找不到符号：queryexecuter且找不到符号：queryreturner

Question

我正在尝试制作注册表单，在数据库（oracle）中注册用户但显示错误 -

cannot find symbol
  symbol:   method queryExecuter(String)
  location: variable x of type DBConnect
----

cannot find symbol
  symbol:   method queryReturner(String)
  location: variable x of type DBConnect
----

仅在RegisterUser.java文件中显示错误  代码 -

DBConnect.java -

import java.sql.*;

public class DBConnect {
    Connection conn = null;

    public DBConnect() throws Exception {
        Class.forName("oracle.jdbc.OracleDriver");
        Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "system", "9424705385");

    }

    public void queryExecuter(String sql) throws Exception {
        // for insert, update and Delete DML
        Statement stat = conn.createStatement();
        stat.execute(sql);
        stat.close();
        conn.close();
    }

    public ResultSet queryReturner(String sql) throws Exception { // select statement
        Statement stat = conn.createStatement();
        ResultSet rs = stat.executeQuery(sql);
        return rs;
    }
}

RegisterUser.java -

import java.sql.*;

public class RegisterUser {

    public void insertUser(String email, String pass, String name, String mobile) throws Exception {
        String sql = "insert into webreg  value('" + email + "','" + pass + "','" + name + "','" + mobile + "')";
        DBConnect x = new DBConnect();
        x.queryExecuter(sql); // line showing error
    }

    public ResultSet getAllUser() throws Exception

    {
        DBConnect x = new DBConnect();
        ResultSet rs = x.queryReturner("select * from webreg"); // line showing error
        return rs;

    }

}

我没有添加任何jar文件，除了ojdb6 jar，所以我必须添加任何jar文件吗？