We can submit two types of tasks to <code>forkJoinPool</code>. one is <code>RecursiveAction</code> and other is <code>RecursiveTask</code>. What is the difference between both of them?

From the first lines of their respective Javadocs: <blockquote> <ul> <li>[<code>RecursiveTask</code> is] A recursive result-bearing ForkJoinTask.</li> <li>[<code>RecursiveAction</code> is] A recursive resultless ForkJoinTask.</li> </ul> </blockquote> Although technically, <code>RecursiveAction</code> does return a value, it's just always <code>null</code>, because it's a <code>ForkJoinTask<Void></code>, and that's the only possible value of <code>Void</code>.

They are alike except <code>RecursiveTask</code> returns a result while <code>RecursiveAction</code> has no return value.

Difference between recursive task and recursive action in ForkJoinPool

2 Answers

From the first lines of their respective Javadocs:

[RecursiveTask is] A recursive result-bearing ForkJoinTask.

[RecursiveAction is] A recursive resultless ForkJoinTask.

Although technically, RecursiveAction does return a value, it's just always null, because it's a ForkJoinTask<Void>, and that's the only possible value of Void.