Parallel Streams - nus-cs2030/2122-s1 GitHub Wiki

When To Use parallel()

• When the output of the stream does not depend on the order of the elements

• When better performance is needed after considering the large overheading of Parallelizing

  (FYI: NxQ rule of thumb to expect better performance with parallel: N(number of element) x Q(work per element) > 10k)

To Ensure Proper Execution of Parallel Stream

• Does not interfere with stream data like adding/deleting elements from the stream directly (same goes for sequential stream)
• Preferably Stateless (cf. sorted and limit which are stateful) with no side effects
  • This is due to elements being completely processed at different times as shown below

jshell> Stream.of(10, 100, 1000).
   ...>     parallel().
   ...>     forEach(x -> System.out.println(x))
100
1000
10

- Use sequential() to switch off parallel operation

Also here's also the link the class mentioned to better learn streams