import  java.sql.*;
 class  test 
{
     public   static   void  main(String[] args)  throws  SQLException, ClassNotFoundException
    {
         Class .forName("oracle.jdbc.driver.OracleDriver");
        Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@<host>:1521:<db_name>", "user", "pass");
        CallableStatement cstmt = conn.prepareCall(
                "declare l_tmp varchar2(4000):=?; begin execute immediate 'select '||l_tmp||' from dual' into ?; end;");
        cstmt.setString( 1 , args[ 0 ]);
        cstmt.registerOutParameter( 2 , Types.INTEGER);
        cstmt.executeUpdate();
        System.out.println(cstmt.getInt( 2 ));
        conn.close();
    }
}