java值在从ArrayList转换为ArrayAndroid时交换

Question

我有一个ArrayList，它有一些元素。此列表中的项目将重复。我想将相似的值分组并将其转换为数组

目前我的ArrayList是：-

ArrayList<String> isonC = new ArrayList<String>();

isonC的值=`[a，a，a，b，c，c，c，c，c，d，d，d，d，d，d，d] 我认为：-

icons = isonC.toArray(new String[isonC.size()]);
icons = new HashSet<String>(Arrays.asList(icons)).toArray(new String[0]);

我得到的值如下：- 图标=[a, c, b,d]

鉴于元素的实际顺序应为：-

[a,b, c,d]

为什么第二和第三个值互换

任何建议都会有帮助。 谢谢

Answer 1

尝试使用TreeSet而不是HashSet。请尝试以下方法：-

TreeSet<String> mySet =  new TreeSet <String>(myArrayList);
myArray =  mySet.toArray(new String[mySet.size()]);

Answer 2

从documentation到LinkedHashSet：

Hash table and linked list implementation of the Set interface, with predictable iteration order. This implementation differs from HashSet in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is the order in which elements were inserted into the set (insertion-order). Note that insertion order is not affected if an element is re-inserted into the set. (An element e is reinserted into a set s if s.add(e) is invoked when s.contains(e) would return true immediately prior to the invocation.)

因此，假设您希望在oldArray中出现较早的项在newArray中出现较早，则以下操作应该可以工作：

String[] newArray = new LinkedHashSet<String>(Arrays.asList(oldArray)).toArray(new String[0]);