Java Database Connectivity (JDBC)

i used hxtt driver for performing dbf operations, so far working well except it takes hours (or maybe days) to execute delete/insert with million datas. In fact i never seen its result because it takes more than 20 hours to perform delete some records of 1800907 datas. So, i don't know, the action finish completely with hours or it just never ending process ?

below i post my code :

import java.util.*;
import java.sql.*;
import java.io.*;
import com.hxtt.sql.*;

public class TestDbf {
    
    Connection connection;
    /** Creates a new instance of TestDbf */
    public TestDbf(String path) {
        Properties prop = new Properties();
        prop.setProperty("user", "");
        prop.setProperty("OtherExtensions","true");
        prop.setProperty("Version Number", "03");        
        try {
            Class.forName("com.hxtt.sql.dbf.DBFDriver").newInstance();
            connection = DriverManager.getConnection("jdbc:DBF:///"+path, prop); 
        }
        catch(SQLException sqx) {
            System.out.println("SQL Error when connecting to database");
            sqx.printStackTrace();
        }
        catch (ClassNotFoundException cfx) {
            System.out.println("could ot find HXTT class, make sure the classpath have been defined in your system !");
            cfx.printStackTrace();
        }          
        catch(Exception e) {
            e.printStackTrace();
        }        
    }
    
    public void createIndex(String tablename, String colname, String idxname) {
        try {
            Statement stmt = connection.createStatement();
            String sqlIndex = "create index "+idxname+" on \""+tablename+"\" ("+colname+")";
            boolean isCreated = stmt.execute(sqlIndex);
            stmt.close();
        }
        catch(SQLException sqx) {
            sqx.printStackTrace();
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }
    
    public void deleteData(String tablename) {
        try {
            Statement stmt = connection.createStatement();
            String sql = "delete from \""+tablename+"\" where exists (select 'x' from pp where trim(wcode)='54' and kdpp = 

kdppx)";
            boolean isDeletedKdpp1 = stmt.execute(sql);
            stmt.close();
        }
        catch(SQLException sqx) {
            sqx.printStackTrace();
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] arg) {
        TestDbf dbf = new TestDbf("C:\\TestDbf");
        dbf.createIndex("71280206.PH8", "kdppx", "KDPPIDX71280206");
        dbf.deleteData("71280206.PH8");
    }
    
}

in above code, user just perform creating index and deleting data which involved two tables, pp.dbf (6045 records) and 71280206.PH8 (1800907 records). SQL Statement for delete action is just :
"delete from "71280206.PH8" where exists (select 'x' from pp where trim(wcode)='54' and kdpp = kdppx)".

why this action needs hours or days or hang ? (after it ran 20 hours i closed the application, so i don't know exactly when
the application will finish completely).

regards,
rtery