Unable to open class file No such file or directory

创建新工程的时候，会发生如下错误：
  Unable to open class file No such file or directory

解决方法：1.重启eclipse,错误消失

2.网络上普遍的解决方法：
Solution:解决方法：

The “Build Path” for your Java environment is not setup correctly in Eclipse. To fix this, follow these steps:

1) Open the Preferences Window by clicking “Window -> Preferences”

2) Find the “Java” section and expand it

3) Select “Build Path”

4) Change the value of Source and output folder from Folders to “Project”

5) Click Apply and then “OK”

Your problem should be resolved!