反向排序HashMap? [英] sort HashMap in reverse?

问题描述

所以我碰到了这种方法，该方法能够按值对HashMaps进行排序.

So I came across this method which is able to sort HashMaps by value.

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
        return map.entrySet()
                .stream()
                .sorted(Map.Entry.comparingByValue())
                .collect(Collectors.toMap(
                        Map.Entry::getKey,
                        Map.Entry::getValue,
                        (e1, e2) -> e1,
                        LinkedHashMap::new
                        ));
    }

我想在Comparator上使用reversed()方法，但是我似乎找不到合适的放置位置.

I want to use the reversed() method on the Comparator but I can't seem to find the right place to put it.

推荐答案

应在comparingByValue()返回的Comparator上调用reversed()方法.不幸的是，Java的类型推断在这里分解，因此您必须指定通用类型:

The reversed() method should be called on the Comparator returned by comparingByValue(). Java's type inference breaks down here, unfortunately, so you'll have to specify the generic types:

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue
    (Map<K, V> map) {

    return map.entrySet()
            .stream()
            .sorted(Map.Entry.<K, V> comparingByValue().reversed())
            // Type here -----^ reversed() here -------^
            .collect(Collectors.toMap(
                    Map.Entry::getKey,
                    Map.Entry::getValue,
                    (e1, e2) -> e1,
                    LinkedHashMap::new
            ));
}

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