myeclipse中增加user libraries时出现了“ One or more selected libraries are already on the build path”：
很奇怪，明明已经将相应jar包导入，系统却报了这个错。后来发现将jar放入lib文件夹后还要在myeclipse中lib文件夹右键刷新一下，否则系统识别不到。
myeclipse中增加user libraries时出现“ One or more selected libraries are already on the build path”时的解决办法
原文：http://blog.csdn.net/dongdong9223/article/details/44080589
