I’m quite new into programming and got a tricky question. I got an object which has multiple parameters: Every object always has non-null number attribute as well as one of three values-field. So for example, if valueOne is not null, the other two value fields valueTwo and valueThree would be null. So h…
Tag: java-stream
Using a predefined lambda as an argument in Java [closed]
Closed. This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 11 days ago. Improve this question So i’m trying to pass this test: I’m having a really hard time understanding how…
Retrieve word(s) from characters using map
I am trying to understand Collections and Stream. I have split the sentence below and kept the position of each letter (I ignored space/blank): “Hello Word!” Results: [H, e, l, l, o, , W, o, r, d, !] (charsList) {!=[10], r=[8], d=[9], e=[1], W=[6], H=[0], l=[2, 3], o=[4, 7]} (charsIndex) How can I…
List of BigDecimal: how to calculate absolute difference between elements not adjacent to Zero value using Java 8 Stream?
I have a list of BigDecimal that could be as elements: I would like to calculate the absolute difference between elements not next to Zero value, in this example difference between 3 and 4, 4 and 5. Expected result should be also of type List<BigDecimal>. Of course, the value of Zero could be in any pos…
Wildcard generic type of predicate in stream not applicable
I have a trimmed down version of my code to illustrate the issue. Here’s the compilation error I’m getting: My code: How would you fix the code to remove the error? Thank you! Answer The fact that you have applied instanceof check in the filter() doesn’t change the type of the stream, it rem…
Java-Stream – Grouping Lists based on several elements within each List
I have the following data stored as lists: I need to group it as follows What I have tried is the following: But this doesn’t give the desired result. Answer Here’s how you can apply nested groupingBy To collect it in the order encountered, you can use a LinkedHashMap, Result:
Java Stream – Collecting Parent-objects into a Set after applying flatMap()
Is it possible to go back to the parent-object after applying flatmap() operation, and accumulate parent-objects into a set? I have an UnifiedOfferEntity with set of other entity objects as a field: I would like to filter through fields of the parent-object (UnifiedOfferEntity) like this: And then I would lik…
Grouping by query results based on a date using stream API java
I have an entity object with several columns which looks like this: As I use a composite key I have an embeddable class I also have a repository class and I use several request. The following query allow to select database results based on a query on workflow value. String dates have the following format: 202…
Convert a List of JSON-objects input into a nested Map
I have a String input in the following format: Input String: [{ “id”:”1″, “name”:”A”, “address”:”St 1″},{ “id”:”2″, “name”:”B”, “address”:”St 2″}, …] And I want…
Java Stream GroupBy and Reduce
I have an Item class which contains a code, quantity and amount fields, and a list of items which may contain many items (with same code). I want to group the items by code and sum up their quantities and amounts. I was able to achieve half of it using stream’s groupingBy and reduce. The grouping by wor…