使用Collections.frequency（）打印某些值 [英] Printing certain values using Collections.frequency()

问题描述

我有一个如下数组：

int[] array = {11, 14, 17, 11, 48, 33, 29, 11, 17, 22, 11, 48, 18};

我想要做的是找到重复的值，并打印出来。

What I wanted to do was to find the duplicate values, and print them.

所以我的方法是转换为 ArrayList ，然后转换为 Set 并在集上使用流。

So my way of doing this was to convert to ArrayList, then to Set and use a stream on the Set.

ArrayList<Integer> list = new ArrayList<>(array.length);
for (int i = 0; i < array.length; i++) {
    list.add(array[i]);
}

Set<Integer> dup = new HashSet<>(list);

然后我使用流来循环它并使用 Collections.frequency 打印值。

I then used a stream to loop through it and print the values using Collections.frequency.

dup.stream().forEach((key) -> {
            System.out.println(key + ": " + Collections.frequency(list, key));
        });

当然，即使计数为1，也会将它们全部打印出来。

Which will of course print them all, even if the count is one.

我想在中添加if（key> 1），但这是我想要的值而不是密钥。

I thought adding in if(key > 1) but it's the value I want not the key.

如何才能使此实例中的值仅在值>的位置打印2 。

How can I get the value in this instance to print only where value > 2.

我可以投入：

int check = Collections.frequency(list, key);
            if (check > 1) {

但这会重复 流中的Collections.frequency（列表，密钥），并且非常丑陋。

but this then duplicates Collections.frequency(list, key) in the stream and is quite ugly.

推荐答案

可能你可以使用过滤器来获得大于2的值：

Probably you can to use filter to get only the values great than 2 :

dup.stream()
       .filter(t -> Collections.frequency(list, t) > 2)
       .forEach(key -> System.out.println(key + ": " + Collections.frequency(list, key)));

结果你的情况是：

11: 4

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编辑

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Edit

另一个解决方案：

无需使用 Set 或 Collections.frequency 您可以使用：

No need to use a Set or Collections.frequency you can just use :

Integer[] array = {11, 14, 17, 11, 48, 33, 29, 11, 17, 22, 11, 48, 18};
Arrays.stream(array).collect(Collectors.groupingBy(p -> p, Collectors.counting()))
        .entrySet().stream().filter(t -> t.getValue() > 1)
        .forEach(key -> System.out.println(key.getKey() + ": " + key.getValue()));

输出

48: 2
17: 2
11: 4

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