I was going through Streams Documentation and had observed that Stream is a typed interface that extends Base Stream with types as T and again Stream <T> How can a interface Stream can extend Base stream interface having type bounds just as the stream interface i.e. Stream <T>? Answer Why couldn&#…
Tag: java-stream
Creating a list of avalible Timeslots based on a list LocalDateTime objects and a List of taken Timeslots with Streams
I have a List<Timeslot> that contains entity Timeslot with the following fields: timeslot_id; day; start_time; end_time. For example, this list contains two records: start_time of the first record equals 9:00 and end_time equals 10:00. start_time of second object equals 10:00 and end_time equals 11:00. …
How can I use an If-statement inside the Collector?
The output I require is like this : The structure of this output is: Map<String, List<Pair<String, String>>> Where “Versions” is the key of the Map and [(“0.1″,”true”),(“0.2″,”false”),(“0.3″,”true”)] this is …
Does flatMap method only flattens the stream and not map it?
I see it’s written everywhere that flatMap flattens and map the stream but in practical for example in the below program using only flatMap we can’t perform mapping operation(changing it to uppercase). We need to separately use map method here. Is my understanding about flatMap wrong? Can anyone p…
How to add using element to a Collection Set using Streams?
Currently I am adding an element to a Collection Set like this. Is there a way to do this with Streams that does not use Stream.concat()? Answer I would suggest you to remodel the objects, you’re updating User’s favorites outside this should happen within the User class Read this OO Principle, Tel…
Sorting a List of Maps dynamically in Ascending and Descending order
I am having Maps inside a List. I need to sort the List based on the input dynamically by passing it as a parameter into the method sortData. It is working as expected, but the problem is that am not able to sort the list in reverse order. I’m getting an Error : The method get(String) is undefined for t…
Compilation error while merging two Maps is being issued for Map.Entry::getKey
Whenever I use Map.Entry::getKey in my streams for my public methods, I get an issue around my method not being static. I even tried making my method static, and it didn’t work. Below is the compile error I am getting from using Map.Entry()::getKey() : My code Answer The method arguments are of type Map…
Lists stream().map() no instance(s) of type variable(s) R exist so that Stream conforms to List
I am having a List of class Person. The Person class looks like this: Below is how I am declaring and initializing my List<Person>: What i want to achieve is to get a List<String> of all usernames using the Java Stream API, but not using for loop. Below is how I have tried to implement this: But I…
Mapping pair of elements into one with Stream IPA
So I’m wondering what is the best solution to the following problem: I have a list of items (a custom class) in a java collection ex Each item in the collection however has a corresponding logical pair also in the collection (so the pair’s are not necessarily following each other by index in the c…
Program Can’t sort Employee List [closed]
Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. This question was caused by a typo or a problem that can no longer be reproduced. While similar questions may be on-topic here, this one was resolved in a way less likely to help future readers. Closed 12 …