Using format flags to format negative number in parentheses

In this example we are going to learn to use a java.util.Formatter to format negative number in parentheses. The Formatter can use a format flags to format a value. To display a negative number in parentheses we can use the ( flag. This flag display negative number inside parentheses instead of using the - symbol.

The following code snippet below will show you how to do it. We start the example by using the Formatter object and simplified using the format() method of the String class.

package org.kodejava.util;

import java.util.Formatter;
import java.util.Locale;

public class FormatNegativeNumber {
    public static void main(String[] args) {
        // Creates an instance of Formatter, format the number using the
        // format and print out the result.
        Formatter formatter = new Formatter();
        formatter.format("%(,.2f", -199.99f);
        System.out.println("number1 = " + formatter);

        // Use String.format() method instead of creating an instance of
        // Formatter. Format a negative number using Germany locale.
        String number2 = String.format(Locale.GERMANY, "%(,8.2f", -49.99);
        System.out.println("number2 = " + number2);

        // Format number using Indonesian locale. The thousand separator is "."
        // in Indonesian number.
        String number3 = String.format(new Locale("id", "ID"), "%(,d", -10000);
        System.out.println("number3 = " + number3);
    }
}

The result of this code snippet:

number1 = (199.99)
number2 =  (49,99)
number3 = (10.000)

How do I manipulate LocalDate object using TemporalAdjuster?

In the previous example we manipulate the value of LocalDate by adding or subtracting the value of date object by days, months, years using methods like plusMonths() or minusDays(). Or by changing the year or the month of the date object using methods like withYear() or withMonth().

But there are times that we want to manipulate the date object so that we can get the first day of the month or the last day of the month. We want to manipulate the date value to advance the date to the first Monday after the current day or the last the of the year.

To manipulate the date object in this way we can use the with() method and pass a TemporalAdjuster object as an argument. Fortunately, the Date and Time API already provide some commonly used TemporalAdjuster. These TemporalAdjuster are provided as a static factory methods that we can find in the java.time.temporal.TemporalAdjusters class.

The following example is a code snippet to manipulate the date object using TemporalAdjuster / TemporalAdjusters class.

package org.kodejava.datetime;

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;

public class DateManipulationWithTemporalAdjuster {
    public static void main(String[] args) {
        LocalDate date = LocalDate.now();
        System.out.println("Current date       = " + date);

        LocalDate date1 = date.with(TemporalAdjusters.firstDayOfMonth());
        System.out.println("First day of month = " + date1);

        LocalDate date2 = date.with(TemporalAdjusters.lastDayOfMonth());
        System.out.println("Last day of month  = " + date2);

        LocalDate date3 = date.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
        System.out.println("Next Monday        = " + date3);

        LocalDate date4 = date.with(TemporalAdjusters.lastDayOfYear());
        System.out.println("Last day of year   = " + date4);
    }
}

The result of the code snippet are:

Current date       = 2021-11-18
First day of month = 2021-11-01
Last day of month  = 2021-11-30
Next Monday        = 2021-11-22
Last day of year   = 2021-12-31

The table below shows the complete static factory methods provided by the TemporalAdjusters class.

Method Name Method Description
dayOfWeekInMonth Returns a new date in the same month with the ordinal day-of-week.
firstDayOfMonth Returns a new date set to the first day of the current month.
firstDayOfNextMonth Returns a new date set to the first day of the next month.
firstDayOfNextYear Returns a new date set to the first day of the next year.
firstDayOfYear Returns a new date set to the first day of the current year.
firstInMonth Returns a new date in the same month with the first matching day-of-week.
lastDayOfMonth Returns a new date set to the last day of the current month.
lastDayOfYear Returns a new date set to the last day of the current year.
lastInMonth Returns a new date in the same month with the last matching day-of-week.
next Returns the next day-of-week adjuster.
nextOrSame Returns the next-or-same day-of-week adjuster.
ofDateAdjuster Returns user-written adjuster.
previous Returns the previous day-of-week adjuster.
previousOrSame Returns the previous-or-same day-of-week adjuster.

How do I install third-party libraries in Maven repository?

Sometimes when the required libraries / dependencies is not available in the Maven Central Repository we need to manually install it to our local repository. This library must be placed in the correct directory in our local repository to enable Maven to find it. The default location is under the ${user.home}/.m2/repository.

To make this job easier Maven provides a maven-install-plugin that will help us to install the third-party library in the correct place. The following command shows how to do it.

The long command

mvn install:install-file -Dfile=<path-to-file> -DgroupId=<group-id> \
        -DartifactId=<artifact-id> -Dversion=<version> -Dpackaging=<packaging>

Where:

  • -Dfile = path to the third-party library file
  • -DgroupId = the groupId of the library
  • -DartifactId = the artifactId of the library
  • -Dversion = the version number of the library
  • -Dpackaging = the library packaging

An example to install an Oracle JDBC library to your local repository is:

mvn install:install-file -Dfile=ojdbc7.jar -DgroupId=com.oracle \
        -DartifactId=ojdbc7 -Dversion=12.1.0.2 -Dpackaging=jar

The simple command

If you have the pom.xml file, you can install it with the following command:

mvn install:install-file \
        -Dfile=<path-to-file> \
        -DpomFile=<path-to-pomfile>

Where:

  • -Dfile = path to the third-party library file
  • -DpomFile = the location to the library pom.xml file

Starting with the Maven version 2.5 you can use even a simpler command. When the library is build by Maven, a pom.xml file will be placed under the META-INF directory. This pom.xml file will be used by default when we install the library. To install a library all you need is the following command:

mvn install:install-file -Dfile=<path-to-file>

How do I manipulate the value of LocalDate object?

In the following example we will learn how to manipulate a LocalDate object. There are many methods available for us to change the value of a LocalDate object. For example, we can change the year, month and day of LocalDate object. We can use methods like withYear(), withDayOfMonth(), plusYears(), minusMonths(), etc. All these methods will return a new LocalDate object, the original LocalDate will stay unchanged.

Let’s see the following code example for demonstration on how to manipulate the value of LocalDate object.

package org.kodejava.datetime;

import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.ChronoField;
import java.time.temporal.ChronoUnit;

public class LocalDateManipulation {
    public static void main(String[] args) {
        absoluteAttributeManipulations();
        relativeAttributeManipulations();
    }

    private static void absoluteAttributeManipulations() {
        System.out.println("LocalDateManipulation.absoluteAttributeManipulations");
        LocalDate date1 = LocalDate.of(2021, Month.JANUARY, 1);
        LocalDate date2 = date1.withYear(2010);
        LocalDate date3 = date2.withMonth(Month.DECEMBER.getValue());
        LocalDate date4 = date3.withDayOfMonth(15);
        LocalDate date5 = date4.with(ChronoField.DAY_OF_YEAR, 100);

        System.out.println("of(2021, Month.JANUARY, 1)                 => " + date1);
        System.out.println("date1.withYear(2010)                       => " + date2);
        System.out.println("date2.withMonth(Month.DECEMBER.getValue()) => " + date3);
        System.out.println("date3.withDayOfMonth(15)                   => " + date4);
        System.out.println("date4.with(ChronoField.DAY_OF_YEAR, 100)   => " + date5);
    }

    private static void relativeAttributeManipulations() {
        System.out.println("LocalDateManipulation.relativeAttributeManipulations");
        LocalDate date1 = LocalDate.of(2021, Month.AUGUST, 17);
        LocalDate date2 = date1.minusYears(70);
        LocalDate date3 = date2.plusMonths(10);
        LocalDate date4 = date3.minusDays(15);
        LocalDate date5 = date4.plusWeeks(52);
        LocalDate date6 = date5.minus(52, ChronoUnit.WEEKS);

        System.out.println("of(2021, Month.AUGUST, 17)        => " + date1);
        System.out.println("date1.minusYears(70)              => " + date2);
        System.out.println("date1.plusMonths(10)              => " + date3);
        System.out.println("date3.minusDays(15)               => " + date4);
        System.out.println("date4.plusWeeks(52)               => " + date5);
        System.out.println("date5.minus(52, ChronoUnit.WEEKS) => " + date6);

    }
}

The results of this code snippet are:

LocalDateManipulation.absoluteAttributeManipulations
of(2021, Month.JANUARY, 1)                 => 2021-01-01
date1.withYear(2010)                       => 2010-01-01
date2.withMonth(Month.DECEMBER.getValue()) => 2010-12-01
date3.withDayOfMonth(15)                   => 2010-12-15
date4.with(ChronoField.DAY_OF_YEAR, 100)   => 2010-04-10

LocalDateManipulation.relativeAttributeManipulations
of(2021, Month.AUGUST, 17)        => 2021-08-17
date1.minusYears(70)              => 1951-08-17
date1.plusMonths(10)              => 1952-06-17
date3.minusDays(15)               => 1952-06-02
date4.plusWeeks(52)               => 1953-06-01
date5.minus(52, ChronoUnit.WEEKS) => 1952-06-02

How do I run FTP server in Mac OS X?

I need to test FTP client codes, so I need to find an FTP server for testing my codes. After searching for a while I find out that OS X already equipped FTP server. I am currently using OS X El Capitan 10.11.*.

Let’s now test the FTP server on Mac OS X with the following steps:

  • Launch the Terminal.app
  • Type the following command to start the FTP server.
sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist
  • Connect to the FTP server by running ftp localhost command.
  • We’ll be asked to enter the username and password.
$ ftp localhost
Trying ::1...
Connected to localhost.
220 ::1 FTP server (tnftpd 20100324+GSSAPI) ready.
Name (localhost:wsaryada): wsaryada
331 User wsaryada accepted, provide password.
Password: 
230 User wsaryada logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp>
  • If we see the messages above and the ftp> prompt means that the FTP server works and ready to accept our command.
  • We can also try to access the FTP server using a browser. In the URL box type `ftp://localhost` to connect. We need to supply username and password to login.
  • To exit or close the connection to FTP server we can run the exit command.
  • Finally, to shut down the FTP server we run:
sudo -s launchctl unload -w /System/Library/LaunchDaemons/ftp.plist

After the FTP server ready, I can now continue to create some test program to access the FTP server. There are already some examples you can find in the Apache Commons Net category that use the FTPClient library to access FTP server.