29 August 2019

Java 8 parallel streams pitfall

All parallel streams use a common fork-join thread pool, and if you submit a long-running task, you effectively block all threads in the pool. Consequently, you block all other tasks that are using parallel streams.

The default processing that occurs in such a Stream uses the ForkJoinPool.commonPool(), a Thread Pool shared by the entire application.

This way we essentially force the parallel stream to have a ForkJoin as a parent thread, instead of a regular thread, so ForkJoinPool.commonPool is not used. Hooray!

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