这是我运行你的mysql与eclipse代码出的错误
Exception in thread "AWT-EventQueue-0" java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)lianjiecuowu
java.lang.NullPointerException: Cannot invoke "java.sql.Connection.prepareStatement(String)" because "con" is null
at 学生管理系统/学生管理系统.Dbcon.query(Dbcon.java:48)
at 学生管理系统/学生管理系统.Qframe$6.actionPerformed(Qframe.java:91)
at java.desktop/java.awt.AWTEventMulticaster.actionPerformed(AWTEventMulticaster.java:451)
at java.desktop/java.awt.Button.processActionEvent(Button.java:417)
at java.desktop/java.awt.Button.processEvent(Button.java:385)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4993)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4825)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
这个系统中的配置文件看一下，是否跟自己的环境一致。
检查数据源的配置（数据库名、用户名、密码等）
数据库的版本和数据库驱动包的版本要一致。
很明显呀，你运行人家的代码，都不带修改的吗？比如说把人家的数据库信息改成自己的，版本最好也比对一下，你运行人家的代码之前先将数据库sql文件导入到你的数据库中，命名最好和人家的一致，当然也可自定义，其次修改他的账号密码换成自己的数据库账号密码
这句就是提示你账号密码有误
Access denied for user 'root'@'localhost' (using password: YES)