12,129 questions
2
votes
1
answer
74
views
How to use groupby collectors while modifying the values
I'm preparing for a test and in preparation I was looking at this question, which I want to rewrite in the stream / collector way.
The assignment is a wooden plank with nails hammered in. The nails ...
- 10.1k
0
votes
1
answer
43
views
Iterating a list once instead of twice
I have a json for students with marks . I need to get the total marks for maths and english per standard . I could do it for each subject like below , but here the list is iterated twice. Is there a ...
- 327
2
votes
1
answer
70
views
Java Stream API: Incompatible types: List<ArrayList>> cannot be converted to List<List>
My intention was to replace the following snippet:
List<List<String>> lists;
for (int i = 0; i < n; i++)
lists.add(new ArrayList<String>());
with Stream API one-liner:
List&...
- 41
0
votes
1
answer
34
views
Grouping By Child Class into Map
I had made a list of Parent Class (as Employee) having a parameter of child class (as Department)
class Employee {
Integer empId;
String empName;
Long salary;
String email;
...
- 2,256
0
votes
1
answer
119
views
Compiling Stream Gatherers / jdk24 features
I don't know how to fix this error: (I use IntelliJ IDEA 2024.2.5 (Community Edition)
java: invalid source release 23 with --enable-preview
(preview language features are only supported for release ...
3
votes
2
answers
159
views
Collectors#toMap: No NPEs on null values
What if I don't want Collectors#toMap to throw on null values? Java 8
public class CollectorsTest {
@Test
public void collectorsTest() {
List<Map.Entry<String, Object>> ...
- 1,897
0
votes
0
answers
62
views
Is there elegant way to fork and join Java streams?
I have quite simple task: there is a List<Map> exposed from unsorted YAMLs and JSONs. I need to filter the list to find some particular data structures and extract some part of them -- four ...
- 383
1
vote
1
answer
61
views
Create a list of data carriers with java Streams
I want to convert a list of nested objects into a flat list using Java streams.
For this reason, a list of companies is first drawn up with employees:
// create Apple Employees
List<...
- 43
2
votes
1
answer
66
views
JwkSet gives Cannot resolve constructor 'JWKSet(List<RSAKey>)' - Stream.collect(Collectors.toList()) vs Stream.toList()
In our code, we use JWKset from the nimbus-jose-jwt library in a method that creates a map that we use for stuff. As you can see in the return, we use a stream that calls map on a list of RSAkey, and ...
1
vote
0
answers
50
views
Lazy de-serialization of a JSON array as a Stream<T> [duplicate]
Consider I have a large (potentially infinite) array of JSON objects:
[
{
"id": 41,
"name": "foo"
},
{
"id": 42,
&...
- 5,368
2
votes
3
answers
229
views
How to sort a list of object by two fields when the first field is a date but of string type and the second field is a plain string
I have an array of Object that I need sorted by two of the object's fields.
Product.java
private String productionDate;
private String productionCountry;
private String productDescription;
Now I ...
- 1,067
0
votes
2
answers
95
views
Object attribute always evaluates to not-null in a java streams map() transformation even though it is null in some cases
So say, I have a class:
public class Clazz {
final String someAttribute;
public String getSomeAttribute() {
return someAttribute;
}
public void setSomeAttribute(String ...
-4
votes
1
answer
100
views
How can I inflate entry stream?
With given map,
Map.of(
"A", 5,
"C", 13,
"E", 2,
"M", 5,
"T", 45,
"W", 2
);
How can I ...
- 22.1k
-1
votes
2
answers
98
views
ArrayList filled with parallel stream contains null values and leaves some out [closed]
I am trying to fill an Arraylist, as there are usually very large values I have decided to parallelize it with ExecutorService and CompletableFuture and later with parallel stream, but in both cases,...
- 21
-7
votes
1
answer
68
views
Need to group by list of list in pojo in java and sort by year and month
We are getting list of AssetValue from database,
After getting the list I need to group by id and sort by year and month.
Based on the grouping I need to print on reports.
Public Class AssestValue{
...
