JCTools.java

public class JCTools {
    
    private volatile Thread sleeping;
  
    <T> void add(Queue<? super T> q, T e) {
        while (!q.offer(e)) {
            // TODO: FIXME - cannot happen in production (even if is what some does!)
            LockSupport.parkNanos(1L);
        }
        LockSupport.unpark(sleeping);
    }

    <T> T take(Queue<? extends T> q) {
        for (; ; ) {
            T e = q.poll();
            if (e != null) {
                return e;
            }
            sleeping = Thread.currentThread();
            try {
                e = q.poll();
                if (e != null) {
                    return e;
                }
                LockSupport.park();
                // can spuriously wakeup!
            } finally {
                sleeping = null;
            }
        }
    }

}