Run a external application in java but don't wait for it to finish

Question

I'm writing an app in java allowing me to run other applications. To do that, I've used an Process class object, but when I do, the app awaits the process to end before exiting itself. Is there a way to run external application in Java, but don't wait for it to finish?

public static void main(String[] args)
{
FastAppManager appManager = new FastAppManager();
appManager.startFastApp("notepad");
}

public void startFastApp(String name) throws IOException
{
    Process process = new ProcessBuilder(name).start(); 
}

score 3 · Answer 1 · answered Mar 08 '12 at 20:42

3

ProcessBuilder.start() does not wait for process to finish. You need to call Process.waitFor() to get that behaviour.

I did a small test with this program

public static void main(String[] args) throws IOException, InterruptedException {
    new ProcessBuilder("notepad").start();
}

When run in netbeans it appear to be still running. When running from command line with java -jar it returns immediately.

So your program is probably not waiting to exit, but your IDE makes it seem so.

answered Mar 08 '12 at 20:42

Esben Skov Pedersen

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How about when ProcessBuilder runs inside a loop. Does it wait for completion to go to the next loop? – sijo0703 Feb 26 '16 at 01:37
1

If you use waitFor() it will. – Esben Skov Pedersen Feb 26 '16 at 06:29

ebaxt · Answer 2 · 2012-03-08T20:46:30.160

You can run it in another thread.

  public static void main(String[] args) {
        FastAppManager appManager = new FastAppManager();
        appManager.startFastApp("notepad");
    }

    public void startFastApp(final String name) throws IOException {
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        executorService.submit(new Runnable() {
            @Override
            public void run() {
                try {
                    Process process = new ProcessBuilder(name).start();
                } catch (IOException e) {
                    e.printStackTrace();  
                }

            }
        });

    }

You might want to start a daemon thread depending on your needs:

ExecutorService executorService = Executors.newSingleThreadExecutor(new ThreadFactory() {
        @Override
        public Thread newThread(Runnable runnable) {
            Thread thread = new Thread();
            thread.setDaemon(true);
            return thread;
        }
    });

I think he wanted for his lancher to terminate after launching the program. — Tomáš Zato, Jan 10 '16 at 06:48

Run a external application in java but don't wait for it to finish

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