How should you properly close a connection in a database or network protocol?

Properly closing a connection in a database or network protocol involves closing all open resources to prevent memory leaks and locks. In Java, working with a database typically uses try-with-resources or explicitly calls the close() method in a finally block.

Example with JDBC:

try (Connection conn = DriverManager.getConnection(url, user, password);
     PreparedStatement stmt = conn.prepareStatement(query);
     ResultSet rs = stmt.executeQuery()) {
    while (rs.next()) {
        // process result
    }
} catch (SQLException e) {
    e.printStackTrace();
}
// Resources are automatically closed here

If try-with-resources is not used, then closing should be done in a finally block:

Connection conn = null;
try {
    conn = DriverManager.getConnection(url, user, password);
    // work with connection
} catch (SQLException e) {
    e.printStackTrace();
} finally {
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

For network connections (e.g., sockets), it is also important to call the close() method after work is finished to free resources and properly close the connection.