How do I delete record from table?

In this example we are showing you how to delete a record from table in the database. We use a standard JDBC library for this purpose. For the database we use MySQL, you can use any type of database you want. All you need to do is to find the JDBC driver for the database and configure it accordingly.

So here is the code example for deleting records from a table in database.

package org.kodejava.example.sql;

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

public class DeleteRecordExample {
    public static void main(String[] args) throws Exception {
        // This is our connection url to MySQL database, where jdbc is the
        // prefix for all jdbc connection. The mysql sub telling that we
        // are using MySQL database. Localhost is where our database is
        // reside and kodejava is our database name.
        String url = "jdbc:mysql://localhost/kodejava";

        // To connect to a database we will need a user and password for
        // the database server to allow us to manipulate its database.
        String username = "kodejava";
        String password = "kodejava123";

        Connection connection = null;
        try {
            // Load the jdbc driver class
            Class.forName("com.mysql.jdbc.Driver");
            // Then we ask a connection from the DriverManager by passing
            // the connection URL and the password.
            connection = DriverManager.getConnection(url, username, password);

            // To delete records from tables we create an SQL delete command.
            // The question mark that we used in the where clause will be the
            // holder of value that will be assigned by PreparedStatement
            // class.
            String sql = "DELETE FROM m_users WHERE id = ?";
            int id = 2;

            // Create a statement object. We use PreparedStatement here.
            PreparedStatement statement = connection.prepareStatement(sql);

            // Pass a value of a userId that will tell the database which
            // records in the database to be deleted. Remember that when
            // using a statement object the index parameter is start from
            // 1 not 0 as in the Java array data type index.
            statement.setInt(1, id);

            // Tell the statement to execute the command. The executeUpdate()
            // method for a delete command returns number of records deleted
            // as the command executed in the database. If no records was
            // deleted it will simply return 0
            int rows = statement.executeUpdate();

            System.out.println(rows + " record(s) deleted.");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null && !connection.isClosed()) {
                connection.close();
            }
        }
    }
}

How do I delete a file?

In this example you will see how to delete file. To delete a file we start by creating a File object that represent the file to be deleted. Next we can use the exists() to check if the file is exists before we delete it. Finally to delete the file we call the delete() method of the File object to delete the file. If the file was successfully deleted the method will return a boolean true result, otherwise it will return false.

package org.kodejava.example.io;

import java.io.File;

public class FileDeleteExample {
    public static void main(String[] args) {
        // When want to delete a file named readme.txt
        File file = new File("readme.txt");

        // Checks if the file is exists before deletion.
        if (file.exists()) {
            System.out.println("Deleting file " + file.getAbsolutePath());
            // Use the delete method to delete the given file.
            file.delete();
        } else {
            System.out.println(file.getAbsolutePath() + " doesn't exists.");
        }
    }
}