mysql-[jbdc]打開 connection 空指針異常

[jbdc]打開 connection 空指針異常

小白才開始學JBDC 這是網上照著寫的代碼……
出現了

Exception in thread "main" java.lang.NullPointerException
at FirstExample.main(FirstExample.java:23)

空指針異常
但是不知道怎麼改，求解。謝謝了

import java.sql.*;
public class FirstExample {
//JDBC driver name and databaase URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/EMP";

//Database credentials
static final String USER = "root";
static final String PASS = "2573718";

public static void main(String args[]) throws ClassNotFoundException{
    Connection conn = null;
    Statement stmt = null;
    try{
        //注冊 JDBC driver
        Class.forName("com.mysql.jdbc.Driver");

        //打開 a connection
        System.out.println("Connecting to database..");
        stmt = conn.createStatement();
        String sql;
        sql= "SELECT s_no  FROM student";
        ResultSet rs = stmt.executeQuery(sql);

        //插入數據
        while(rs.next())
        {
            int no = rs.getInt("s_no");
            String name = rs.getString("s_name");

            System.out.println("NO"+no);
            System.out.println("Name"+name);
        }
        rs.close();
        stmt.close();
        conn.close();
    }
    catch(SQLException se){
        se.printStackTrace();
    }
    finally{
        try{
            if(stmt!=null)
                stmt.close();
            }
        catch(SQLException se2){

        }
        try{
            if(conn!=null)
                conn.close();
        }
        catch(SQLException se){
            se.printStackTrace();
        }
    }
}

}

最佳回答：

你的數據庫可能有問題，裡邊的字符不對