Java Stream count()

In this guide, you will learn about the Stream count() method in Java programming and how to use it with an example.

1. Stream count() Method Overview

Definition:

The Stream.count() method is a terminal operation that returns the count of elements in the stream. This method is particularly useful when you need to determine the size of data after applying intermediate operations like filter, map, etc.

Syntax:

long count()

Parameters:

- The method does not accept any parameters.

Key Points:

- It returns a long value that represents the number of elements in the stream.

- Being a terminal operation, it closes the stream after its execution.

- The count operation is safe to use with parallel streams; the combined count from all threads will be returned.

- It can be computationally intensive for infinite streams, and hence, it's not recommended to use count() on them.

2. Stream count() Method Example

import java.util.stream.Stream;

public class StreamCountExample {
    public static void main(String[] args) {
        Stream<String> fruitsStream = Stream.of("Apple", "Banana", "Cherry", "Date", "Elderberry");

        // Using count to determine the number of elements in the stream
        long count = fruitsStream.count();

        System.out.println("Number of fruits: " + count);
    }
}

Output:

Number of fruits: 5

Explanation:

In the given example, we have a stream of fruit names. Using the count() method, we determine the number of fruits present in the stream, which in this case, returns a count of 5. The result showcases the utility of the count() method in determining the size of the dataset within a stream.