急 MyEclipse的一个问题

[haaini]

我用MyEclipse+tomcat+sql server+jsp做的一个东西，已经做好了的，早上还好好的，晚上再打开时出现了好多错误，例如String无法解决，java.lang.object无法解决之类的，重新编译运行后的错误如下：
2010-5-10 19:38:54 org.apache.catalina.core.ApplicationContext log
信息: Marking servlet LoginServlet as unavailable
2010-5-10 19:38:54 org.apache.catalina.core.StandardWrapperValve invoke
严重: Allocate exception for servlet LoginServlet
java.lang.Error: Unresolved compilation problems:
The import java.io.IOException cannot be resolved
The import java.io.PrintWriter cannot be resolved
The hierarchy of the type LoginServlet is inconsistent
No exception of type ServletException can be thrown; an exception type must be a subclass of Throwable
IOException cannot be resolved to a type
No exception of type ServletException can be thrown; an exception type must be a subclass of Throwable
IOException cannot be resolved to a type
String cannot be resolved to a type
String cannot be resolved to a type
String cannot be resolved to a type
String cannot be resolved
String cannot be resolved to a type
No exception of type ServletException can be thrown; an exception type must be a subclass of Throwable

at com.StuInfo.ctrl.LoginServlet.<init>(LoginServlet.java:3)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1116)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:809)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:129)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)
at java.lang.Thread.run(Thread.java:619)

是不是jdk有问题，检查了下jdk，引用得也没有问题啊，但是我今天没有动过电脑啊，只是用了word而已，难道中毒了吗

[jzshmyt]

删除tomcat的work目录,如果还不行就选择project-->clean

[haaini]

已经解决啦 把jdk重新取个名字引进来就行啦 也不知道为什么会这样