数据库学习问题

java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC][SQLServer]用户 'sa' 登录失败。at com.microsoft.jdbc.base.BaseExceptions.createException(Unknown Source)at com.microsoft.jdbc.base.BaseExceptions.getException(Unknown Source)at com.microsoft.jdbc.sqlserver.tds.TDSRequest.processErrorToken(Unknown Source)at com.microsoft.jdbc.sqlserver.tds.TDSRequest.processReplyToken(Unknown Source)at com.microsoft.jdbc.sqlserver.tds.TDSLoginRequest.processReplyToken(Unknown Source)at com.microsoft.jdbc.sqlserver.tds.TDSRequest.processReply(Unknown Source)at com.microsoft.jdbc.sqlserver.SQLServerImplConnection.open(Unknown Source)at com.microsoft.jdbc.base.BaseConnection.getNewImplConnection(Unknown Source)at com.microsoft.jdbc.base.BaseConnection.open(Unknown Source)at com.microsoft.jdbc.base.BaseDriver.connect(Unknown Source)at java.sql.DriverManager.getConnection(DriverManager.java:620)at java.sql.DriverManager.getConnection(DriverManager.java:200)at FS.UpdateStu.getConnection(UpdateStu.java:13)at FS.UpdateStu.main(UpdateStu.java:23)Exception in thread "main" java.lang.NullPointerExceptionat FS.UpdateStu.main(UpdateStu.java:25)