The user operation is waiting for "Building workspace" to complete.

我用eclipse建立了一个空的Dynamic Web Project,在src下新建了包,并在该包下创建了一个类,很简单的main函数程序,当我run as Java application,出现了这个,摸不着头脑。The user operation is waiting for "Building workspace" to complete.
解决方法:先Project->Build Automatically去勾选,再执行。

run as application 和run on server 区别

前者是运行Java的程序中包含main方法。
后者是运行一个web应用程序,不需要main方法。