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Collectors collectingAndThen() method in Java 8
The collectingAndThen() method in Java Collectors class acclimates a Collector to perform an additional finishing transformation. It returns collector which performs the action of the downstream collector, followed by an additional ending step.
The syntax is as follows.
static <T,A,R,RR> Collector<T,A,RR> collectingAndThen(Collector<T,A,R> downstream, Function<R,RR> finisher)
Here, the parameter,
T − Type of the input elements
A − Intermediate accumulation type of the downstream collector
R − The result type of the downstream collector
RR − The result type of the resulting collector
downstream − Collector
finisher − A function to be applied to the final result of the downstream collector
To work with Collectors class in Java, import the following package.
import java.util.stream.Collectors;
The following is an example to implement collectingAndThen() method in Java.
Example
import java.util.List;
import java.util.Collections;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class Demo {
public static void main(String[] args) {
List<String> list
= Stream.of("Demo1", "Demo2").collect(Collectors.collectingAndThen(
Collectors.toList(),
Collections::<String> unmodifiableList));
System.out.println(list);
}
}Output
[Demo1, Demo2]
Updated on: 30-Jul-2019
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