How to write a counter in Java 8?

Writing a counter in Java can be as simple as 2 lines. In addition to its simplicity, we can also utilize the parallel computation to increase the counter's performance.

import java.util.stream.Collectors;

import java.util.stream.Stream;

import java.util.Map;

 

public class Java8Counter {
public static void main(String[] args) {
String[] arr = { "program", "creek", "program", "creek", "java", "web",
"program" };
Stream<String> stream = Stream.of(arr).parallel();
Map<String, Long> counter = stream.collect(Collectors.groupingBy(
String::toString, Collectors.counting()));
System.out.println(counter.get("creek"));
}

}

When you get the map, you may also want to sort the map by value. Check out this post to see how.

参考： http://www.programcreek.com/2014/01/how-to-write-a-counter-in-java-8/