Questions tagged [groupingby]
77 questions
2
votes
2 answers
How to aggregate grouped entities after stream groupingBy
I have a simple class Person:
class Person {
String firstName;
String lastName;
//getter, setter, constructor, toString
}
And an input list of Persons like:
List myList = List.of(
new Person("Helena", "Graves"),
…
wannaBeDev
- 516
- 3
- 14
2
votes
2 answers
can return java stream groupingby to this's array variable?
Q.1)
hi, java stream's groupingby can make oneself's array varible?
this is entity
public class Test {
private int id;
private int itemId;
private int[] itemIds;
private boolean filter;
}
this is test List sample
{
test(id=1,…
gd k GD
- 23
- 4
2
votes
3 answers
Java Collectors Grouping By
I have an input of integers and I would like to sort all even numbers before all odd ones in ascending order and preserve the odds order. I am pretty sure I can achieve that with collectors and/or downstream collectors, but I am not sure how to do…
unknownerror
- 39
- 8
2
votes
2 answers
Java Stream Grouping by multiple fields individually in declarative way in single loop
I googled for it but I mostly found cases for grouping by aggregated fields or on to alter response of stream but not the scenario below:
I have a class User with fields category and marketingChannel.
I have to write a method in the declarative…
FarazAhmed
- 43
- 6
2
votes
2 answers
Stream collectingAndThen get latest record to sum a value
Currently, I'm facing with below dataset. My aim is to get the latest sum of Column4 group by the first two-column.
// Column5 = version
new Foo(1, "bbb", "cccc", 111, 0)
new Foo(1, "bbb", "cccc", 234, 1) // latest
new Foo(1, "bbb", "dddd", 111,…
Vincent Tang
- 137
- 8
2
votes
1 answer
Java 8 groupingBy to obtain LinkedHashMap and mapping the values of the map to a different object
I have this method which returns a Map:
public Map> getAccountsByGroupNameMap(final List accountManagementList) {
return new…
elena A
- 35
- 1
- 6
2
votes
2 answers
GroupingBy with List as a result
We have the following:
public List mapToBalancesWithSumAmounts(List entries) {
return entries
.stream()
.collect(
groupingBy(
MonthlyBalancedBooking::getValidFor,
…
Christian Wiedehöft
- 41
- 4
2
votes
2 answers
split a list into sublists by grouping **only** repeated elements that are adjacent to each other
Is there a simple way to split a list into sublists by grouping only repeated elements that are adjacent to each other?
Simple example with the folowing list of strings:
Input: [RED,RED,BLUE,BLUE,BLUE,GREEN,BLUE,BLUE,RED,RED]
Output: …
wannaBeDev
- 516
- 3
- 14
1
vote
1 answer
Java8-stream complex groupingBy
I want to do groupingBy and create a map that return me >
my model is as below
public class Partition {
private String tableName;
private int vendorKey;
private int retailerKey;
private int periodKey;
private…
Shalaj
- 579
- 8
- 19
1
vote
1 answer
Can I add element while using Java stream groupingby
For loop code is this.
Param : ArrayList userList
Map map = new HashMap();
for (User user : userList) {
String[] arr = user.getStringSeq().split(DELIMITER);
String key = String.join(DELIMITER, arr[MENU_IDX],…
Ji Chang-jin
- 11
- 1
1
vote
1 answer
Java-Stream - Group by Array 4 elements and add up threir last elements using Java 8
I have a list of string arrays List which looks like this:
List dataLines = List.of(
new String[]{"2002", "BRBTSS", "BRSTNCNTF212", "BRL", "12670012.4055", "84M", "-101.87", "0"},
new String[]{"2002", "BRBTSS",…
prachi Kadam
- 19
- 3
1
vote
2 answers
Java-Stream - How to apply sorting while using Collector groupingBy
I'm using Collectors.groupingBy to group may objects into list. Examples are as follows:
public class Test {
public static void main(String[] args) {
Student student1 = new Student(98,"man","CHEN",20);
Student student2 = new…
jane
- 61
- 5
1
vote
2 answers
Java-Stream - How Collecor groupingBy() to split a Map into multiple Submaps
I have the following Student object:
public class Student {
private String gradeAndClass;
private String gender;
private String name;
// getters, constructor, etc.
}
In the original code, properties gradeAndClass and gender are…
guiqin
- 53
- 4
1
vote
2 answers
Creating Map of Maps using a custom Object as a reduction type in Java 8
I have a List
class MyObject {
String loanType;
String loanCurrency;
BigDecimal amountPaid;
BigDecimal amountRemaining;
}
And I need to convert this list into a map Map.
I've created a…
jasmeet
- 37
- 4
1
vote
1 answer
Java Stream - groupingBy() and counting() when a curtain Condition is met
Given the following class Test
class Test {
String testName;
String studName;
String status;
}
and a list of tests
List tests = List.of(
new Test("English", "John", "passed"),
new Test("English", "Dave",…
bbKing
- 179
- 1
- 8