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Comment by ptx

5 hours ago

What's wrong with what .NET did with threads? Having async tasks sharing the GUI thread seems like a nice feature. Will we be able to use virtual threads and structured concurrency with Swing, e.g. to wait for a background task in an event listener?

3 comments

ptx

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revetkn  5 hours ago

Regarding "What's wrong with what .NET did with threads?", see https://cr.openjdk.org/~rpressler/loom/Loom-Proposal.html (relevant part below):

  An alternative solution to that of fibers to concurrency's simplicity vs. performance issue is known as async/await, and has been adopted by C# and Node.js, and will likely be adopted by standard JavaScript. Continuations and fibers dominate async/await in the sense that async/await is easily implemented with continuations (in fact, it can be implemented with a weak form of delimited continuations known as stackless continuations, that don't capture an entire call-stack but only the local context of a single subroutine), but not vice-versa.

  While implementing async/await is easier than full-blown continuations and fibers, that solution falls far too short of addressing the problem. While async/await makes code simpler and gives it the appearance of normal, sequential code, like asynchronous code it still requires significant changes to existing code, explicit support in libraries, and does not interoperate well with synchronous code. In other words, it does not solve what's known as the "colored function" problem.

Regarding Swing, virtual threads are "just" threads so no reason they (and structured concurrency) can't be used.

  • ptx  1 hour ago

    So does Java provide an API for continuations or just the virtual threads hidden behind the threading API? You can't use threads to wait for something on the UI thread (which is why e.g. SwingWorker exists), but you can with await.

  • Athari  2 hours ago

    The colorless functions approach has well-known disadvantages though, including providing less control and making interop a pain. It isn't like one approach is the correct one and another is a mistake.