Discover the Difference Between parallelStream() and stream().parallel() in Java

Difference Between parallelStream() and stream().parallel() in Java

In Java 8, the introduction of the Streams API opened up a whole new world of potential for developers. Streams provide an easy and efficient way to process large collections of data without having to write complex loops or manually talk to the database. The two main methods of creating Parallel Streams in Java are parallelStream() and stream().parallel(). While they both offer similar functionalities, there are some subtle differences that can be important in certain situations.

parallelStream()

parallelStream() is a terminal operation on a collection. It returns a Parallel Stream object which can be used for parallel processing of elements within the collection. The advantage of using parallelStream() is that it can potentially increase performance by allowing multiple threads to access the same data at the same time. This is useful for large datasets where splitting the work amongst many threads can be beneficial.

stream().parallel()

The other option for creating Parallel Streams in Java is stream().parallel(). As with parallelStream(), this method creates a Parallel Stream object which can be used to process elements within the collection. However, the difference between these two methods is how they are used. stream().parallel() is an intermediate operation that needs to be followed by a terminal operation. That is, you can use stream().parallel() on a Stream that has already been created and then follow it up with a terminal operation such as count() or collect(). This provides the flexibility to process the data in different ways, depending on the needs of the application.

Conclusion

Both parallelStream() and stream().parallel() provide efficient ways to process data in parallel. The key difference between these two methods is that parallelStream() is a terminal operation, whereas stream().parallel() is an intermediate operation that needs to be followed by a terminal operation. Therefore, it is important to understand when and how to use each of these methods to maximize the performance of your application.