我的密码是

import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.datastax.driver.core.BatchStatement;
import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.LocalDate;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;
import com.datastax.driver.core.PreparedStatement;
public class DataPortCluster {
    private static Cluster cluster; 
    private static Session session;
    public static Cluster connect(String node) {
        return Cluster.builder().addContactPoint(node).build();
    }
    public static void main(String[] args) throws Exception{ 
        Connection conn = null;
        Statement  stm = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String host = "jdbc:mysql://localhost:3306/ksfedata";
            String uName = "root";
            String uPass= "root";
            conn= DriverManager.getConnection(host, uName, uPass);
            stm = conn.createStatement();
            String sql = "SELECT c.id, c.branch, c.firstName, c.lastName, c.dob, c.uniqueId, c.mobilePhone, c.isKSFEEmployee "
                    + ",CONCAT_WS('',offaddress.line1,offaddress.line2, offaddress.pinCode) AS Official,"
                    + "CONCAT_WS('',peraddress.line1,peraddress.line2, peraddress.pinCode) AS Permanent,"
                    + "CONCAT_WS('',resaddress.line1,resaddress.line2, resaddress.pinCode) AS Residential,"
                    + "CONCAT_WS('',tempaddress.line1,tempaddress.line2, tempaddress.pinCode) AS Temporary,"
                    + "CONCAT_WS('',commaddress.line1,commaddress.line2, commaddress.pinCode) AS Communication"
                    + " FROM customerdup c  "
                    + "LEFT JOIN customeraddressdup as offaddress ON (offaddress.customerId =c.id AND  offaddress.customerBranch = c.branch  AND offaddress.addresstype=0) "
                    + "LEFT JOIN customeraddressdup as peraddress ON (peraddress.customerId =c.id AND  peraddress.customerBranch = c.branch  AND peraddress.addresstype=1) "
                    + "LEFT JOIN customeraddressdup as resaddress ON (resaddress.customerId =c.id AND  resaddress.customerBranch = c.branch  AND resaddress.addresstype=2) "
                    + "LEFT JOIN customeraddressdup as tempaddress ON (tempaddress.customerId =c.id AND  tempaddress.customerBranch = c.branch  AND tempaddress.addresstype=3) "
                    + "LEFT JOIN customeraddressdup as commaddress ON (commaddress.customerId =c.id AND  commaddress.customerBranch = c.branch  AND commaddress.addresstype=4)";
            //          String sql = "Select ID,FIRSTNAME,DOB,MOBILEPHONE,EMAIL From customerdup LIMIT 3";
            ResultSet rst;
            rst = stm.executeQuery(sql);
            String serverIp = "localhost";
            String keyspace = "events";
            cluster = Cluster.builder().addContactPoint(serverIp).build();
            session = cluster.connect(keyspace);
            PreparedStatement statement = session.prepare("insert into customer (branch, uniqueid, communication,customerid,dob,firstname,isksfeemp,lastname,mobile,official,permanent,residential,temporary) "
                    + "values (?,?,?,?,?,?,?,?,?,?,?,?,?) ;");
            //BoundStatement boundStatement = new BoundStatement(statement);
            BatchStatement batchStatement = new BatchStatement();
            long startTime = System.nanoTime();
            while (rst.next()) { 
                int id = rst.getInt("id");
                String branch = rst.getString("branch");
                String firstname = rst.getString("firstname");
                String lastname = rst.getString("lastname");
                Date datecheck = rst.getDate("dob");
                LocalDate dob = LocalDate.fromMillisSinceEpoch(datecheck.getTime());
                String uniqueId =  rst.getString("uniqueId");
                String mobile = rst.getString("mobilePhone");
                int isKSFEEmployee = rst.getInt("isKSFEEmployee");
                String Official = rst.getString("Official");
                String Permanent = rst.getString("Permanent");
                String Residential = rst.getString("Residential");
                String Temporary = rst.getString("Temporary");
                String Communication = rst.getString("Communication");
                batchStatement.add(statement.bind(branch,uniqueId,Communication,id,dob,firstname,isKSFEEmployee,lastname,mobile,Official,Permanent,Residential,Temporary));
                //session.execute(boundStatement.bind(id,name,Dob,mobNo,email));
            }
            session.execute(batchStatement);
            long endTime   = System.nanoTime();
            long totalTime = endTime - startTime;
            System.out.println(totalTime + "++++++++++++++555555555555555555555555555555555555555555555");
            String cqlStatement = "SELECT * FROM customer";
            for (Row row : session.execute(cqlStatement)) {
                System.out.println(row.toString());
            } 
        }catch (Exception e) {
            System.out.println(e.getMessage());
        }
        finally {
            if (conn != null && stm != null) {
                try {
                    conn.close();
                    stm.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
                conn = null;
            }
            session.close();
            cluster.close();
        }
    }
}

当我试着调试我的代码时，我遇到了一个错误

Exception in thread "main" java.lang.NullPointerException
    at DataPortCluster.main(DataPortCluster.java:121)

在那条线上

cluster = Cluster.builder().addContactPoint(serverIp).build();

不知道是什么问题。如果有人能帮忙的话，那将是非常值得赞赏的。在我看来，问题是发生在连接Cassandra。为什么会在上面的行中抛出错误。我给出的serverip是localhost。
提前谢谢