How do I get the available font family names?

By Wayan in AWT, Core API 0 Comment 
package org.kodejava.awt;

import java.awt.GraphicsEnvironment;

public class FontFamilyNameList {
    public static void main(String[] args) {
        // Get all available font family names from GraphicsEnvironment
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        String[] familyNames = ge.getAvailableFontFamilyNames();

        // Iterates familyNames array to display the available font's family names
        for (String familyName : familyNames) {
            System.out.println("Family name: " + familyName);
        }
    }
}

Some font family names are shown below:

Family name: Agency FB
Family name: Algerian
Family name: Arial
Family name: Arial Black
Family name: Arial Narrow
Family name: Arial Rounded MT Bold
Family name: Bahnschrift
Family name: Baskerville Old Face
Family name: Bauhaus 93
Family name: Bell MT
...

How do I get the available font names?

By Wayan in AWT, Core API 0 Comment 
package org.kodejava.awt;

import java.awt.Font;
import java.awt.GraphicsEnvironment;

public class FontNameList {
    public static void main(String[] args) {
        // Get all available fonts from GraphicsEnvironment
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        Font[] fonts = ge.getAllFonts();

        // Iterates all available fonts and get their name and family name
        for (Font font : fonts) {
            String fontName = font.getName();
            String familyName = font.getFamily();

            System.out.println("Font: " + fontName + "; family: " + familyName);
        }
    }
}

Here are some fonts name printed from the code snippet above:

Font: Agency FB; family: Agency FB
Font: Agency FB Bold; family: Agency FB
Font: Algerian; family: Algerian
Font: Arial; family: Arial
Font: Arial Black; family: Arial Black
Font: Arial Bold; family: Arial
Font: Arial Bold Italic; family: Arial
Font: Arial Italic; family: Arial
Font: Arial Narrow; family: Arial Narrow
Font: Arial Narrow Bold; family: Arial Narrow
...

How do I parse a number for a locale?

By Wayan in Core API, Text Package 0 Comment 
package org.kodejava.text;

import java.util.Locale;
import java.text.NumberFormat;
import java.text.ParseException;

public class LocaleNumberParse {
    public static void main(String[] args) {
        try {
            // In this example we are trying to parse a number string in a
            // defined format. Basically we want to covert the string for a
            // locale into a correct number value.
            Number number =
                NumberFormat.getNumberInstance(Locale.JAPAN).parse("25,000.75");

            // Just do some stuff with the number from the parse process
            if (number instanceof Long) {
                System.out.println("This number is instanceof Long and the " +
                    "value is: " + number.longValue());
            } else if (number instanceof Double) {
                System.out.println("This number is instanceof Double and the " +
                    "value is: " + number.doubleValue());
            }
        } catch (ParseException e) {
            e.printStackTrace();
        }

    }
}

The code snippet print out the following result:

This number is instanceof Double and the value is: 25000.75

How do I format a number for a locale?

By Wayan in Core API, Text Package 0 Comment 
package org.kodejava.text;

import java.util.Locale;
import java.text.NumberFormat;

public class LocaleNumberFormat {
    public static void main(String[] args)  {
        // Format number for Italy locale. In Italy locale the decimal point
        // symbol is a comma.
        NumberFormat formatter = NumberFormat.getNumberInstance(Locale.ITALY);
        try {
            String number = formatter.format(195325.75);
            System.out.println("Number in Italy: " + number);
        } catch (NumberFormatException e) {
            e.printStackTrace();
        }

        // Format number for Japan locale. In Japan locale the decimal point
        // symbol is a dot.
        formatter = NumberFormat.getNumberInstance(Locale.JAPAN);
        try {
            String number = formatter.format(195325.75);
            System.out.println("Number in Japan: " + number);
        } catch (NumberFormatException e) {
            e.printStackTrace();
        }
    }
}

The code snippet output:

Number in Italy: 195.325,75
Number in Japan: 195,325.75

How do I iterate a subset of a string?

By Wayan in Core API, Text Package 0 Comment 
package org.kodejava.text;

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

public class IterateSubstringExample {
    private static final String text =
        "How razorback-jumping frogs can level six piqued gymnasts";

    public static void main(String[] args) {
        CharacterIterator it = new StringCharacterIterator(text, 4, 27, 5);

        // In this loop we just iterator a subset of character defined in the
        // StringCharacterIterator above. It reads from the 4 index of the
        // string up to the 27 character. So it will just take the following
        // string "razorback-jumping frogs"
        for (char ch = it.first(); ch != CharacterIterator.DONE; ch = it.next()) {
            System.out.print(ch);
        }
    }
}

The output of the code snippet above will be:

razorback-jumping frogs

How do I reverse a string using CharacterIterator?

By Wayan in Core API, Text Package 0 Comment

In this example we use the java.text.CharacterIterator implementation class java.text.StringCharacterIterator to reverse a string. It’s done by reading a string from the last index up to the beginning of the string.

package org.kodejava.text;

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

public class StringCharacterIteratorReverseExample {
    private static final String text = "Jackdaws love my big sphinx of quartz";

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

        System.out.println("Before = " + text);
        System.out.print("After  = ");
        // Iterates a string from the last index to the beginning.
        for (char ch = it.last(); ch != CharacterIterator.DONE; ch = it.previous()) {
            System.out.print(ch);
        }
    }
}

The result of the code snippet above:

Before = Jackdaws love my big sphinx of quartz
After  = ztrauq fo xnihps gib ym evol swadkcaJ

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 disable auto-commit mode in JDBC?

By Wayan in JDBC 0 Comment

The code snippet below shows you how to disable auto-commit operation when executing JDBC commands or queries.

package org.kodejava.jdbc;

import java.sql.*;

public class AutoCommitSettingExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        // DO: Get a connection to database, we need to obtain the
        // database connection prior to executing any JDBC commands
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Disable the auto-commit operation. By default, every statement
            // executed against database in JDBC is in auto-commit mode. To
            // disable auto-commit set it to false
            connection.setAutoCommit(false);

            // DO: Execute some other database operation here
            String sql = "DELETE FROM book WHERE id = ?";
            try (PreparedStatement statement = connection.prepareStatement(sql)) {
                statement.setLong(1, 1L);
                statement.executeUpdate();

                // Finally we must call the commit method explicitly to finish
                // all database manipulation operation
                connection.commit();
            } catch (SQLException e) {
                // When some exception occurs rollback the transaction.
                connection.rollback();
                throw e;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central

How do I read text file in Servlet?

By Wayan in Servlet 5 Comments

This example show you how to read a text file in a servlet. Using the ServletContext.getResourceAsStream() method will enable you to read a file whether the web application is deployed in an exploded format or in a war file archive.

The following servlet read the configuration.properties file from the /WEB-INF directory in our web application. The configuration.properties file is just a regular text file with the following contents.

app.appname=Servlet Examples
app.version=1.0
app.copyright=2021

Here is our ReadTextFileServlet servlet class.

package org.kodejava.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;

@WebServlet(name = "ReadTextFileServlet", urlPatterns = "/read-text-file")
public class ReadTextFileServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request,
                         HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html");

        // We are going to read a file called configuration.properties. This
        // file is placed under the WEB-INF directory.
        String filename = "/WEB-INF/configuration.properties";

        ServletContext context = getServletContext();

        // First get the file InputStream using ServletContext.getResourceAsStream()
        // method.
        InputStream is = context.getResourceAsStream(filename);
        if (is != null) {
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader reader = new BufferedReader(isr);
            PrintWriter writer = response.getWriter();
            String text;

            // We read the file line by line and later will be displayed on the
            // browser page.
            while ((text = reader.readLine()) != null) {
                writer.println(text + "</br>");
            }
        }
    }
}

To access the servlet you can type http://localhost:8080/read-text-file in your browser URL address bar.

Maven dependencies

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
</dependency>

Maven Central

How do I create a scheduled task using timer?

By Wayan in Core API, Util Package 0 Comment

This example show you how to create a simple class for scheduling a task using Timer and TimerTask class.

package org.kodejava.util;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

public class TimerExample extends TimerTask {
    private final DateFormat formatter = new SimpleDateFormat("hh:mm:ss a");

    public static void main(String[] args) {
        // Create an instance of TimerTask implementor.
        TimerTask task = new TimerExample();

        // Create a new timer to schedule the TimerExample instance at a
        // periodic time every 5000 milliseconds (5 seconds) and start it
        // immediately
        Timer timer = new Timer();
        timer.scheduleAtFixedRate(task, new Date(), 5000);
    }

    /**
     * This method is the implementation of a contract defined in the 
     * TimerTask class. This in the entry point of the task execution.
     */
    public void run() {
        // To make the example simple we just print the current time.
        System.out.println(formatter.format(new Date()));
    }
}

Here is the result printed by the code snippet above:

09:53:28 AM
09:53:33 AM
09:53:38 AM
09:53:43 AM
09:53:48 AM