1package eu.siacs.conversations.utils;
 2
 3import java.util.ArrayDeque;
 4import java.util.Queue;
 5import java.util.concurrent.Executor;
 6import java.util.concurrent.Executors;
 7
 8public class SerialSingleThreadExecutor implements Executor {
 9
10	final Executor executor = Executors.newSingleThreadExecutor();
11	final Queue<Runnable> tasks = new ArrayDeque();
12	Runnable active;
13
14	public synchronized void execute(final Runnable r) {
15		tasks.offer(new Runnable() {
16			public void run() {
17				try {
18					r.run();
19				} finally {
20					scheduleNext();
21				}
22			}
23		});
24		if (active == null) {
25			scheduleNext();
26		}
27	}
28
29	protected synchronized void scheduleNext() {
30		if ((active =  tasks.poll()) != null) {
31			executor.execute(active);
32		}
33	}
34}