Safe subList operator for RxJava

subList.java

public class subList<T> implements Observable.Operator<List<T>, List<T>> {

    private int start;
    private int length;

    public subList(int start, int length) {
        this.start = start;
        this.length = length;
    }

    public subList(int length) {
        this(0, length);
    }

    @Override
    public Subscriber<? super List<T>> call(Subscriber<? super List<T>> subscriber) {
        return new Subscriber<List<T>>() {
            @Override
            public void onCompleted() {
                if (!subscriber.isUnsubscribed()) {
                    subscriber.onCompleted();
                }
            }

            @Override
            public void onError(Throwable e) {
                if (!subscriber.isUnsubscribed()) {
                    subscriber.onError(e);
                }
            }

            @Override
            public void onNext(List<T> ts) {
                if (!subscriber.isUnsubscribed()) {

                    int maxValue = Math.min(ts.size(), start + length);
                    subscriber.onNext(ts.subList(start, maxValue));
                }
            }
        };
    }
}