在 Java 8 中反转比较器

Reverse a comparator in Java 8(在 Java 8 中反转比较器)

问题描述

我有一个 ArrayList 并希望按降序对其进行排序.我使用 java.util.stream.Stream.sorted(Comparator) 方法.下面是根据 Java API 的描述:

I have an ArrayList and want sort it in descending order. I use for it java.util.stream.Stream.sorted(Comparator) method. Here is a description according Java API:

返回一个由该流的元素组成的流，根据提供的Comparator排序.

Returns a stream consisting of the elements of this stream, sorted according to the provided Comparator.

这个方法返回一个升序排序.我应该更改哪个参数，只是为了降序?

this methods return me a sort with ascending order. Which parameter should I change, just to have the descending order?

推荐答案

你可以使用Comparator.reverseOrder() 有一个比较器，提供与自然顺序相反的顺序.

You can use Comparator.reverseOrder() to have a comparator giving the reverse of the natural ordering.

如果要反转现有比较器的顺序，可以使用 Comparator.reversed().

If you want to reverse the ordering of an existing comparator, you can use Comparator.reversed().

示例代码:

Stream.of(1, 4, 2, 5)
    .sorted(Comparator.reverseOrder()); 
    // stream is now [5, 4, 2, 1]

Stream.of("foo", "test", "a")
    .sorted(Comparator.comparingInt(String::length).reversed()); 
    // stream is now [test, foo, a], sorted by descending length

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