NetBeans项目会折叠树状菜单,但这不是在早期发生的。Product Version: NetBeans IDE 7.4 (Build 201310111528)Java: 1.7.0_45; Java HotSpot(TM) 64-Bit Server VM 24.45-b08
Runtime: Java(TM) SE Runtime Environment 1.7.0_45-b18
Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to library.Itemat library.Item.compareTo(Item.java:8) at java.util.TreeMap.remove(T