How to interrupt CompletableFuture::join?

user_1813988 0
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I've found that CompletableFuture::join seems uninterruptible when not completed:

// CompletableFuture::join implementation from JDK 8 sources
public T join() { 
    Object r;
    return reportJoin((r = result) == null ? waitingGet(false) : r);
}

In above implementation, waitingGet(false) will ignore the interrupt flag of the working Thread and continue waiting. I'm wondering how can I interrupt a Thread in which I call CompletableFuture::join.

completable-future java-8 interrupt multithreading java
3 Answers

I clearly known in the end you are not actually looking for the interruptible, but as a way around it can be interrupted by exceptions as follows (though it's join()):

private static void testCompleteExceptionally() {
    String name = "Hearen";
    CompletableFuture<String> completableFuture
            = CompletableFuture.supplyAsync(() -> {
        delay(500L);
        if (name == null) {
            throw new RuntimeException("Computation error!");
        }
        return "Hello, " + name;
    });

    if (name != null) {
        completableFuture.completeExceptionally(new RuntimeException("Calculation failed!"));
    }
    out.println(completableFuture.handle((s, t) ->  s != null ? s : "Hello, Stranger!" + t.toString()).join());
}
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