java 如何将多个集合相交？
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How to intersect multiple sets?
提问by vale4674
I have this list:
我有这个清单：
private List<Set<Address>> scanList;
So my list contains multiple scans as you can see. After each scan I add new set into the list.
如您所见，我的列表包含多个扫描。每次扫描后，我将新集合添加到列表中。
After all scans are finished I would like to take only the addresses that occur in every set and put it into:
完成所有扫描后，我只想将每组中出现的地址放入：
private List<Address> addresses;
Does something like this already exists in Set/TreeSet/HashSet?
Set/TreeSet/HashSet 中是否已经存在类似的东西？
EDIT: after answers, retainAll() is the right method. Thank you. Here is the source:
编辑：回答后，retainAll() 是正确的方法。谢谢你。这是来源：
Set<Address> addressCross = scanList.get(0);
for (int i = 1; i < scanList.size(); i++) {
addressCross.retainAll(scanList.get(i));
}
for (Address address : addressCross) {
addresses.add(address);
}
采纳答案by Lavir the Whiolet
See "retainAll()".
请参阅“retainAll()”。
回答by Hyman
you can use retainAll(Collection<?> c), check it out here
你可以使用retainAll(Collection<?> c)，在这里查看
A side note: that operation is called intersection.
旁注：该操作称为交集。
To convert then it to a Listyou can use the method addAll(Collection<? extends E> c)which should work between all kinds of containers.
要将其转换为 aList您可以使用addAll(Collection<? extends E> c)应该在各种容器之间工作的方法。
eg:
例如：
ArrayList<Address> list = new ArrayList<Address>();
list.addAll(yourSet);
回答by ColinD
With Guava, you could do it like this:
使用Guava，你可以这样做：
Set<Address> intersection = scanList.get(0);
for (Set<Address> scan : scanList.subList(1, scanList.size())) {
intersection = Sets.intersection(intersection, scan);
}
List<Address> addresses = Lists.newArrayList(intersection);
This creates a view of the intersection of all the sets in the scanListand then copies the addresses in the intersection into a List. You would need to ensure your scanListhas at least one element in it, of course.
这将创建 中所有集合的交集的视图，然后将交集中scanList的地址复制到List. 当然，您需要确保scanList其中至少包含一个元素。
