in seconds measurement. In this example we will get the difference between two LocalDateTime objects and get the difference between these objects in years, months, days, hours, minutes, seconds and milliseconds.

package org.kodejava.datetime;

import java.time.LocalDateTime;
import java.time.Month;
import java.time.temporal.ChronoUnit;

public class LocalDateTimeDiff {
    public static void main(String[] args) {
        LocalDateTime from = LocalDateTime.of(2021, Month.JANUARY, 10, 10, 0, 30);
        LocalDateTime to = LocalDateTime.now();

        LocalDateTime fromTemp = LocalDateTime.from(from);
        long years = fromTemp.until(to, ChronoUnit.YEARS);
        fromTemp = fromTemp.plusYears(years);

        long months = fromTemp.until(to, ChronoUnit.MONTHS);
        fromTemp = fromTemp.plusMonths(months);

        long days = fromTemp.until(to, ChronoUnit.DAYS);
        fromTemp = fromTemp.plusDays(days);

        long hours = fromTemp.until(to, ChronoUnit.HOURS);
        fromTemp = fromTemp.plusHours(hours);

        long minutes = fromTemp.until(to, ChronoUnit.MINUTES);
        fromTemp = fromTemp.plusMinutes(minutes);

        long seconds = fromTemp.until(to, ChronoUnit.SECONDS);
        fromTemp = fromTemp.plusSeconds(seconds);

        long millis = fromTemp.until(to, ChronoUnit.MILLIS);

        System.out.println("From = " + from);
        System.out.println("To   = " + to);
        System.out.printf("The difference is %s years, %s months, %s days, " +
                        "%s hours, %s minutes, %s seconds, %s millis",
                years, months, days, hours, minutes, seconds, millis);
    }
}

The result of the code snippet above when executed is:

From = 2021-01-10T10:00:30
To   = 2021-11-17T15:07:37.913247900
The difference is 0 years, 10 months, 7 days, 5 hours, 7 minutes, 7 seconds, 913 millis

How do I find the difference between two times?

By Wayan in Java Date Time API 0 Comment

The following code snippet show you how to find the difference between two time objects represented by LocalTime class. To get the difference between two LocalTime objects we can use the Duration.between() method. This method returns a Duration object, to get the difference in seconds we call the getSeconds() method.

Here a code snippet to demonstrate it.

package org.kodejava.datetime;

import java.time.*;

public class TimeDifference {
    public static void main(String[] args) {
        LocalTime start = LocalTime.now();
        LocalTime end = LocalTime.of(16, 59, 55);
        Duration duration = Duration.between(start, end);

        System.out.printf("Seconds between %s and %s is: %s seconds.%n",
                start, end, duration.getSeconds());

        diffLocalDateTime();
        diffInstant();
    }

    /**
     * Difference between two LocalDateTime objects.
     */
    public static void diffLocalDateTime() {
        LocalDateTime dt1 = LocalDateTime.now();
        LocalDateTime dt2 = LocalDateTime.now(ZoneId.of("GMT+0"));
        Duration duration = Duration.between(dt1, dt2);
        System.out.printf("Duration = %s seconds.%n", duration.getSeconds());
    }

    /**
     * Difference between two Instant objects.
     */
    public static void diffInstant() {
        Instant instant1 = Instant.now();
        Instant instant2 = Instant.EPOCH;
        Duration duration = Duration.between(instant1, instant2);
        System.out.printf("Duration = %s seconds.%n", duration.getSeconds());
    }
}

Using the Duration.between() we can also get the difference between two LocalDateTime objects and two Instant object as seen in the diffLocalDateTime() method and diffInstant method in the code snippet above.

The result of the code snippet:

Seconds between 15:05:35.401317900 and 16:59:55 is: 6859 seconds.
Duration = -28800 seconds.
Duration = -1637132736 seconds.

How do I specify the Java compiler version in a pom.xml file?

By Wayan in Maven, Tools 0 Comment

When you need to compile a project for a specific Java version you can configure maven compiler plugin to set the source and the target version. The following pom.xml file configuration show you how to do it.

<project>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.2</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Invalid value for the source and the target version in our project will make our project compilation process failed. For example when we try to use the diamond operator (<>) which available in Java 7, while the maven compiler plugin is set to version 1.5, can produce compiler error like this:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project servlet-example: Compilation failure
[ERROR] /Users/wsaryada/Studio/kodejava.org/webapp-example/servlet-example/src/main/java/org/kodejava/example/servlet/SessionCounter.java:[10,51] diamond operator is not supported in -source 1.5
[ERROR] (use -source 7 or higher to enable diamond operator)

How do I parse negative number in parentheses?

By Wayan in Core API, Text Package 0 Comment

In financial application negative numbers are often represented in parentheses. In this post we will learn how we can parse or convert the negative number in parentheses to produce the represented number value. To parse text / string to a number we can use the java.text.DecimalFormat class.

Beside number in parentheses, in this example we also parse negative number that use the minus sign with the currency symbol like $. Let’s jump to the code snippet below:

package org.kodejava.text;

import java.text.DecimalFormat;

public class NegativeNumberParse {
    // Pattern for parsing negative number.
    public static final String PATTERN1 = "#,##0.00;(#,##0.00)";
    public static final String PATTERN2 = "$#,##0.00;-$#,##0.00";

    public static void main(String[] args) throws Exception {
        DecimalFormat df = new DecimalFormat(PATTERN1);

        String number1 = "(1000)";
        String number2 = "(1,500.99)";

        System.out.println("number1 = " + df.parse(number1));
        System.out.println("number2 = " + df.parse(number2));

        df = (DecimalFormat) DecimalFormat.getInstance();
        df.applyPattern(PATTERN2);

        String number3 = "-$1000";
        String number4 = "-$1,500.99";

        System.out.println("number3 = " + df.parse(number3));
        System.out.println("number4 = " + df.parse(number4));
    }
}

And here are the results of our code snippet above:

number1 = -1000
number2 = -1500.99
number3 = -1000
number4 = -1500.99

If you need to display or format negative numbers in parentheses you can take a look at the following example How do I display negative number in parentheses?.

Why do I get NotOLE2FileException: Invalid header signature error?

By Wayan in Apache POI 2 Comments

When I was creating the code snippet for the How do I replace text in Microsoft Word document using Apache POI? I got the following error when running the snippet . As additional information, the code snippet for the Kodejava website is written as a Maven project.

org.apache.poi.poifs.filesystem.NotOLE2FileException: Invalid header signature; read 0xE011BDBFEFBDBFEF, expected 0xE11AB1A1E011CFD0 – Your file appears not to be a valid OLE2 document

This error message was produce when the code trying to open a Word document. The Apache POI reports that the Word document has an invalid header signature, not a valid OLE2 document. Comparing the original document with the document under maven’s target directory I found out that the file size was different. This could mean that something alter the document and corrupt the header.

After doing some googling, I found out that this error is due to maven resource filtering. The maven resource filtering process cause the Word document header corrupt during the copy phase. The solution to this problem is to make sure that the filtering process is set to false. The pom.xml of the maven project should be altered to have the following configuration.

<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <filtering>false</filtering>
        </resource>
    </resources>
</build>