How do I create MySQL database programmatically in Java?

There are times that you might need to create a database or tables right after you run your program instead of manually creating it. In this example, I will show you how you can do this using JDBC and MySQL database. The first thing we need to do as usual when creating a JDBC program is to define a JDBC URL. One thing that you’ll notice here is that we don’t define the database name in the URL. So the URL will be like jdbc:mysql://localhost.

After defining the URL, we need to create a connection to the database. We issued the DriverManager.getConnection() method and pass the URL, username and password as the arguments. The next step is to create a PreparedStatement. When we call the preparedStatement() method we pass an SQL command to create the database, which is CREATE DATABASE IF NOT EXISTS demodb. This will create a new database if there is no database with demodb name exists in the database. Finally, call the PreparedStatement‘s execute() method

Now you can try for your self, start typing the following code snippet in your text editor or IDE, and execute it to create the database.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

public class CreateMySQLDatabaseExample {
    public static void main(String[] args) {
        // Defines the JDBC URL. As you can see, we are not specifying
        // the database name in the URL.
        String url = "jdbc:mysql://localhost";

        // Defines username and password to connect to database server.
        String username = "root";
        String password = "root";

        // SQL command to create a database in MySQL.
        String sql = "CREATE DATABASE IF NOT EXISTS demodb";

        try (Connection conn = DriverManager.getConnection(url, username, password);
             PreparedStatement stmt = conn.prepareStatement(sql)) {

            stmt.execute();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

After you are executing the code snippet above you will find a new database named demodb created in your MySQL database server.

Maven Dependencies

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

Maven Central

How do I set up JAVA_HOME and Path variables in Windows?

Setting up a JAVA_HOME and Path variables is the second thing you’ll need to do after installing a JDK (Java Development Kit). Although this is not required by Java itself, it is commonly use by other application. For instance then Apache Tomcat web application server and other application server will need it. Or we might need it if we want to compile or running our Java classes from the command prompt. It helps us to organize the default JDK and the execution path.

So here are the steps that we’ll need to do to configure the JAVA_HOME and Path variable on a Windows operating system.

Step 1. Finding the location of our JDK installation directory. If we already know where we have installed the JDK continue to the Step 2.

  1. The JDK usually installed in the C:\Program Files\Java directory by default.
  2. Under this directory we can find one or more versions of installed JDK, for examples I have jdk-14 and jdk-17. Just choose the default one we’re going to use.

Step 2. Setting JAVA_HOME variable

After we know the location of your JDK installation, we can copy the directory location from the Windows Explorer address bar.

  1. Open Windows Explorer
  2. Right-Click the Computer and select the Properties menu.
  3. Click Advanced system settings and the System Properties windows will be shown.
  4. Select the Advance tab.
  5. Click the Environment Variables button.
  6. A new Environment Variables window will be shown.
  7. Under the System Variables, click the New button to create a new environment variable.
  8. Enter the variable name as JAVA_HOME, all letters are in uppercase.
  9. In the variable value enter the JDK installation path you’ve copy above.
  10. Click OK.

Step 3. Setting the Path variable

After we’ve set the JAVA_HOME variable, now we can update the Path variable.

  1. In the Environment Variables window, under the System Variables section find a variable named Path.
  2. If we don’t have the Path variable we need to add one using the New button.
  3. If we already have the Path variable we’ll need to update its value, click Edit button to update.
  4. Add %JAVA_HOME%\bin; to the beginning of the Path variable value.
  5. Press OK to when we are done.
  6. Press another OK to close the Environment Variables window.

Step 4. Check to see if the settings work

  1. Open your Windows Command Prompt.
  2. Type java -version in the command line.
  3. If everything was set correctly we’ll see the running version of your installed Java JDK.

As an example on my Windows Command Prompt I have something like:

D:\>java -version
java version "17" 2021-09-14 LTS
Java(TM) SE Runtime Environment (build 17+35-LTS-2724)
Java HotSpot(TM) 64-Bit Server VM (build 17+35-LTS-2724, mixed mode, sharing)

If you don’t see the correct output, for instance you get an error like “‘java’ is not recognized as an internal or external command, operable program or batch file.”, please retry the steps described above. Enjoy your new adventure with Java programming. Happy coding!

How to establish connection to a database using Properties object?

In the following code snippet, you will see how to pass some connection arguments when connecting to a database. To do this, we can use the java.util.Properties class. We can put some key value pairs as a connection arguments to the Properties object
before we pass this information into the DriverManager class.

Let’s see the example below:

package org.kodejava.jdbc;

import java.sql.*;
import java.util.Properties;

public class GetConnectionWithProperties {
    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) {
        GetConnectionWithProperties demo = new GetConnectionWithProperties();
        try (Connection connection = demo.getConnection()) {
            // do something with the connection.
            Statement stmt = connection.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT * FROM product");
            while (rs.next()) {
                System.out.println("Code = " + rs.getString("code"));
                System.out.println("Name = " + rs.getString("name"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private Connection getConnection() throws SQLException {
        Properties connectionProps = new Properties();
        connectionProps.put("user", USERNAME);
        connectionProps.put("password", PASSWORD);

        Connection connection = DriverManager.getConnection(URL, connectionProps);
        System.out.println("Connected to database.");
        return connection;
    }
}

Maven Dependencies

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

Maven Central

How to define JRadioButton label position?

In this code snippet you’ll see how to define JRadioButton label position. By default, the label will be displayed on the right side of the button. In the code below you will see some examples for placing the label on the left side, at the top and the bottom of the JRadioButton.

To define the label position we use the combination of the setHorizontalTextPosition() and setVerticalTextPosition() method and specified the position using one of the available constant in SwingConstants interface.

package org.kodejava.swing;

import javax.swing.*;

public class RadioButtonLabelPosition {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();

        // Create JRadioButton with label on the right
        JRadioButton button1 = new JRadioButton("Button One");
        button1.setHorizontalTextPosition(SwingConstants.RIGHT);

        // Create JRadioButton with label on the left
        JRadioButton button2 = new JRadioButton("Button Two");
        button2.setHorizontalTextPosition(SwingConstants.LEFT);

        // Create JRadioButton with label at the bottom centered.
        JRadioButton button3 = new JRadioButton("Button Three");
        button3.setVerticalTextPosition(SwingConstants.BOTTOM);
        button3.setHorizontalTextPosition(SwingConstants.CENTER);

        // Create JRadioButton with label at the top centered.
        JRadioButton button4 = new JRadioButton("Button Four");
        button4.setVerticalTextPosition(SwingConstants.TOP);
        button4.setHorizontalTextPosition(SwingConstants.CENTER);

        panel.add(button1);
        panel.add(button2);
        panel.add(button3);
        panel.add(button4);

        frame.add(panel);
        frame.setSize(500, 300);
        frame.setVisible(true);
    }
}

Here is a screen capture result of the code snippet above:

JRadioButton Label Position

How to truncate a string after n number of words?

package org.kodejava.regex;

public class GetNumberOfWordsFromString {
    public static void main(String[] args) {
        String text = "The quick brown fox jumps over the lazy dog.";

        String one = truncateAfterWords(1, text);
        System.out.println("1 = " + one);

        String two = truncateAfterWords(2, text);
        System.out.println("2 = " + two);

        String four = truncateAfterWords(4, text);
        System.out.println("4 = " + four);

        String six = truncateAfterWords(6, text);
        System.out.println("6 = " + six);
    }

    /**
     * Truncate a string after n number of words.
     *
     * @param words number of words to truncate after.
     * @param text  the text.
     * @return truncated text.
     */
    public static String truncateAfterWords(int words, String text) {
        String regex = String.format("^((?:\\W*\\w+){%s}).*$", words);
        return text.replaceAll(regex, "$1");
    }
}

The result of the snippet:

1 = The
2 = The quick
4 = The quick brown fox
6 = The quick brown fox jumps over