A cycle was detected in the build path of project

解决Eclipse中Java工程间循环引用而报错的问题 
如果我们的项目包含多个工程（project），而它们之间又是循环引用的关系，那么Eclipse在编译时会抛出如下一个错误信息： 
“A cycle was detected in the build path of project: XXX” 
解决方法非常简单： 
Eclipse Menu -> Window -> Preferences... -> Java -> Compiler -> Building -> Building path problems -> Circular dependencies -> 将Error改成Warning