What is Collectors.maxBy() in Java?
The Collectors class
Collectors is a utility class that provides various implementations of reduction operations such as grouping, collecting, and summarizing elements.
The different functionalities in the Collectors class are used as final operations on streams.
The maxBy() method
maxBy() is a static method of the Collectors class that is used to find the maximum element of the input elements using the passed comparator.
The maxBy method is defined in the Collectors class. The Collectors class is defined in the java.util.stream package.
To import the Collectors class, use the following import statement:
import java.util.stream.Collectors;
Syntax
public static <T> Collector<T, ?, Optional<T>> maxBy(Comparator<? super T> comparator)
Parameters
Comparator<? super T> comparator: Used for comparison.
Return value
This method returns a Collector class that uses the given comparator to compute the maximum element.
Code
import java.util.Arrays;import java.util.Comparator;import java.util.List;import java.util.Optional;import java.util.stream.Collectors;import java.util.stream.Stream;public class Main {public static void main(String[] args){List<String> stringList = Arrays.asList("educative", "io", "edpresso");System.out.println("Stream before modification - " + stringList);Stream<String> stringStream = stringList.stream();Optional<String> maxElement = stringStream.collect(Collectors.maxBy(Comparator.naturalOrder()));System.out.println("Maximum element of the stream - " + (maxElement.orElse("null")));}}
Explanation
- Lines 1–4: We import the relevant packages.
- Line 10: We define a list of strings called
stringList. - Line 12: We print
stringList. - Line 14: We create a stream out of
stringList. - Line 16: We use the
maxBymethod to get the maximum element. We pass the naturalOrder comparator as the argument to themaxBymethod. - Line 18: We print the maximum element.