错误记录 Unable to compile class for JSP

org.apache.jasper.JasperException: Unable to compile class for JSP:

An error occurred at line: [10] in the jsp file: [/init3.jsp]
TestCPU cannot be resolved
7:

8:
9:
10: <%TestCPU.testCPU();%>
11: CPU usage is controlled in Sin shape!

12: Thread Counter:<%=TestCPU.threadList.size()%>
13:

An error occurred at line: [12] in the jsp file: [/init3.jsp]
TestCPU.threadList cannot be resolved to a type
9:
10: <%TestCPU.testCPU();%>
11: CPU usage is controlled in Sin shape!

12: Thread Counter:<%=TestCPU.threadList.size()%>
13:
14:

Stacktrace:
org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:103)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:213)
org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:473)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:392)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:362)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:346)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:603)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:399)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

要运行的页面是这个

看了网上的一些解决方法，大部分是jar包的问题，未导入或包冲突，但我的问题是webapp文件夹里没有我编译的.class文件，最后clean一下ok了。不得不说eclipse太狗了。