How do I query records from a table?

By Wayan in JDBC 0 Comment 
package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class JdbcQueryExample {
    // Database connection information
    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) {
        // Get a connection to database.
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            // Create a statement object.
            Statement statement = connection.createStatement();

            // Executes a query command to select isbn and the book title
            // from books table. The execute query returns a ResultSet
            // object which is the result of our query execution.
            String query = "SELECT isbn, title, published_year FROM book";
            ResultSet books = statement.executeQuery(query);

            // To get the value returned by the statement.executeQuery we
            // need to iterate the books object until the last items.
            while (books.next()) {
                // To get the value from the ResultSet object we can call
                // a method that correspond to the data type of the column
                // in database table. In the example below we call
                // books.getString("isbn") to get the book's ISBN 
                // information.
                System.out.println(books.getString("isbn") + ", " +
                        books.getString("title") + ", " +
                        books.getInt("published_year"));
            }
        } catch (Exception 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 get my screen size?

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

import java.awt.*;

public class ScreenSizeExample {
    public static void main(String[] args) {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

        System.out.println("Screen Width: " + screenSize.getWidth());
        System.out.println("Screen Height: " + screenSize.getHeight());
    }
}

The output of the code snippet above:

Screen Width: 2560.0
Screen Height: 1080.0

How do I determine if a pathname is a directory?

By Wayan in Core API, IO 0 Comment

To determine if an abstract pathname is a directory we can use the File.isDirectory() method. Here is an example code.

package org.kodejava.io;

import java.io.File;

public class IsDirectoryExample {
    public static void main(String[] args) {
        // Creates a instance of File.
        File file = new File("C:/Users/wsaryada");

        // Check if the abstract pathname is a directory by calling
        // isDirectory() method of the File class.
        if (file.isDirectory()) {
            System.out.println("This file is a directory.");
        } else {
            System.out.println("This is just an ordinary file.");
        }
    }
}

How do I get total space and free space of my disk?

By Wayan in Core API, IO 0 Comment 
package org.kodejava.io;

import java.io.File;

public class FreeSpaceExample {
    public static void main(String[] args) {
        // We create an instance of a File to represent a partition
        // of our file system. For instance here we used a drive D:
        // as in Windows operating system. 
        File file = new File("D:");

        // Using the getTotalSpace() we can get an information of
        // the actual size of the partition, and we convert it to
        // mega bytes. 
        long totalSpace = file.getTotalSpace() / (1024 * 1024);

        // Next we get the free disk space as the name of the
        // method shown us, and also get the size in mega bytes.
        long freeSpace = file.getFreeSpace() / (1024 * 1024);

        // Just print out the values.
        System.out.println("Total Space = " + totalSpace + " Mega Bytes");
        System.out.println("Free Space = " + freeSpace + " Mega Bytes");
    }
}

Here is the result of the program:

Total Space = 1907605 Mega Bytes
Free Space = 946213 Mega Bytes

How do I rename a file or directory?

By Wayan in Core API, IO 0 Comment 
package org.kodejava.io;

import java.io.File;
import java.io.IOException;

public class FileRenameExample {
    public static void main(String[] args) throws IOException {
        // Creates a new file called OldHouses.csv
        File oldFile = new File("OldHouses.csv");
        boolean created = oldFile.createNewFile();
        System.out.println("File created? " + created);

        // Creates the target file.
        File newFile = new File("NewHouses.csv");

        // The renameTo() method renames file or directory to a
        // new name by passing the new destination file.
        boolean renamed = oldFile.renameTo(newFile);
        System.out.println("File renamed? " + renamed);
    }
}