将分组的可观测值的排放收集到一个列表中 [英] Collect grouped observables' emissions into one list

问题描述

我有以下用例(这当然是一个人为的例子，但是一旦我知道答案，我将能够将其移植到我要解决的实际问题中):

I have the following use case (this is of course a contrived example, but once I know the answer, I will be able to port it to a real problem I am to solve):

1. 获取整数列表.
2. 按 % 4 操作的结果对它们进行分组
3. 将每个组的元素收集到列表中
4. 忽略元素少于 3 个元素的任何组/列表
5. 发出单个列表，其元素是在步骤 #3 中创建的列表

这是我当前的代码:

    Observable
            .from(Arrays.asList(0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12))
            .groupBy(item -> item % 4)
            .subscribe(groupedObservable -> {
                groupedObservable
                        .toList()
                        .filter(list -> list.size() > 2)
                        .subscribe(result -> {
                            System.out.printf("%d results %s%n", result.size(), result);
                        });
            });

它的输出是:

4 results [0, 4, 8, 12]
3 results [2, 6, 10]
3 results [3, 7, 11]

所以它打印出每个组有多少个元素，然后是元素列表.我希望输出是(我实际上并不关心键):

So it prints out how many elements each group has and then the list of elements. I would like the output to be (I actually don't care about the keys):

3 个结果:[[0, 4, 8, 12], [2, 6, 10], [3, 7, 11]]

3 results: [[0, 4, 8, 12], [2, 6, 10], [3, 7, 11]]

即以某种方式将分组的 observable 压平到一个列表中.我没有这样做.例如，在 filter 之后添加 .flatMap(integers -> Observable.just(integers)) 不会改变任何东西，因为它只会影响每个分组的 observable，而不是整个流.有没有办法满足我的要求?

i.e. somehow flatten the grouped observables into one list. I fail to do so. For example, adding .flatMap(integers -> Observable.just(integers)) after the filter doesn't change anything, as it just influences each grouped observable, not the whole stream. Is there a way to fulfill my requirements?

推荐答案

我不确定我是否理解正确，但根据所需的输出，这里是您可能正在寻找的代码:

I'm not sure if I've understood you correctly, but based on the desired output here is the code you might be looking for:

public static void main(final String[] args) throws Exception {
    Observable.from(Arrays.asList(0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12))
            .groupBy(item -> item % 4)
            .flatMap(Observable::toList)
            .filter(integers -> integers.size() > 2)
            .toList()
            .subscribe(result -> {
                System.out.printf("%d results %s%n", result.size(), result);
            });
}

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