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Reactive Programming with RxJava

Streams

Learn about data streams in Java and RxJava and why we prefer RxJava streams.

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Java’s streams

If we think about it, a stream is not a new concept. A Collection in Java can be modeled as a stream where each element in the Collection is an item emitted in the stream.

On Android, click events can be a stream, location updates can be a stream, push notifications can be a stream, and so on.

Imperative vs. declarative approach

Traditionally, processing data streams in Java is done imperatively. For example, given a list of User objects, say we want to return only those that have a blog. That function might look something like this:

Java
/**
 * Returns all users with a blog.
 * @param users the users
 * @return users that have a blog
 */
public static List<User> getUsersWithABlog(List<User> users) {
    List<User> filteredUsers = new ArrayList<>();
    for (User user : users) {
        if (user.hasBlog()) {
            filteredUsers.add(user);
        }
    }
    return filteredUsers;
}

The above code might look very familiar: a loop that iterates through each item in the provided collection, an if-statement to check if a condition is true, and for those that pass, the necessary action is performed, meaning that the item is added ...