ExecutorService that executes tasks sequentially but takes threads from a pool

Question

I am trying to build an implementation of the ExecutorService, let\'s call it SequentialPooledExecutor, with the following properties.

Answer 1

Recently I encountered the same problem. There is no built-in class for this, but a queue is close enough. My simple implementation looks like this (maybe it's helpful for others looking for examples on the same issue)

public class SerializedAsyncRunnerSimple implements Runnable {
private final ExecutorService pool;
protected final LinkedBlockingQueue queue = new LinkedBlockingQueue<>(); //thread safe queue
protected final AtomicBoolean active = new AtomicBoolean(false);


public SerializedAsyncRunnerSimple(ExecutorService threadPool) {this.pool = threadPool;}


public void addWork(Runnable r){        
    queue.add(r);
    startExecutionIfInactive();
}

private void startExecutionIfInactive() {
    if(active.compareAndSet(false, true)) {
        pool.execute(this);
    }
}

@Override
public synchronized void run() {
    while(!queue.isEmpty()){
        queue.poll().run();
    }
    active.set(false); //all future adds will not be executed on this thread anymore
    if(!queue.isEmpty()) { //if some items were added to the queue after the last queue.poll
        startExecutionIfInactive();// trigger an execution on next thread
    }
}