myeclipse中增加user libraries时出现“ One or more selected libraries are already on the build path”时的解决方法

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

    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。