这里有两种方法帮你删除在一个ArrayList里重复的elements。下面的程序片段里，removeDuplicate方法不维护顺序 (Order)，而removeDuplicateWithOrder方法会保持顺序 (Order)，但会有些性能上的牺牲。
The removeDuplicate Method:
/** List order not maintained **/ public static void removeDuplicate(ArrayList arlList) { HashSet h = new HashSet(arlList); arlList.clear(); arlList.addAll(h); }
The removeDuplicateWithOrder Method:
/** List order maintained **/ public static void removeDuplicateWithOrder(ArrayList arlList) { Set set = new HashSet(); List newList = new ArrayList(); for (Iterator iter = arlList.iterator(); iter.hasNext(); ) { Object element = iter.next(); if (set.add(element)) newList.add(element); } arlList.clear(); arlList.addAll(newList); }
原文：http://www.cnblogs.com/luhaoming/p/3998231.html