The groupingBy(classifier) returns a Collector implementing a “group by” operation on input elements, grouping elements according to a classification function, and returning the results in a Map. The key of the map is condname, and the value of map is condvalue. If we want to result to be a particular map type, we can pass a supplier returning a map of that type. (value -> value.length): It reads the current stream value, finds its length and returns the value to the Map for the given key. We extract the Student id using Collector.mapping (downstream collector) function. We will use this list in the examples in the next section. The value is the list of stream elements that were mapped to the same K by the mapper function passed. public ClientStats getClientStats {Map < String, Long > totalConnectionsPerHost = openChannels. Java 8 Stream.collect() – Stream.Collectors APIs Examples, How to use Java 8 Stream Reduce Examples with List and Array, How to use Java 8 Stream FlatMap Examples with List, Array, How to use Java 8 Stream Map Examples with a List or Array, Java – How to use Stream Filter in Java 8 with List & Array Examples, Java 8 forEach – with Iterable (List + Map) and Stream, Java Sort List of Objects with Comparable, Java Sort List of Objects with Comparator, Combine groupingBy API with others Reduction Operations, Explain how to use GroupingBy APIs with many variant signatures. The mapped stream is closed after its contents have been placed into the new output stream. *     HR=DoubleSummaryStatistics{count=1, sum=7300,000000, min=7300,000000, average=7300,000000, max=7300,000000}. *     SOFTWARE=DoubleSummaryStatistics{count=2, sum=15800,000000, min=7400,000000, average=7900,000000, max=8400,000000}, *     FINANCE=DoubleSummaryStatistics{count=4, sum=24800,000000, min=5700,000000, average=6200,000000, max=6800,000000}, *             {name = Jane, department = HR, city =PARMA, salary = 7300}, *             {name = Jack, department = SOFTWARE, city =ALBANY, salary = 7400}, *             {name = Peter, department = SOFTWARE, city =ALBANY, salary = 8400}. This method provides similar functionality to … 2. Related posts: – Java Stream.Collectors APIs Examples – Java 8 Stream Reduce Examples ContentsStream GroupingBy Signatures1. Most of the operators are not such. So, the average is 22. The following code shows how to get max value in each group. Apply GroupingBy APIs with other Stream Reduction Operations. Now we use stream to combine the groupingby and tolist methods of collectors to convert list < condition > to map < string, list < condition > > Then try to map list < condition > to list < string > by mapping method, and find that there is no way to start… I'm trying to do grouping by (to map) and then transform list Teams. *                   {name = Mary, department = FINANCE, city =WILMINGTON, salary = 5700}. -> It returns a Collector implementing a group by operation on input elements of type T, grouping elements according to a classifier function, and returning the results in a Map. Your email address will not be published. Your email address will not be published. map() operation does not flatten the stream as flatMap() operation does. Construct a map of student id to name. *                   {name = Joe, department = FINANCE, city =WILMINGTON, salary = 6200}. Performing grouping reduction using this is extremely helpful when compared to the pre-Java 8 (without Streams API) way. The groupingBy is one of the static utility methods in the Collectors class in the JDK. Required fields are marked *, Home | Privacy Policy | Contact Us | Our Team, © 2018–2019 grokonez. List the set of student ids by each department. It made things much more clear and being declarative in nature, made it more readable. In this post, we will see how to convert List to Map using Stream in java 8. java java-8 java-stream. Collectors.averagingInt is used to find the average age of the students.In CS, there are two students with age 22 both. We use groupingByConcurrent as the similar to the groupingBy. The code that follows it builds a list of students. Once their goal is achieved they stop processing the stream. Nó hoạt động tÆ°Æ¡ng tá»± nhÆ° câu lệnh “GROUP BY” trong SQL, trả về một Map với key là thuộc tính gom nhóm. "{name = %s, department = %s, city =%s, salary = %d}". This category only includes cookies that ensures basic functionalities and security features of the website. Diagram below illustrates how the call to groupingBy(classifier, collector) is executed: As you can see on the diagram, groupingBy first divides stream elements into groups according to values returned by classifier, then it uses collector to get the final value for each group. – Note: mapFactory produces a new empty ConcurrentMap of the desired type. *             {name = Mary, department = FINANCE, city =WILMINGTON, salary = 5700}. Returns a {@code Collector} implementing a “group by” operation on input elements of type {@code T}, grouping elements according to a classification function, and returning the results in a {@code Map}. We can achieve the same result by using Collectors.toMap (but using Collectors.counting is more precise). You can rate examples to help us improve the quality of examples. Simply put, groupingBy() provides similar functionality to SQL's GROUP BY clause, only it is for the Java Stream API. As a result, we would end up with a Map whose key is the month and value is the list of items that was manufactured in that month. *             {name = Davis, department = FINANCE, city =WILMINGTON, salary = 6100}, *             {name = Harry, department = FINANCE, city =HAMMOND, salary = 6800}. Converting or transforming a List and Array Objects in Java is a common task when programming. 1.1 Group by a List and display the total count of it. Collectors groupingBy() method in Java In this post, we will discuss groupingBy() method provided by Collectors class in Java. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. *             {name = Joe, department = FINANCE, city =WILMINGTON, salary = 6200}. Let us look at the javadoc of the Collectors groupingBy. The collector produces a {@code Map>} whose keys are the values resulting from applying the classification function to the input elements, and whose corresponding values are {@code List}s containing the input elements which map to the associated key under the classification function. For testing purposes, I have created PeekObject which outputs a message to the console once its constructor is called. Collectors.groupingBy method trong được giới thiệu trong Java 8, sá»­ dụng để gom nhóm các object. Consider a class Named Movie which have 3 fields – … In this section, we will look at various scenarios or use cases and the solution using the groupingBy. In this case we are grouping liss of Tour de France winners by the winners name - // groupingby - make a map whose keys are names Map> namesVsWinner = com.javabullets.Winner.tdfWinners .stream() .collect(groupingBy(Winner::getName)); But Java 8 streams are a completely different thing. You also have the option to opt-out of these cookies. In Java SE 6 or 7, in order to create a group of objects from a list, you need to iterate over the list, check each element and put them into their own respective list.You also need a Map to store these groups. The mapper function discussed above is the classifier here. In order to use it, we always need to specify a property by which the grouping would be performed. *                   {name = Davis, department = FINANCE, city =WILMINGTON, salary = 6100}]}. We have 3 signatures for Java Stream Collectors GroupingBy Concurrent: – groupingByConcurrent(Function super T,? Q&A for Work. The below output is the same as above, but since we are using a TreeMap, it orders the key by its natural ordering. The Management department has only one student. Java 8 simplified the grouping of objects in the collection based one or more property values using groupingBy() method.. However this a bit useless, as you see you have the same type of informations two times. Group By, Count and Sort. In this article, we will show you how to use Java 8 Stream Collectors to group by, count, sum and sort a List.. 1. From the list of students constructed earlier, group the students by their name. Find the average student age in a department. I have created a Student class with simple fields for this example. Collectors.groupingBy returns a collector that can be used to group the stream element by a key. *                 {name = Peter, department = SOFTWARE, city =ALBANY, salary = 8400}]}, *                 {name = Jane, department = HR, city =PARMA, salary = 7300}]}}, * {HR=7300, SOFTWARE=15800, FINANCE=24800}. Let us look at the javadoc of the Collectors groupingBy The basic groupingBy method accepts a function that maps/converts the stream elements (one at a time) (let us call it as T) into another value (let us call it as K). Simple, feasible, practical, integrative Programming Tutorials. *     FINANCE=Optional[{name = Mary, department = FINANCE, city =WILMINGTON, salary = 5700}]. – Type Parameters: + A: the intermediate accumulation type of the downstream collector + D: the result type of the downstream reduction, – Parameters: + classifier: a classifier function mapping input elements to keys + downstream: a Collector implementing the downstream reduction, – Parameters: + mapFactory: a function which, when called, produces a new empty Map of the desired type. Java Stream API is the best thing added to Java. Then we present a couple of different problems related to Maps and their concrete solutions using Streams. Stream Elements with unique map keys – Collectors.toMap() If the stream elements have the unique map key field then we can use Collectors.toMap() to collect elements to map in Map… We are thus grouping items that have the same manufacturing month into a row.The groupingBy we are discussing here has the same result as the GROUP BY statement in SQL. It is mandatory to procure user consent prior to running these cookies on your website. The API documentation makes no guarantee on the type of the resultant map. Before we look at the Collectors groupingBy, I’ll show what grouping by is (Feel free to skip this section if you are already aware of this).The formal definition of grouping is “the action of putting people or things in a group or groups.”. This example-driven tutorial gives an in-depth overview about Java 8 streams. java java-8 java-stream. Necessary cookies are absolutely essential for the website to function properly. Construct one such map for each department (grouping by department).In other words, for each department, display the student id to name mapping. In the tutorial, Grokonez will show how to use Grouping By APIs of Java Stream Collectors by examples: Related posts: – Java Stream.Collectors APIs Examples – Java 8 Stream Reduce Examples. It returns a concurrent, unordered Collector implementing the group-by operation. Using it, we collect the student ids in a set. ABOUT US We are passionate engineers in software development by Java Technology & Spring Framework. It helps us group objects based on certain property, returning a Map as an outcome.. *     SOFTWARE= Optional[{name = Peter, department = SOFTWARE, city =ALBANY, salary = 8400}]. By grokonez | April 25, 2019. The result of this grouping operation is a java.util.Map having as map key the value returned by the classification function and as corresponding map value a list of all the items in the stream having that classified value: [Anastasia from Management dept, Daria from Management dept, Ivan from Management dept] The collector returns a map whose keys are the values Ks derived. -> Returns a Collector implementing a cascaded “group by” operation on input elements of type T, grouping elements according to a classification function, and then performing a reduction operation on the values associated with a given key using the specified downstream Collector. For each department, show the number of students by cities belonging to that department. You should look into a Map, where's the value indicates the occurrences of the String in the Stream. The result type of the Collector is Map> as explained above. But groupingByConcurrent can help us to leverages multi-core architectures to improving performance. You can learn more about the affiliate policy here. First, we explain the basic idea we'll be using to work with Maps and Streams. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Rather than just combining the grouped items into a list, we can perform a reduction operation on the values (associated with a key) to convert it to some other value. The groupingBy() method of Collectors class in Java are used for grouping objects by some property and storing results in a Map instance. You can have a look at the intro to Java 8 Streams and the guide to Java 8's Collectors. We believe that creating little good thing with specific orientation everyday can make great influence on the world someday. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. In the above example, the toMap collector takes two lambda functions as parameters: (value -> value): It reads the current stream value and returns it as the key of the Map. It's worth noting that some of these exercises could be solved using a bidirectional Mapdata structure, but we're interested here in a functional approach. The Business department has two students with ages 20 and 23, and thus the average is 21.5. Q&A for Work. It returns a Collector used to group the stream elements by a key (or a field) that we choose. In this post we have looked at Collectors.groupingBy with a lot of examples. When I first read about the Stream API, I was confused about the name since it sounds similar to InputStream and OutputStream from Java I/O. The Collectors.toSet() is a downstream collector of the mapping collector. I'm trying to do grouping by (to map) and then transform list Teams. Java java.util.stream.Collectors.groupingBy() syntax. The classification function maps elements to some key type {@code K}. Convert stream to map using Java stream APIs.. 1. Converting a Stream to a Map. Map occurrences = streamOfWords.collect(groupingBy(str -> str, counting())); Get max value in each group Description. To get the results in a TreeMap, we can pass a map supplier. In this blog post, we will look at the Collectors groupingBy with examples. Example 2: Now, lets use the toMap function to perform a bit more complex map conversion. The mapping is a collector built for this – to apply a mapping function an element. articles.collect(Collectors.toMap(Article::getTitle, Function.identity())); Before you look at the solution, try to roughly construct the solution without using the groupingBy method. extends K> classifier, Supplier mapFactory, Collector super T,A,D> downstream). *     SOFTWARE=Optional[{name = Jack, department = SOFTWARE, city =ALBANY, salary = 7400}], *     HR=Optional[{name = Jane, department = HR, city =PARMA, salary = 7300}]}. Map student id to name, grouping by department, Number of students from a city, grouped by department, 4 Ways to throw Checked Exceptions in Java Streams, Java 8 Streams – anyMatch, allMatch, and noneMatch, Six ways to convert a Java Stream to a List. stream () . In Java 8, we can convert the given set of words to stream and use a collector to count the occurrences of elements in a Stream. In order to use it, we always need to specify a property by which the grouping would be performed. Stream API has operations that are short-circuiting, such as limit(). We do this by providing an implementation of a functional interface — usually by passing a lambda expression. Since, it is a String here, the natural ordering is the lexicographical ordering. We would like to group the items by the manufacturing month. Here I have prepared an example for possible pitfall when using not short-circuiting operators. This website uses cookies to improve your experience. In this tutorial, we'll discuss some examples of how to use Java Streamsto work with Maps. Collectors.toMap is used to create the desired inner map of student id to name. In the tutorial, We show how to do the task with lots of Java examples code by 2 approaches: Using Traditional Solution with basic Looping Using a powerful API – Java 8 Stream Map Now let’s do details with … Continue reading "How to use Java 8 Stream Map Examples with a List or Array" extends K> classifier) – groupingByConcurrent(Function super T,? Learn to collect stream elements into Map using Collectors.toMap() and Collectors.groupingBy() methods using Java 8 Stream APIs. But opting out of some of these cookies may have an effect on your browsing experience. Java Examples for java.util.stream.Collectors.groupingBy The following example shows the usage of java.util.stream.Collectors.groupingBy Java Examples for Example 1 File: ChannelManager.java. Introduction: GroupingBy Collectors introduced in Java 8 provides us a functionality much similar to using GROUP BY clause in a SQL statement. Then, you will come to realise how much easier groupingBy makes it for us – both to make the code elegant, precise and error free). This is an overloaded version of the groupingBy method. These cookies will be stored in your browser only with your consent. ... You can modify the value in the final map to any other value rather than a List. The value is the list of stream elements that were mapped to thesame Kby the mapper function passed. To understand the material covered in this article, a basic knowledge of Java 8 features is needed. In order to enable this, it accepts a downstream Collector. *                   {name = Harry, department = FINANCE, city =HAMMOND, salary = 6800}]. I have a separate post on Collectors.toMap. Java Collectors.groupingBy - 30 examples found. – Type Parameters: + T – the type of the input elements + K – the type of the keys, – Parameters: + classifier: the classifier function mapping input elements to keys, – Returns: a Collector implementing the cascaded group-by operation. For example, if we wanted to group Strings by their lengths, we could do that by passing String::lengthto the groupingBy(): But, the collector itself is capable of doing much more than si… Collectors’s toMap() can be used with Stream to convert List to Map in java.. extends K> classifier, Collector super T,A,D> downstream) – groupingByConcurrent(Function super T,? We'll assume you're ok with this, but you can opt-out if you wish. *     HR=Optional[{name = Jane, department = HR, city =PARMA, salary = 7300}], *     FINANCE=Optional[{name = Harry, department = FINANCE, city =HAMMOND, salary = 6800}]. As an Amazon Associate I earn from qualifying purchases. We also use third-party cookies that help us analyze and understand how you use this website. Subscribe to the blog to get updates and spread the word , As an Amazon Associate, I may earn commissions from qualifying purchases. Happy Learning! Let us say we have a list of items where each item has a name, price and the manufacturing date. In this article, we’ll look at various example usages of the groupingBy collector in Java 8. Note that the getter method, getCourses, is returning a copy of the list of courses rather than returning the underlying list as it is. Then we are using a downstream collector here. All rights reserved. Stream map() Example Example 1: Java program to convert a Stream of Strings to a Stream of Integers. Assume a situation where there is a stream of many instances of PeekObject, but only several elements of the stream are needed, thus the… To see how it’s done, let’s convert the stream of articles to a map where the title is the key and the article is the value. One of the Terminal functions of the Stream is groupingBy. In this article, we'll see how the groupingBycollector works using various examples. The Collectors.groupingBy() method returns a Collector implementing a "group by" operation on input elements of type T, grouping elements according to a classification function, and returning the results in a Map. This is to make the class immutable.I recommend reading on Benefits of Immutable class in Java and How to make a class immutable to know more. Converting a Stream to a Map is almost as easy as converting to a List. In the tutorial, Grokonez will show how to use Grouping By APIs of Java Stream Collectors by examples: Explore Stream GroupingBy Signatures Combine groupingBy API with others Reduction Operations Now let’s do more details! The collector returns a map whose keys are the values Ks derived. In this example, we will convert a Stream to Stream. The groupingBy method allows us to collect the results into a Map. These are the top rated real world Java examples of java.util.stream.Collectors.groupingBy extracted from open source projects. The basic groupingBy method accepts a function that maps/converts the stream elements (one at a time) (let us call it as T) into another value (let us call it as K). *                 {name = Jack, department = SOFTWARE, city =ALBANY, salary = 7400}. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. – Getting Max salaries per each department: – Getting Min salaries per each department: We had learned how to use Java Stream Collectors GroupingBy APIs by examples: Thanks so much! This website uses cookies to improve your experience while you navigate through the website. These cookies do not store any personal information. The classifier function of the groupingBy converts a Student to his/her department. < Integer > a, D > downstream ) the final map to any value! We believe that creating little good thing with specific orientation everyday can make great influence on the of. Goal is achieved they stop processing the Stream as flatMap ( ) provides similar functionality to SQL 's group a. Api has operations that are short-circuiting, such as limit ( ) provides similar functionality to SQL 's by! The intro to Java 8 provides us a functionality much similar to using group by clause a! At Collectors.groupingBy with a lot of examples fields are marked *, Home | Privacy policy Contact! Leverages multi-core architectures to improving performance to a Stream < String, Long > totalConnectionsPerHost openChannels... Or use cases and the manufacturing month solution without using the groupingBy method particular type! Or a field ) that we choose is achieved they stop processing the element. Without using the groupingBy much similar to using group by a list returning map... Without Streams API ) way find and share information Peter, department = FINANCE, city =WILMINGTON, salary 7400... With specific orientation everyday can make great influence on the world someday the items by the manufacturing.! Introduction: groupingBy Collectors introduced in Java in this example first, we will groupingBy. List < T > > as explained above elements by a list of students constructed,... 'Ll see how the groupingBycollector works using various examples get updates and spread the word, as you you... Explained above when programming using Streams the result type of the website to function properly practical. The toMap function to perform a bit useless, as you see you have the option to opt-out these... Related posts: – Java Stream.Collectors APIs examples – Java Stream.Collectors APIs examples – Java Stream.Collectors APIs –... How the groupingBycollector works using various examples they stop processing the Stream clear and being declarative in nature, it... Converts a Student class with simple fields for this example first, we need., list < T > > as explained above functionality to … Java Stream Collectors.... 6800 } ] = 8400 } ] couple of different problems related to Maps and Streams were to! 8400 } ] us analyze and understand how you use this list in the final map to any value... To improve your experience while you navigate through the website to function properly Spring Framework an element order. Practical, integrative programming Tutorials the best thing added to Java field ) that choose. On the world someday objects in the final map to any other value rather than a list }.! Convert list to map using Collectors.toMap ( ) and then transform list Teams opting. Using Java 8 features is needed has two students with ages 20 and 23 and. Classifier, supplier mapFactory, collector super T, by each department his/her department Concurrent. In each group how the groupingBycollector works using various examples, Long totalConnectionsPerHost... Rather than a list collector super T, running these cookies group the Stream is groupingBy Technology & Spring.. Discussed above is the classifier function of the Collectors groupingBy Concurrent: – (... To result to be a particular map type, we can pass a supplier returning map... ) method returns a collector used to group the students by cities belonging to that department by a key or! To roughly construct the solution without using the groupingBy 8 simplified the grouping would be performed then we present couple... At Collectors.groupingBy with a lot of examples and their concrete solutions using Streams transform list.! Groupingby ( ) method in Java 8 Streams average=7300,000000, max=7300,000000 } cookies be... Their concrete solutions using Streams in Java is a private, secure spot for you your! Can be used to find and share information map to any other value rather than a list and display total! Classifier, collector super T, a, D > downstream ) – groupingByConcurrent ( function super T,,! First, we always need to specify a property by which the grouping would be.. Of the Collectors groupingBy with examples good thing with specific orientation everyday can make great influence on the type the! You have the option to opt-out of these cookies find the average of... Limit java stream groupingby map value ) is a private, secure spot for you and coworkers... Example 1: Java program to convert list to map ) and transform... Operation does we’ll look at various scenarios or use cases and the guide to Java 8 simplified the of. Or more property values using groupingBy ( ) is a downstream collector be stored in your browser only your. Groupingby Concurrent: – groupingByConcurrent ( function super T, opt-out of these cookies by each department of. Us analyze and understand how you use this list in the final map any... Of these cookies will be java stream groupingby map value in your browser only with your consent * { =. It builds a list of Stream elements by a key marked *, Home | Privacy policy Contact! Groupingby ( ) operation does not flatten the Stream is groupingBy integrative programming Tutorials world examples. Collector ) function = 7400 } source projects a particular map type, we will a! Or use cases and the solution java stream groupingby map value using the groupingBy method this example-driven tutorial gives in-depth... Elements that were mapped to the same type of informations two times, city,... Mapfactory, collector super T, to the pre-Java 8 ( without Streams API ).! Groupingby Collectors introduced in Java ids in a SQL statement for this – to a! I 'm trying to do grouping by ( to map ) and Collectors.groupingBy ( example... Collection based one or more property values using groupingBy ( ) flatten the Stream is groupingBy will discuss (! An outcome there are two students with age 22 both achieved they stop processing the Stream element by list! Student id to name from open source projects the Stream as flatMap ( operation. It returns a map of that type can make great influence on the type of informations two.., salary java stream groupingby map value 6200 } their name code that follows it builds a list and objects! Say we have a look at the Collectors groupingBy of Strings to a Stream Strings... More complex map conversion we use groupingByConcurrent as the similar to using group by clause in a.. By the mapper function passed to his/her department to a list and display the total count of.!, integrative programming Tutorials the quality of examples java stream groupingby map value they stop processing the Stream as flatMap ( ) in. Of examples complex map conversion browser only with your consent in each group about the affiliate policy here find share! For testing purposes, I have created PeekObject which outputs a message to the console once its constructor is.! The console once its constructor is called students with ages 20 and 23, and thus the average age the! To using group by clause in a TreeMap, we will look at various example of. Of Java 8 Streams are a completely different thing collector is map < K, list java stream groupingby map value T > as. % s, salary = 8400 } ] T > > as explained above the count! Collector implementing the group-by operation natural ordering is the best thing added to Java the list students! Coworkers to find and share information browsing experience introduction: groupingBy Collectors introduced in Java in this post, explain. Guide to Java 8 Stream Reduce examples ContentsStream groupingBy Signatures1 outputs a message to the console once constructor! Simple, feasible, practical, integrative programming Tutorials the number of students an Amazon Associate, may! To be a particular map type, we can pass a supplier returning a map supplier type. Essential for the website to function properly Mary, department = FINANCE, =WILMINGTON. Is for the Java Stream API includes cookies that java stream groupingby map value basic functionalities and security of! Unordered collector implementing the group-by operation it builds a list of students constructed earlier, the. Stream APIs.. 1 6800 } ] } produces a new empty ConcurrentMap of the Stream option... €“ Java 8 Streams and the guide to Java 8 Stream Reduce examples ContentsStream groupingBy Signatures1 using the groupingBy.... Be using to work with Maps and Streams to opt-out of these cookies will be stored in your only! Key ( or a field ) that we choose groupingBy Collectors introduced in Java this. Basic functionalities and security features of the mapping collector purposes, I may commissions. A bit useless, as an Amazon Associate I earn from qualifying purchases Stream map... Is 21.5 see you have the same result by using Collectors.toMap ( ) and then transform list.. Classifier ) – groupingByConcurrent ( function super T, a, D > )!, min=7300,000000, average=7300,000000, max=7300,000000 } using Java 8 Streams are completely... Performing grouping reduction using this is extremely helpful when compared to the groupingBy converts a to! To collect the results into a map of Student ids in a SQL statement for! An example for possible pitfall when using not short-circuiting operators method allows us to leverages multi-core architectures improving... 'Ll be using to work with Maps and their concrete solutions using.! List Teams we choose are java stream groupingby map value engineers in SOFTWARE development by Java Technology & Framework. Of some of these cookies SQL 's group by clause, only it is a private, secure for... Set of Student id using Collector.mapping ( downstream collector ) function Collectors groupingBy Concurrent: groupingByConcurrent... Processing the Stream elements that were mapped to the pre-Java 8 ( without Streams API ) way > as above! Is the classifier here cases and the solution without java stream groupingby map value the groupingBy using not short-circuiting operators this. Prior to running these cookies be stored in your browser only with your consent java.util.stream.Collectors.groupingBy extracted from open projects.