CancellationException when using ExecutorService

Question

I want to wait two tasks to finish then return the result of them but sometimes I get this error. Why? Where did CancellationException come from?

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Answer 1

You ask your executor service to execute your callables with a timeout of 5 seconds. According to the javadoc:

tasks that have not completed [by the end of the timeout] are cancelled

My guess is that future.get() throws a CancellationException because the timeout has been reached and the executor calls future.cancel().

You could either:

• increase the timeout
• catch an InterruptedException in your callable to handle the cancellation gracefully