import java.sql.*;

public class test
{
   public static void main(String[] args) throws Exception
   {
      String URL = "jdbc:mysql://localhost/kmng";
      String USER = "root";
      String PASS = "";
      String DRIVER = "com.mysql.jdbc.Driver";

      DriverManager.registerDriver((Driver) Class.forName(DRIVER).newInstance());
      
      Connection con = DriverManager.getConnection(URL, USER, PASS);      

      Statement st = con.createStatement();
      ResultSet res = st.executeQuery("SELECT text FROM error WHERE id=1");
      if(res.next()) {
        Clob c = res.getClob(1);
        c.truncate(0);
        c.setString(1,"öööööö");
        PreparedStatement stmt = con.prepareStatement ( "UPDATE error SET text = ? WHERE id=1");
        stmt.setClob ( 1, c );
        stmt.executeUpdate();
        stmt.close();
       }
      res.close();
      st.close();
      con.close();
   }
}