Editor does not contain a main type错误提示，怎么解决？

I am trying to run some java files in a new PRoject.So I make the project,put the files in it and I try to RUN the main file so my error problems happened!!!

Thanks for the stack overflow.

the Answer: Right click on the folder where you put your main class then click onBuild Path--> Use as Source Folder.

It worked!!!

OR-->

right click on the package->properties->Java Build Path->Add folder(select the folder your code reside in)

Do work either!!!

好累啊！！！

错误：找不到或无法加载主类。

解决办法：右键工程文件夹-->Build Path-->Use as Source Folder 就解决了。

完美运行！