I have this C# code:
Action action = MyFunction;
action.BeginInvoke(action.EndInvoke, action);
which, from what I can tell, just runs MyFunction asynchronously. Can you do the same thing in Java?
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3 Answers
This is how you could run an action in its own thread in Java:
new Thread(new Runnable() {
@Override
public void run() {
aFunctionThatRunsAsynchronously();
}
}).start();
There are other higher-level frameworks available that give you more control on how things are run such as Executors, which can for example be used to schedule events.
3 Comments
weston
BeginInvoke will use the thread pool, is there such a concept in Java? - Sorry, I should have taken a second to follow your "Executors" link! Thanks
adam0101
When I try this I get the error "The method run() of type new Runnable(){} must override a superclass method".
assylias
@adam0101 Not sure why: it works on my machine. What version of Java JDK are you using? If you use Java 5 or earlier, you might need to remove the
@Override annotation (stackoverflow.com/questions/2135975/…).Natively, the ExecutorService provides the closest I can think of. Here's how you can use the ExecutorService to run a method async and then get the return value later:
ExecutorService executor = Executors.newFixedThreadPool(NTHREDS);
Future<String> future = executor.submit(new Callable<String>() {
return getSomeLongRunningSomethingHere();
});
//... do other stuff here
String rtnValue = future.get(); //get blocks until the original finishes running
System.out.println(rtnValue);
Comments
This is somewhat related to Asynchronous Event Dispatch in Java. Basically, you can structure the method you want to run as a class implementing Callable or Runnable. Java doesn't have the ability to refer to a "method group" as a variable or parameter, like C# does, so even event handlers in Java are classes implementing an interface defining the listener.
Try something like this:
Executor scheduler = Executors.newSingleThreadExecutor();
//You'd have to change MyFunction to be a class implementing Callable or Runnable
scheduler.submit(MyFunction);
More reading from the Oracle Java docs:
http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/Executors.html
http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/ScheduledExecutorService.html
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