Java-排序-变量比较器 [英] Java - Sort - Variable comparator

问题描述

我正在尝试根据用户输入对对象列表进行排序.我该如何使sort方法实现一个变体比较器?

I'm trying to sort a list of Objects based upon user input. How can I go about having the sort method implement a variant comparator?

示例:

List<S3ObjectSummary> objectSummaryList = getObjectSummaries();
objectSummaryList.sort(Comparator.comparing(S3ObjectSummary::getKey);

如何根据需要根据getKey/getModified/其他任意属性进行上述排序?

How can I make above sort based upon getKey / getModified / other arbitrary properties as required?

推荐答案

如果所有键"都将链接到getter方法，则可以在函数中使用键/getter的静态映射:

If all "keys" will be linked to getter methods, you can have a static mapping of key/getter that you use in a function:

注意:我们将不得不使用原始类型Comparable，因为我们不能使用不同的Functions<S3ObjectSummary, Comparable<T>>(即使所有吸气剂都将返回Comparable<X>对象，X也会有所不同)

Note: we'll have to use raw type Comparable as we can't use different Functions<S3ObjectSummary, Comparable<T>> (even if all getters will return Comparable<X> objects, X will vary)

Map<String, Function<S3ObjectSummary, Comparable>> map = new HashMap<>();
map.put("key", s3 -> s3.getKey());
map.put("modified", s3 -> s3.getModified());
// other entries

然后使用以下方法进行排序:

Then sort using:

objectSummaryList.sort(Comparator.comparing(map.get(compareByKey)));

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