获取副本的数目从ArrayList中 [英] Get number of duplicates from ArrayList

问题描述

举例来说，假设我有一个的ArrayList 可能包含以下值：

For example, say I have an ArrayList that could contain the following values:

x
x
x
y
y

现在我想要检索的 X 的数量和 X ，我希望能够区分我有什么，无论是 X 或是，因为在现实中，我能有ArrayList中的任何对象，我要能告诉他们分开。结果

Now what I want to retrieve is the number of x and x and I want to be able to differentiate what I have, either x or y because in actuality, I could have any object in the ArrayList and I have to be able to tell them apart.

我在想什么做的第一次转换的的ArrayList 到 LinkedHashSet ，这将保持排序和删除重复的，所以我只想有 X 和是但是，我怎么会得到每一个数，并将其与关联正确的元素？结果

What I was thinking of doing was first converting the ArrayList into a LinkedHashSet, which would keep the ordering and remove the duplicates so I would just have x and y But how would I get the number of each and associate it with the proper element?

总之我想要做的是能写一个的toString 方法，可以让我的输出：

Overall what I want to do is to be able to write a toString method that will let me output:

x3y2

但不知道该 X 和是是因为他们本来是别的东西，如元素以Z 或是W 。

But without knowing that x and y are the elements because they could have been something else like z or w.

推荐答案

退房多集在谷歌番石榴：<一href=\"http://docs.guava-libraries.google$c$c.com/git-history/v11.0.2/javadoc/com/google/common/collect/Multiset.html\" rel=\"nofollow\">http://docs.guava-libraries.google$c$c.com/git-history/v11.0.2/javadoc/com/google/common/collect/Multiset.html

Check out the Multiset in google guava: http://docs.guava-libraries.googlecode.com/git-history/v11.0.2/javadoc/com/google/common/collect/Multiset.html

例如：

Multiset<String> strings = HashMultiset.create(arrayList);
int countX = strings.count("x"); // the count of x

更多的例子可以在番石榴维基

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