src/main/java/io/reactivex/disposables/CompositeDisposable.java
public int size() {
        if (disposed) {
            return 0;
        }
        synchronized (this) {
            if (disposed) {
                return 0;
            }
            OpenHashSet<Disposable> set = resources;
            return set != null ? set.size() : 0;
        }
    }
public int size() {
        if (disposed) {
            return 0;
        }
        synchronized (this) {
            if (disposed) {
                return 0;
            }
            OpenHashSet<Disposable> set = resources;
            return set != null ? set.size() : 0;
        }
    }
Returns the number of currently held Disposables.
@return the number of currently held Disposables