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Java streams counting() method with examples

  • Last Updated : 06 Dec, 2018
Geek Week

In Java 8, there is predefined counting() method returned by Collectors class counting() method to count the number of elements in a Stream.

Syntax :
public static Collector counting() Where, output is a Collector, acting on a Stream of elements of type T, with its finisher returning the ‘collected’ value of type Long. It is a terminal operation which returns the total count of elements in the stream which reach the collect() method after undergoing various pipelined stream operations such as filtering.

Example 1 : To count the elements in stream of Integers.




// Java code to count number of elements 
// in stream
import java.util.stream.Stream;
import java.util.stream.Collectors;
class counting {
    public static void main(String[] args)
    {
        // creating stream of integers
        Stream<Integer> i = Stream.of(1, 2, 3, 4, 5, 6);
  
        // counting number of integer in stream
        long count_int = i.collect(Collectors.counting());
  
        System.out.println(count_int);
    }
}
Output:
6

Example 2 : To count the elements in stream of String.




// JAVA code to count number of elements in stream
import java.util.stream.Stream;
import java.util.stream.Collectors;
  
class counting {
    public static void main(String[] args)
    {
        // creating stream of strings
        Stream<String> s = Stream.of("Akash","Harsh",
                        "Shubham","Nishant","Pratik");
  
        // counting number of strings in stream
        long count_string =  s.collect(Collectors.counting());
  
        System.out.println(count_string);
    }
}
Output:
5

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