}
}
Exception in thread "main" java.lang.NullPointerException
at cn.itheima.test4.TraversalList.showDir(TraversalList.java:37)
at cn.itheima.test4.TraversalList.showDir(TraversalList.java:41)
at cn.itheima.test4.TraversalList.showDir(TraversalList.java:41)
at cn.itheima.test4.TraversalList.getDirList(TraversalList.java:15)
at cn.itheima.test4.TraversalListTest.main(TraversalListTest.java:15)