Question

Here’s what I have:

public class Queue implements Runnable {
    ArrayList<Point> queue;

    public Queue(){
        this.queue=new ArrayList<Point>();
    }

    synchronized public void cuePoint(Point p){
        this.queue.add(p);
    }
    synchronized public void doFirstPoint(){
        if(queue.size()!=0){
            //some operation that takes a real long time
            queue.remove(0);
        }
    }

    synchronized public void clearQueue(){
        this.queue.clear();
    }

    public void run() {
        while(true){
            doFirstPoint();
        }
    }
}

However, the problem with this code is that if the queue thread is working on a point in the queue (which, as noted, takes a real long time) the cuing thread is kept waiting. Is there a simple, intuitive way to fix this?

Answer 1

There’s a class in java called ArrayBlockingQueue which does what you are trying to do and it is thread safe.

public BlockingQueue<Point> pointQueue = new ArrayBlockingQueue<Point>();