import sun.management.ManagementFactory,我在rt包下已经找到sun.management.ManagementFactory，但是就是有才错，请问怎么回事。
------解决方案--------------------
Access restriction: The type ManagementFactory is not accessible due to restriction on required library D:\cdmInstall\glassfish3\jdk\jre\lib\rt.jar
访问限制： 不让访问rt.jar里面的