I’ve seen lambdas performance and streams much better than using repetition loops, so I try to use as much as possible.
My question is when should I use Streams or ParallelStreams? How does this parallelism of streams occur?
The Streams API available from Java 8 now has several benefits, let’s first define the serial algorithm vs. the parallel algorithm.
I recommend reading this question, my answer seeks to explore these two paradigms of computing: #
Now that we understand parallelism, let’s go to Streams …
According to Oracle
You can run
Stream in series or in parallel ( Serial or Parallel ). When
Stream is executed in parallel, java partitions or splits
Stream s into various substreams. Aggregation operations iterate and process these substreams in parallel, and then combine the results.
In other words
Parallel stream is intended to allow processing to be split between the processors on your machine, for example, if you need to sort a large
Collection , this can be done serially , and consequently by a single
Thread , or in parallel, with two or more
What it means to say that
Collection is broken into two subcollections, and ordered in parallel, which in theory reduces the time spent in half.
The point of great importance is: this is not always true. Even why this may depend on how many processors you have.
Parallel Streams can make your program faster, or not, and even slower.
Depends on which operations in
Streams you use, not all are actually parallelized