The project was not built due to "Could not delete ''.". Fix the problem, then try refreshing this p

Eclipse修改完Java类文件保存之后，项目上出现了错误提示，如图：

但是项目的文件都没有提示错误，
打开Problems窗口会看到具体的错误信息：
The project was not built due to “Could not delete ”.”. Fix the problem, then try refreshing this project and building it since it may be inconsistent SimpleMetadataReaderTest Unknown Java Problem
如图：

错误原因

项目生成的目标目录在资源管理器中打开了，生成时需要清理目录，由于文件夹打开了无法删除，所以导致些错误。

解决方案

关闭对应的文件夹就可以了。