How do I iterate each character of a string?

By Wayan in Core API, Text Package 0 Comment

The following example show you how to iterate each character of a string using the java.text.CharacterIterator and java.text.StringCharacterIterator to count the number of vowels and consonants in the string.

package org.kodejava.text;

import java.text.CharacterIterator;
import java.text.StringCharacterIterator;

public class StringCharacterIteratorExample {
    private static final String text =
        "The quick brown fox jumps over the lazy dog";

    public static void main(String[] args) {
        CharacterIterator it = new StringCharacterIterator(text);

        int vowels = 0;
        int consonants = 0;

        // Iterates character sets from the beginning to the last character
        for (char ch = it.first(); ch != CharacterIterator.DONE; ch = it.next()) {
            if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
                vowels = vowels + 1;
            } else if (ch != ' ') {
                consonants = consonants + 1;
            }
        }

        System.out.println("Number of vowels: " + vowels);
        System.out.println("Number of consonants: " + consonants);
    }
}

The output of the code snippet above:

Number of vowels: 11
Number of consonants: 24

How do I format a date-time value?

By Wayan in Core API, Text Package 0 Comment

In the DateFormat class there are some predefined constants that we can use to format a date time value. Here is an example of it.

package org.kodejava.text;

import java.text.DateFormat;
import java.util.Date;

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

        // Format date in a short format
        String today = DateFormat.getDateTimeInstance(DateFormat.SHORT,
                DateFormat.SHORT).format(date);
        System.out.println("Today " + today);

        // Format date in a medium format
        today = DateFormat.getDateTimeInstance(DateFormat.MEDIUM,
                DateFormat.MEDIUM).format(date);
        System.out.println("Today " + today);

        // Format date in a long format
        today = DateFormat.getDateTimeInstance(DateFormat.LONG,
                DateFormat.LONG).format(date);
        System.out.println("Today " + today);
    }
}

And you’ll see the result as follows:

Today 9/24/21 9:40 AM
Today Sep 24, 2021 9:40:28 AM
Today September 24, 2021 9:40:28 AM CST

How do I format a date into dd/MM/yyyy?

By Wayan in Core API, Text Package 11 Comments

Formatting how data should be displayed on the screen is a common requirement when creating a program or application. Displaying information in a good and concise format can be an added values to the users of the application. In the following code snippet we will learn how to format a date into a certain display format.

For these purposes we can utilize the DateFormat and SimpleDateFormat classes from the java.text package. We can easily format a date in our program by creating an instance of SimpleDateFormat class and specify to format pattern. Calling the DateFormat.format(Date date) method will format a date into a date-time string.

You can see the details about date and time patters in the following link: Date and Time Patterns. Now, let’s see an example as shown in the code snippet below.

package org.kodejava.text;

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

public class DateFormatExample {
    public static void main(String[] args) {
        Date date = Calendar.getInstance().getTime();

        // Display a date in day, month, year format
        DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
        String today = formatter.format(date);
        System.out.println("Today : " + today);

        // Display date with day name in a short format
        formatter = new SimpleDateFormat("EEE, dd/MM/yyyy");
        today = formatter.format(date);
        System.out.println("Today : " + today);

        // Display date with a short day and month name
        formatter = new SimpleDateFormat("EEE, dd MMM yyyy");
        today = formatter.format(date);
        System.out.println("Today : " + today);

        // Formatting date with full day and month name and show time up to
        // milliseconds with AM/PM
        formatter = new SimpleDateFormat("EEEE, dd MMMM yyyy, hh:mm:ss.SSS a");
        today = formatter.format(date);
        System.out.println("Today : " + today);
    }
}

Let’s view what we got on the console:

Today : 24/09/2021
Today : Fri, 24/09/2021
Today : Fri, 24 Sep 2021
Today : Friday, 24 September 2021, 09:36:32.724 AM

How do I format a number?

By Wayan in Core API, Text Package 0 Comment

If you want to display some numbers that is formatted to a certain pattern, either in a Java Swing application or in a JSP file, you can utilize NumberFormat and DecimalFormat class to give you the format that you want. Here is a small example that will show you how to do it.

In the code snippet below we start by creating a double variable that contains some value. By default, the toString() method of the double data type will print the money value using a scientific number format as it is greater than 10^7 (10,000,000.00). To be able to display the number without scientific number format we can use java.text.DecimalFormat which is a sub class of java.text.NumberFormat.

We create a formatter using DecimalFormat class with a pattern of #0.00. The # symbol means any number but leading zero will not be displayed. The 0 symbol will display the remaining digit and will display as zero if no digit is available.

package org.kodejava.text;

import java.text.DecimalFormat;
import java.text.NumberFormat;

public class DecimalFormatExample {
    public static void main(String[] args) {
        // We have some millions money here that we'll format its look.
        double money = 100550000.75;

        // Creates a formatter
        NumberFormat formatter = new DecimalFormat("#0.00");

        // Print the number using scientific number format and using our 
        // defined decimal format pattern above.
        System.out.println(money);
        System.out.println(formatter.format(money));
    }
}

Here is the different result of the code above.

1.0055000075E8
100550000.75

How do I convert Date to String?

By Wayan in Core API, Text Package 1 Comment 
package org.kodejava.text;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;
import java.util.Date;

public class DateToString {
    public static void main(String[] args) {
        // Create an instance of SimpleDateFormat used for formatting
        // the string representation of date (day/month/year)
        String pattern = "dd/MM/yyyy";
        DateFormat df = new SimpleDateFormat(pattern);

        // Get the date today using Calendar object.
        Date today = Calendar.getInstance().getTime();

        // Using DateFormat format method we can create a string
        // representation of a date with the defined format.
        String reportDate = df.format(today);

        // Print what date is today!
        System.out.println("Report Date: " + reportDate);

        // Using Java 8.
        // Creates a DateTimeFormatter using the ofPattern() method. Get
        // the current date by calling the .now() method of LocalDate.
        // To convert to string use the format() method of the LocalDate
        // and pass the formatter object as argument.
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
        LocalDate now = LocalDate.now();
        reportDate = now.format(formatter);
        System.out.println("Report Date: " + reportDate);
    }
}

How do I get a list of weekday names?

By Wayan in Core API, Text Package 0 Comment

The example code below helps you to get all weekday names as an array of string. The first method, getWeekdays() return the full name string while the second method getShortWeekdays() return the short name of the weekday.

package org.kodejava.text;

import java.text.DateFormatSymbols;

public class WeekdayNames {
    public static void main(String[] args) {
        DateFormatSymbols dfs = new DateFormatSymbols();

        String[] weekdays = dfs.getWeekdays();
        for (String weekday : weekdays) {
            System.out.println("weekday = " + weekday);
        }

        String[] shortWeekdays = dfs.getShortWeekdays();
        for (String shortWeekday : shortWeekdays) {
            System.out.println("shortWeekday = " + shortWeekday);
        }
    }
}

The results of the code above are:

weekday = 
weekday = Sunday
weekday = Monday
weekday = Tuesday
weekday = Wednesday
weekday = Thursday
weekday = Friday
weekday = Saturday
shortWeekday = 
shortWeekday = Sun
shortWeekday = Mon
shortWeekday = Tue
shortWeekday = Wed
shortWeekday = Thu
shortWeekday = Fri
shortWeekday = Sat

How do I get a list of month names?

By Wayan in Core API, Text Package 6 Comments

The example code below helps you to get all month names as an array of String. The first method, getMonths() return the full name string while the second method getShortMonths() return the short name of the month.

package org.kodejava.text;

import java.text.DateFormatSymbols;
import java.util.Locale;

public class MonthNames {
    public static void main(String[] args) {
        String[] months = new DateFormatSymbols().getMonths();
        for (String month : months) {
            System.out.println("month = " + month);
        }

        String[] shortMonths = new DateFormatSymbols().getShortMonths();
        for (String shortMonth : shortMonths) {
            System.out.println("shortMonth = " + shortMonth);
        }

        DateFormatSymbols dfs = new DateFormatSymbols(Locale.GERMANY);
        String[] germanyMonths = dfs.getMonths();
        for (String germanyMonth : germanyMonths) {
            System.out.println("germanyMonth = " + germanyMonth);
        }

        String[] germanyShortMonths = dfs.getShortMonths();
        for (String germanyShortMonth : germanyShortMonths) {
            System.out.println("germanyShortMonth = "
                    + germanyShortMonth);
        }
    }
}

The results of the code above are:

month = January
month = February
...
month = December
month = 
shortMonth = Jan
shortMonth = Feb
...
shortMonth = Dec
shortMonth = 
germanyMonth = Januar
germanyMonth = Februar
...
germanyMonth = Dezember
germanyMonth = 
germanyShortMonth = Jan
germanyShortMonth = Feb
...
germanyShortMonth = Dez
germanyShortMonth =

How do I convert String into Date Object in Java?

By Wayan in Core API, Text Package 0 Comment

The following code shows how we can convert a string representation of date into java.util.Date object.

To convert a string of date we can use the help from java.text.SimpleDateFormat that extends java.text.DateFormat abstract class.

package org.kodejava.text;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Date;

public class ConvertStringToDateExample {
    public static void main(String[] args) {
        String pattern = "dd/MM/yyyy";
        String date = "15/09/2021";

        try {
            DateFormat df = new SimpleDateFormat(pattern);
            Date today = df.parse(date);
            System.out.println("Today = " + df.format(today));
        } catch (ParseException e) {
            e.printStackTrace();
        }

        // Using Java 8 Date and Time
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
        LocalDate localDate = LocalDate.parse(date, formatter);
        System.out.println("Today = " + localDate.format(formatter));
    }
}

And here is the result of our code:

Today = 15/09/2021
Today = 15/09/2021

The example starts by creating an instance of SimpleDateFormat with dd/MM/yyyy format which mean that the date string is formatted in day-month-year sequence.

Finally, using the parse(String source) method we can get the Date instance. Because parse method can throw java.text.ParseException exception if the supplied date is not in a valid format; we need to catch it.

Here are the list of defined patterns that can be used to format the date taken from the Java class documentation.

Letter Date / Time Component Examples
G Era designator AD
y Year 1996; 96
M Month in year July; Jul; 07
w Week in year 27
W Week in month 2
D Day in year 189
d Day in month 10
F Day of week in month 2
E Day in week Tuesday; Tue
a Am/pm marker PM
H Hour in day (0-23) 0
k Hour in day (1-24) 24
K Hour in am/pm (0-11) 0
h Hour in am/pm (1-12) 12
m Minute in hour 30
s Second in minute 55
S Millisecond 978
z Time zone Pacific Standard Time; PST; GMT-08:00
Z Time zone -0800