使用Collectors.toMap返回LinkedHashMap [英] Using Collectors.toMap to return a LinkedHashMap

问题描述

我该如何转换:

return this.subjects.entrySet()
            .stream()
            .collect(Collectors.toMap(e -> getArtistryCopy(e.getKey()), Map.Entry::getValue));

要返回LinkedHashMap而不是地图?

To return a LinkedHashMap instead of a map?

如果您需要知道， this.subjects 是 LinkedHashMap< AbstractArtistries，ArrayList< AbstractCommand>> .AbstractArtistry和command是我制作的两个自定义对象.我需要维持订单.

If you need to know, this.subjects is a LinkedHashMap<AbstractArtistries, ArrayList<AbstractCommand>>. AbstractArtistry and command are two custom objects I made. I need the order to be maintained.

getArtistryCopy()返回AbstractArtistry的副本(这是键).

getArtistryCopy() returns a copy of an AbstractArtistry (which is the key).

推荐答案

您可以使用

You can use the overload of Collectors.toMap that accepts a Supplier for the Map. It also takes a merge function that how to resolve collisions between duplicate keys.

return this.subjects.entrySet()
        .stream()
        .collect(Collectors.toMap(e -> getArtistryCopy(e.getKey()), 
                                  Map.Entry::getValue,
                                  (val1, val2) -> yourMergeResultHere,
                                  LinkedHashMap::new));

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