How to reduce a limited stream (e.g. an ArrayList) from right in Java?

I would like to convert a list to a self-implemented linked list using reduce. I managed to do that in a reverse order: import java.util.Arrays; import java.util.List; public class Reverse { …

Java Stream why does reduce requires two parameters of the functional Interface?

In other words, why does reduce require BinaryOperator, or BiFunction interface? Why doesn’t it use UnaryOperator, or Function interface instead? What is the point of having two parameters as the …

Group by multiple fields and filter by common value of a field

@Data public class Employee{ private int empid; private String empPFcode; private String collegeName; } Employee emp1=new Employee (1334090,”220″,”AB”); Employee …

parallel() not work with the 3-arg iterate()

Here is my code: int count=20; Stream.iterate(4,i->ii+1).parallel().forEach(i -> { try { Thread.sleep(new Random().nextInt(2000)); } catch (InterruptedException …

Map List to Map with additional transformation

I need to convert a list of objects to a map of sets of one of the objects’ property and I’d like to use Java streams for that. For example there is a List and I’d like to convert it to a …

Convert nested map of streams.groupingBy() into list of POJOs

I want to convert a nested map structure created by java streams + groupingBy into a list of POJOs, where each POJO represents one of the groups and also holds all the matching objects of that group. …

Using Streams and StreamSupplier: forEach closes StreamSupplier instead of instance of stream

I am making a obj file loader for an engine that I’m writing and I am trying to use Streams to load vertex index, uvcoord, and normals from this file. The way I intended to do this was to create a new …

Are stream elements sorted? [closed]

Is there a way to find if the elements taken from a Stream in encounter order, are all sorted in ascending order? (The stream source could be absolutely anything, from Arrays.stream() to Files.lines(),…

How to Iterate list of list of Java Objects using Java 8

How to iterate and get through list of list of objects using Java 8 Also need to get the count of distinct customerIds final List issues = customerIssues.collectList().block(); …

‘OptionalDouble.getAsDouble()’ without ‘isPresent()’ check

I’ve seen a bunch of solutions for this question but no matter what I try, IDEA still reports an error. Consider the following block: double testDouble= customClass.stream() .mapToDouble(…