driver-core/src/main/com/mongodb/internal/connection/ConcurrentPool.java
@Override
    public void close() {
        closed = true;
        Iterator<T> iter = available.iterator();
        while (iter.hasNext()) {
            T t = iter.next();
            close(t);
            iter.remove();
        }
    }
@Override
    public void close() {
        closed = true;
        Iterator<T> iter = available.iterator();
        while (iter.hasNext()) {
            T t = iter.next();
            close(t);
            iter.remove();
        }
    }
Clears the pool of all objects.