如何在 Rx 中的 groupBy 之后进行排序

Question

我在一项调查中得到以下回复。想法是按照受欢迎程度的顺序打印标题。因此，我将主题按标题分组，并按照受欢迎程度的顺序打印。我无法弄清楚如何在分组后对它们进行排序。感谢任何帮助。

我的代码

import com.google.common.collect.Maps;
import com.google.common.primitives.Ints;
import rx.Observable;

import java.io.IOException;
import java.nio.file.Paths;
import java.util.List;
import java.util.Map;

import static java.nio.file.Files.readAllLines;

public class FileProcess
{
    public static Map<Integer, String> LOOKUP = Maps.newConcurrentMap();

    static
    {
        LOOKUP.put(1, "Job Workflow for Connexus using Camel Activiti and the Oracle Grid Engine");
        LOOKUP.put(2, "Observe Don't Bake");
        LOOKUP.put(3, "Model Driven Development with EMF");
        LOOKUP.put(4, "Entity Resolution and Keying");
        LOOKUP.put(5, "Business Activity Monitoring");
        LOOKUP.put(6, "Scorecard Design 101");
        LOOKUP.put(7, "Introduction to Hadoop and Developing for Hadoop");
        LOOKUP.put(8, "Java 7 & 8 New Features");
        LOOKUP.put(9, "A tale of a leaking class loader");
        LOOKUP.put(10, "AOP usecases - Demonstration in.Net with Unity and Postsharp");
        LOOKUP.put(11, "Functional Programming with F#");
        LOOKUP.put(12, "UI Test Automation @ 0/year");
    }

    public static void main(String args[]) throws IOException
    {
        List<String> strings = readAllLines(Paths.get("C:/Users/p0c/Desktop/fav1.txt"));

        Observable.from(strings)
                .filter(line -> !line.endsWith("respondent's answers"))//ignore surveymonkey log
                .map(line -> replaceIndexWithTitle(line))//normalize
                .map(line -> removeIndexAsPrefix(line))//normalize
                .map(line -> line.toLowerCase())
                .groupBy(line -> line)
                .subscribe(observable ->
                                observable.count().subscribe(integer ->
                                                System.out.println(integer + "\t" + observable.getKey())
                                )
                );
    }

    private static String removeIndexAsPrefix(String line)
    {
        if (Character.isDigit(line.trim().charAt(0)))
        {
            return line.trim().substring(line.indexOf(".") + 1);
        }
        return line;
    }

    private static String replaceIndexWithTitle(String line)
    {
        if (Ints.tryParse(line.trim()) != null)
        {
            return LOOKUP.get(Ints.tryParse(line));
        }
        return line;
    }
}

当前输出

1   a tale of a leaking class loader
4   job workflow for connexus using camel, activiti and the oracle grid engine
1   observe don't bake
1   aop usecases - demonstration in .net with unity and postsharp
5   scorecard design 101
15  java 7 & 8 new features
1   job workflow for connexus using camel activiti and the oracle grid engine
16  introduction to hadoop and developing for hadoop
1   business activity monitoring
1   ui test automation @ 100/year
4   model driven development with emf
5   functional programming with f#
1   didn't attend
9   ui test automation @ 0/year
3   entity resolution and keying

示例响应

8
1/14/2015 4:54 PM View respondent's answers
Job Workflow for Connexus using Camel, Activiti and the Oracle Grid Engine
1/14/2015 4:10 PM View respondent's answers
Didn't attend
1/14/2015 11:21 AM View respondent's answers
Java 7 & 8 New Features
1/13/2015 1:17 PM View respondent's answers
functional programming with f#
1/13/2015 1:08 PM View respondent's answers
7.Introduction to Hadoop and Developing for Hadoop
1/13/2015 12:44 PM View respondent's answers
7
1/13/2015 11:11 AM View respondent's answers
6
1/13/2015 10:41 AM View respondent's answers
Java 7 & 8 New Features
1/13/2015 10:38 AM View respondent's answers
Java 7 & 8 New Features
1/13/2015 10:14 AM View respondent's answers
7
1/13/2015 9:56 AM View respondent's answers
UI Test Automation @ 0/year
1/13/2015 9:48 AM View respondent's answers
AOP usecases - Demonstration in .Net with Unity and Postsharp
1/13/2015 9:22 AM View respondent's answers
6.Scorecard Design 101
1/13/2015 9:17 AM View respondent's answers
6
1/13/2015 9:08 AM View respondent's answers
UI Test Automation @ 0/year
1/13/2015 9:06 AM View respondent's answers
4.Entity Resolution and Keying
1/13/2015 9:02 AM View respondent's answers
Java 7 & 8 New Features
1/13/2015 9:01 AM View respondent's answers
Job Workflow for Connexus using Camel, Activiti and the Oracle Grid Engine
1/13/2015 8:57 AM View respondent's answers
6
1/13/2015 8:55 AM View respondent's answers
Job Workflow for Connexus using Camel, Activiti and the Oracle Grid Engine
1/13/2015 8:54 AM View respondent's answers
Java 7 & 8 New Features
1/13/2015 8:54 AM View respondent's answers
7.Introduction to Hadoop and Developing for Hadoop
1/13/2015 8:48 AM View respondent's answers
8
1/13/2015 8:48 AM View respondent's answers
UI Test Automation @ 0/year
1/13/2015 8:47 AM View respondent's answers
6
1/13/2015 8:47 AM View respondent's answers
UI test automation @ 100/year
1/13/2015 8:44 AM View respondent's answers
Model Driven Development with EMF
1/13/2015 8:42 AM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/13/2015 8:42 AM View respondent's answers
12
1/13/2015 8:42 AM View respondent's answers
Java 7 & 8 New Features
1/13/2015 8:37 AM View respondent's answers
1
1/13/2015 7:40 AM View respondent's answers
UI Test Automation @ 0/year
1/12/2015 10:10 AM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/11/2015 9:34 AM View respondent's answers
1.Job Workflow for Connexus using Camel, Activiti and the Oracle Grid Engine
1/8/2015 5:07 PM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/8/2015 2:55 PM View respondent's answers
Java 7 & 8 New Features
1/8/2015 2:09 PM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/8/2015 1:36 PM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/8/2015 1:08 PM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/8/2015 1:02 PM View respondent's answers
UI Test Automation @ 0/year
1/8/2015 12:44 PM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/8/2015 12:31 PM View respondent's answers
UI Test Automation @ 0/year
1/8/2015 12:21 PM View respondent's answers
12.UI Test Automation @ 0/year
1/8/2015 12:04 PM View respondent's answers
8
1/8/2015 12:01 PM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/8/2015 11:58 AM View respondent's answers
Java 7 & 8 New Features
1/8/2015 11:56 AM View respondent's answers
4.Entity Resolution and Keying
1/8/2015 11:56 AM View respondent's answers
7
1/8/2015 11:53 AM View respondent's answers
Model Driven Development with EMF
1/8/2015 11:51 AM View respondent's answers
Introduction to Hadoop and Developing for Hadoop
1/6/2015 11:54 AM View respondent's answers
Java 7 & 8 New Features
1/5/2015 1:14 PM View respondent's answers
3.Model Driven Development with EMF
1/5/2015 11:55 AM View respondent's answers
11.Functional Programming with F#
1/5/2015 11:50 AM View respondent's answers
Java 7 & 8 New Features
1/5/2015 11:44 AM View respondent's answers
Entity Resolution and Keying
1/5/2015 10:26 AM View respondent's answers
Model Driven Development with EMF
1/5/2015 9:54 AM View respondent's answers
11
1/5/2015 9:24 AM View respondent's answers
11
1/5/2015 9:11 AM View respondent's answers
8
1/5/2015 8:44 AM View respondent's answers
7
1/5/2015 8:13 AM View respondent's answers
11
1/5/2015 8:11 AM View respondent's answers
UI Test Automation @ 0/year
1/5/2015 7:22 AM View respondent's answers
7
1/4/2015 4:46 PM View respondent's answers
9
1/4/2015 3:24 PM View respondent's answers
Business Activity Monitoring
1/4/2015 9:43 AM View respondent's answers
Java 7 & 8 New Features
1/3/2015 9:38 PM View respondent's answers
Observe Don't Bake
1/3/2015 3:32 PM View respondent's answers

Answer 1

在 .NET 中，如果它是有限序列，您通常会使用 GroupByUntil 或 GroupBy，并且只需将 ToList 应用于每个组。然后只需交互式排序。我怀疑它在 RxJava.

中是一样的

原因是基于反应数据的排序没有意义。在拥有整个列表之前，您无法对列表进行排序，这意味着您需要 OnCompleted。如果您正在寻找部分排序，那么您可以使用 GroupByUntil 如上所述， until 部分可以定义部分排序边界。

注意，我做出了a PR for a complete set of OrderBy operators in Rx.NET，在上述前提下被审核拒绝了。我在 Twitter 上也与 Erik Meijer 就这个主题进行了简短的讨论，他基本上说服了我，像 OrderBy 这样的有限序列运算符不属于 Rx。我能够确定使用它的潜在性能原因，但最终我无法证明其使用的合理性。

附录：

我想补充一点，如果您的示例显示了您实际使用 Rx 的方式，那么我认为您一开始就不应该在这里使用 Rx。 Rx 用于响应式数据处理，但您只是在处理内存中的列表。在 .NET 中，我们会改用 LINQ to Objects，但我不知道 Java.

中是否有任何等效项

如何在 Rx 中的 groupBy 之后进行排序

How to sort after a groupBy in Rx

system.reactive

reactive-programming

rx-java