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Tag: thread

Exception handling in ScheduledExecutorService

Java’s ScheduledExecutorService allows you to schedule Runnable tasks without having to worry too much about creating Threads. At its simplest, you can schedule a task like this:

Runnable task = () -> System.out.println("Hello world!");
executor.schedule(task, 10, TimeUnit.SECONDS);

The output is:

Hello world!

That is we schedule the task, then print “Done!”. 10 seconds later the scheduled task executes and prints “Hello world!”.

But what happens if the Runnable throws an Exception?

Testing for SimpleDateFormat thread safety

It’s a little alarming how many good developers are unaware that many standard Java classes – including subclasses of Format – are not thread safe. Many are also not sure about how their applications perform in a multi-threaded environment or how their web application container (Tomcat) will run their app in multiple threads. This can cause nasty intermittent bugs that can be incredibly hard to find and fix. It’s important to be aware of threading issues at development time but it’s also important to be able to test for them.