Whats the maximum number of swing worker threads that can be run

A SwingWorker is not a thread itself but a task that will be executed in a thread. Usually, you would use an ExecutorService to execute instances of SwingWorker; this interface also allows to set the number of threads:

 int n = 20; // Maximum number of threads ExecutorService threadPool = Executors.newFixedThreadPool(n); SwingWorker w; //don't forget to initialize threadPool.submit(w);

Now, if you submit more than n SwingWorker instances, they'll have to queue up and wait until a thread from the pool gets available.

final int corePoolSize = 100;final int maximumPoolSize = 100;final long keepAliveTime = 100000;final TimeUnit unit = TimeUnit.SECONDS;final BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(maximumPoolSize);sun.awt.AppContext.getAppContext().put(SwingWorker.class,                 new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue));

The above code sample will allow you to have more than the default number of SwingWorkers executing. Of course it is accessing some backdoor sun.awt.AppContext class, but it is a quick workaround for those interested, and not able/willing to provide their own ExecutorService.