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Managing The Reactive World Jake Wharton

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Managing The Reactive World (with RxJava) Jake Wharton

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Why Reactive? Unless you can model your entire system synchronously...

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Why Reactive? Unless you can model your entire system synchronously, a single asynchronous source breaks imperative programming.

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Why Reactive? interface UserManager { User getUser();
 }A

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Why Reactive? interface UserManager { User getUser(); void setName(String name); void setAge(int age);
 }A

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Why Reactive? interface UserManager { User getUser(); void setName(String name); void setAge(int age);
 }A UserManager um = new UserManager();

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Why Reactive? interface UserManager { User getUser(); void setName(String name); void setAge(int age);
 }A UserManager um = new UserManager(); System.out.println(um.getUser());

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Why Reactive? interface UserManager { User getUser(); void setName(String name); void setAge(int age);
 }A UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe");

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Why Reactive? interface UserManager { User getUser(); void setName(String name); void setAge(int age);
 }A UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe"); System.out.println(um.getUser());

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Why Reactive? interface UserManager { User getUser(); void setName(String name); // <-- now async void setAge(int age); // <-- now async
 }A

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Why Reactive? interface UserManager { User getUser(); void setName(String name); void setAge(int age);
 }A UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe"); System.out.println(um.getUser());

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Why Reactive? interface UserManager { User getUser(); void setName(String name, Runnable callback); void setAge(int age, Runnable callback);
 }A

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Why Reactive? interface UserManager { User getUser(); void setName(String name, Runnable callback);A void setAge(int age, Runnable callback);B
 }A UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe", new Runnable() { @Override public void run() { System.out.println(um.getUser()); }X });

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Why Reactive? interface UserManager { User getUser(); void setName(String name, Listener listener);A void setAge(int age, Listener listener);B interface Listener { void success(User user); void failure(IOException e); }G
 }A

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Why Reactive? UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe");

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Why Reactive? UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { System.out.println(um.getUser()); }A @Override public void failure(IOException e) { // TODO show the error... }B });

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Why Reactive? UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { System.out.println(um.getUser()); }A @Override public void failure(IOException e) { // TODO show the error... }B }); um.setAge(40, new UserManager.Listener() { @Override public void success() { System.out.println(um.getUser()); }C 2@Override public void failure(IOException e) {2 2// TODO show the error...2 }D });2

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Why Reactive? UserManager um = new UserManager(); System.out.println(um.getUser()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { System.out.println(um.getUser()); um.setAge(40, new UserManager.Listener() { @Override public void success() { System.out.println(um.getUser()); }C 2@Override public void failure(IOException e) {2 2// TODO show the error...2 }D });2 }A @Override public void failure(IOException e) { // TODO show the error... }B });

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Why Reactive? public final class UserActivity extends Activity { private final UserManager um = new UserManager(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.user); TextView tv = (TextView) findViewById(R.id.user_name); tv.setText(um.getUser().toString()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { tv.setText(um.getUser().toString()); }A @Override public void failure(IOException e) { // TODO show the error... }B }); }Y }Z System.out.println(um.getUser()); System.out.println(um.getUser()); um.setAge(40, new UserManager.Listener() { @Override public void success() { System.out.println(um.getUser()); }C 2@Override public void failure(IOException e) {2 2// TODO show the error...2 }D });2

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Why Reactive? public final class UserActivity extends Activity { private final UserManager um = new UserManager(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.user); TextView tv = (TextView) findViewById(R.id.user_name); tv.setText(um.getUser().toString()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { tv.setText(um.getUser().toString()); }A @Override public void failure(IOException e) { // TODO show the error... }B }); }Y }Z

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Why Reactive? public final class UserActivity extends Activity { private final UserManager um = new UserManager(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.user); TextView tv = (TextView) findViewById(R.id.user_name); tv.setText(um.getUser().toString()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { if (!isDestroyed()) { tv.setText(um.getUser().toString()); } }A @Override public void failure(IOException e) { // TODO show the error... }B }); }Y }Z

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Why Reactive? public final class UserActivity extends Activity { private final UserManager um = new UserManager(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.user); TextView tv = (TextView) findViewById(R.id.user_name); tv.setText(um.getUser().toString()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { if (!isDestroyed()) { tv.setText(um.getUser().toString()); } }A @Override public void failure(IOException e) { // TODO show the error... }B }); }Y }Z

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Why Reactive? public final class UserActivity extends Activity { private final UserManager um = new UserManager(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.user); TextView tv = (TextView) findViewById(R.id.user_name); tv.setText(um.getUser().toString()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { if (!isDestroyed()) { tv.setText(um.getUser().toString()); }L }A @Override public void failure(IOException e) { // TODO show the error... }B }); }Y }Z

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Why Reactive? public final class UserActivity extends Activity { private final UserManager um = new UserManager(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.user); TextView tv = (TextView) findViewById(R.id.user_name); tv.setText(um.getUser().toString()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { runOnUiThread(new Runnable() { @Override public void run() { if (!isDestroyed()) { tv.setText(um.getUser().toString()); }L }4 }); }A @Override public void failure(IOException e) { // TODO show the error... }B }); }Y }Z

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Why Reactive? public final class UserActivity extends Activity { private final UserManager um = new UserManager(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.user); TextView tv = (TextView) findViewById(R.id.user_name); tv.setText(um.getUser().toString()); um.setName("Jane Doe", new UserManager.Listener() { @Override public void success() { runOnUiThread(new Runnable() { @Override public void run() { if (!isDestroyed()) { tv.setText(um.getUser().toString()); } }4 }); }A @Override public void failure(IOException e) { // TODO show the error... }B }); }Y }Z

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Why Reactive? GET / 200 OK SELECT * Jane Doe setText onClick

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Why Reactive? GET / 200 OK SELECT * Jane Doe setText onClick

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Why Reactive? GET / 200 OK SELECT * Jane Doe setText onClick

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Why Reactive? GET / 200 OK SELECT * Jane Doe setText onClick

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Why Reactive? GET / 200 OK SELECT * Jane Doe setText onClick

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Why Reactive? GET / 200 OK SELECT * Jane Doe setText onClick SELECT * Jane Doe setText UPDATE user Jane Doe setText

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Why Reactive?

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Why Reactive? Unless you can model your entire system synchronously, a single asynchronous source breaks imperative programming.

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Why Reactive?

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Why Reactive?

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Why Reactive?

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Why Reactive?

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Why Reactive?

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Why Reactive?

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RxJava

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RxJava • A set of classes for representing sources of data.

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RxJava • A set of classes for representing sources of data. • A set of classes for listening to data sources.

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RxJava • A set of classes for representing sources of data. • A set of classes for listening to data sources. • A set of methods for modifying and composing the data.

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RxJava • A set of classes for representing sources of data. • A set of classes for listening to data sources. • A set of methods for modifying and composing the data.

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Sources

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Sources • Usually do work when you start or stop listening.

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Sources • Usually do work when you start or stop listening. • Synchronous or asynchronous.

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Sources • Usually do work when you start or stop listening. • Synchronous or asynchronous. • Single item or many items.

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Sources • Usually do work when you start or stop listening. • Synchronous or asynchronous. • Single item, many items, or empty.

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Sources • Usually do work when you start or stop listening. • Synchronous or asynchronous. • Single item, many items, or empty. • Terminates with an error or succeeds to completion.

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Sources • Usually do work when you start or stop listening. • Synchronous or asynchronous. • Single item, many items, or empty. • Terminates with an error or succeeds to completion. • May never terminate!

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Sources • Usually do work when you start or stop listening. • Synchronous or asynchronous. • Single item, many items, or empty. • Terminates with an error or succeeds to completion. • May never terminate! • Just an implementation of the Observer pattern.

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• Observable • Flowable void void
 Sources

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• Observable • Emits 0 to n items. • Terminates with complete or error. • Flowable • Emits 0 to n items. • Terminates with complete or error. void void
 Sources

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• Observable • Emits 0 to n items. • Terminates with complete or error. • Does not have backpressure. • Flowable • Emits 0 to n items. • Terminates with complete or error. • Has backpressure. void void
 Sources

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Flowable vs. Observable

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Flowable vs. Observable • Backpressure allows you to control how fast a source emits items.

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Flowable vs. Observable • Backpressure allows you to control how fast a source emits items. • RxJava 1.x added backpressure late in the design process.

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Flowable vs. Observable • Backpressure allows you to control how fast a source emits items. • RxJava 1.x added backpressure late in the design process. • All types exposed backpressure but not all sources respected it.

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Flowable vs. Observable • Backpressure allows you to control how fast a source emits items. • RxJava 1.x added backpressure late in the design process. • All types exposed backpressure but not all sources respected it. • Backpressure must be designed for.

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Flowable vs. Observable • Backpressure must be designed for.

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView);

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView);

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView); Observable rows = db.createQuery("SELECT * …");

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView); Observable rows = db.createQuery("SELECT * …");

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView); Observable rows = db.createQuery("SELECT * …");

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView); Observable rows = db.createQuery("SELECT * …");

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView); Observable rows = db.createQuery("SELECT * …"); MissingBackpressureException

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Flowable vs. Observable • Backpressure must be designed for. Observable events = RxView.touches(paintView); Flowable rows = db.createQuery("SELECT * …");

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Flowable vs. Observable Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B

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Flowable vs. Observable Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B

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Flowable vs. Observable Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B

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Flowable vs. Observable Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B

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Flowable vs. Observable Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B

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Flowable vs. Observable Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B interface Disposable {
 void dispose();
 }B

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Flowable vs. Observable Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B interface Disposable {
 void dispose();
 }B interface Subscription {
 void cancel();
 void request(long r);
 }B

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Backpressure No Backpressure 0…n items, complete|error Flowable Observable

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Reactive Streams ...is an initiative to provide a standard for asynchronous stream processing with non-blocking back pressure.

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Reactive Streams interface Publisher {
 void subscribe(Subscriber super T> s);
 }A

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Reactive Streams interface Publisher {
 void subscribe(Subscriber super T> s);
 }A interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B

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Reactive Streams interface Publisher {
 void subscribe(Subscriber super T> s);
 }A interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Subscription {
 void request(long n);
 void cancel();
 }C

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Reactive Streams interface Publisher {
 void subscribe(Subscriber super T> s);
 }A interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Subscription {
 void request(long n);
 void cancel();
 }C interface Processor extends Subscriber, Publisher {
 }D


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Reactive Streams (Backpressure) No Backpressure 0…n items, complete|error Flowable Observable

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interface UserManager { User getUser(); void setName(String name); void setAge(int age);
 }A Sources

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Sources interface UserManager { Observable getUser(); void setName(String name); void setAge(int age);
 }A

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Source Specializations • Encoding subsets of Observable into the type system.

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Single • Either succeeds with an item or errors. • No backpressure support.

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Single • Either succeeds with an item or errors. • No backpressure support. • Think "reactive scalar".

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Completable • Either completes or errors. Has no items! • No backpressure support.

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Completable • Either completes or errors. Has no items! • No backpressure support. • Think "reactive runnable".

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Maybe • Either succeeds with an item, completes with no items, or errors. • No backpressure support.

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Maybe • Either succeeds with an item, completes with no items, or errors. • No backpressure support. • Think "reactive optional".

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Source Specializations • Encoding subsets of Observable into the type system. • Single – Item or error. Think "scalar". • Completable – Complete or error. Think "runnable". • Maybe – Item, complete, or error. Think "optional".

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Reactive Streams (Backpressure) No Backpressure 0…n items, complete|error Flowable Observable item|complete|error Maybe item|error Single complete|error Completable

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Sources interface UserManager { Observable getUser(); void setName(String name); void setAge(int age);
 }A

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Sources interface UserManager { Observable getUser(); Completable setName(String name); Completable setAge(int age);
 }A void void


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Creating Sources Flowable.just("Hello");
 Flowable.just("Hello", "World"); 
 Observable.just("Hello");
 Observable.just("Hello", "World");
 Maybe.just("Hello");
 Single.just("Hello");

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Creating Sources String[] array = { "Hello", "World" };
 List list = Arrays.asList(array);
 Flowable.fromArray(array); Flowable.fromIterable(list); Observable.fromArray(array); Observable.fromIterable(list);

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Creating Sources Observable.fromCallable(new Callable() {
 @Override public String call() {Y
 return getName();
 }X
 });

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Creating Sources Observable.fromCallable(new Callable() {
 @Override public String call() throws Exception {Y
 return getName();Z
 }X
 });

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Creating Sources OkHttpClient client = // … Request request = // … Observable.fromCallable(new Callable() {
 @Override public String call() throws Exception {Y
 return client.newCall(request).execute();Z
 }X
 }); 
 
 getName()

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Creating Sources Flowable.fromCallable(() -> "Hello");
 
 Observable.fromCallable(() -> "Hello");
 
 Maybe.fromCallable(() -> "Hello");
 
 Single.fromCallable(() -> "Hello");
 
 Completable.fromCallable(() -> "Ignored!");

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Creating Sources Flowable.fromCallable(() -> "Hello");
 
 Observable.fromCallable(() -> "Hello");
 
 Maybe.fromCallable(() -> "Hello");
 Maybe.fromAction(() -> System.out.println("Hello"));
 Maybe.fromRunnable(() -> System.out.println("Hello"))
 
 Single.fromCallable(() -> "Hello");
 
 Completable.fromCallable(() -> "Ignored!");
 Completable.fromAction(() -> System.out.println("Hello"));
 Completable.fromRunnable(() -> System.out.println("Hello"));

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Creating Sources Observable.create();

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Creating Sources Observable.create(new ObservableOnSubscribe() {
 @Override
 public void subscribe(ObservableEmitter e) throws Exception {
 e.onNext("Hello");
 e.onComplete();
 }X
 });

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Creating Sources Observable.create(new ObservableOnSubscribe() {
 @Override
 public void subscribe(ObservableEmitter e) throws Exception {
 e.onNext("Hello");
 e.onComplete();
 }X
 });

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Creating Sources Observable.create(new ObservableOnSubscribe() {
 @Override
 public void subscribe(ObservableEmitter e) throws Exception {
 e.onNext("Hello");
 e.onComplete();
 }X
 });

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Creating Sources Observable.create(new ObservableOnSubscribe() {
 @Override
 public void subscribe(ObservableEmitter e) throws Exception {
 e.onNext("Hello");
 e.onComplete();
 }X
 });

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Creating Sources Observable.create(e -> {
 e.onNext("Hello");
 e.onComplete();
 }); new ObservableOnSubscribe()
 @Override
 public void subscribe(ObservableEmitter ) throws Exception {
 
 
 }X


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Creating Sources Observable.create(e -> {
 e.onNext("Hello"); e.onNext("World");
 e.onComplete();
 });

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Creating Sources OkHttpClient client = // … Request request = // … Observable.create(e -> { client.newCall(request).enqueue(new Callback() { @Override public void onResponse(Response r) throws IOException { e.onNext(r.body().string()); e.onComplete(); }A @Override public void onFailure(IOException e) { e.onError(e); }B });
 }); 
 e.onNext("Hello"); e.onNext("World");
 e.onComplete();

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Creating Sources OkHttpClient client = // … Request request = // … Observable.create(e -> { Call call = client.newCall(request); call.enqueue(new Callback() { @Override public void onResponse(Response r) throws IOException { e.onNext(r.body().string()); e.onComplete(); }A @Override public void onFailure(IOException e) { e.onError(e); }B });
 });

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Creating Sources OkHttpClient client = // … Request request = // … Observable.create(e -> { Call call = client.newCall(request); e.setCancelation(() -> call.cancel()); call.enqueue(new Callback() { @Override public void onResponse(Response r) throws IOException { e.onNext(r.body().string()); e.onComplete(); }A @Override public void onFailure(IOException e) { e.onError(e); }B });
 }); OkHttpClient client = // … Request request = // … Observable.create(e -> { Call call = client.newCall(request); e.setCancelation(() -> call.cancel()); call.enqueue(new Callback() { @Override public void onResponse(Response r) throws IOException { e.onNext(r.body().string()); e.onComplete(); }A @Override public void onFailure(IOException e) { e.onError(e); }B });
 });

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Creating Sources View view = // … Observable.create(e -> { e.setCancelation(() -> view.setOnClickListener(null)); view.setOnClickListener(v -> e.onNext(v));
 }); OkHttpClient client = // ... Request request = // ... Call call = client.newCall(request); e.setCancelation(() -> call.cancel()); call.enqueue(new Callback() { @Override public void onResponse(Response r) throws IOException { e.onNext(r.body().string()); e.onComplete(); }A @Override public void onFailure(IOException e) { e.onError(e); }B });


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Creating Sources Flowable.create(e -> { … }); Observable.create(e -> { … }); Maybe.create(e -> { … }); Single.create(e -> { … }); Completable.create(e -> { … });

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Observing Sources Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Disposable d);
 }B

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Observing Sources Observable Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Observer {
 void onNext(T t);A
 void onComplete();B
 void onError(Throwable t);C
 void onSubscribe(Disposable d);D
 }B interface Disposable {
 void dispose();
 }B interface Subscription {
 void cancel();
 void request(long r);
 }B

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Observing Sources Observable o = Observable.just("Hello"); o.subscribe(new Observer() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … } 
 @Override public void onSubscribe(Disposable d) { ??? }B
 }); Flowable interface Subscriber {
 void onNext(T t);
 void onComplete();
 void onError(Throwable t);
 void onSubscribe(Subscription s);
 }B interface Disposable {
 void dispose();
 }B interface Subscription {
 void cancel();
 void request(long r);
 }B interface T
 T t ;A
 ;B
 ;C
 ;D


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Observing Sources Observable o = Observable.just("Hello"); o.subscribe(new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 }); 
 
 
 
 @Override public void onSubscribe(Disposable d) { ??? }B


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Observing Sources Observable o = Observable.just("Hello"); o.subscribe(new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 });Z // TODO how do we dispose???

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Observing Sources Observable o = Observable.just("Hello"); DisposableObserver observer = new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 } o.subscribe(observer);Z // TODO how do we dispose??????

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Observing Sources Observable o = Observable.just("Hello"); DisposableObserver observer = new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 } o.subscribe(observer);Z observer.dispose();

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Observing Sources Observable o = Observable.just("Hello"); o.subscribe(new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 });Z

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Observing Sources Observable o = Observable.just("Hello"); o.subscribeWith(new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 });Z

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Observing Sources Observable o = Observable.just("Hello"); Disposable d = o.subscribeWith(new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 });Z d.dispose();

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Observing Sources Observable o = Observable.just("Hello"); CompositeDisposable disposables = new CompositeDisposable(); disposables.add(o.subscribeWith(new DisposableObserver() {
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 }));Z disposables.dispose(); 
 
 
 
 d.dispose(); Disposable d =

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Observing Sources Observable o = Observable.just("Hello"); o.subscribeWith(new DisposableObserver() { … });Z Maybe m = Maybe.just("Hello"); m.subscribeWith(new DisposableMaybeObserver() { … });Z Single s = Single.just("Hello"); s.subscribeWith(new DisposableSingleObserver() { … });Z Completable c = Completable.completed(); c.subscribeWith(new DisposableCompletableObserver() { … });Z disposables.add(
 @Override public void onNext(String s) { … }
 @Override public void onComplete() { … }
 @Override public void onError(Throwable t) { … }
 ) disposables.dispose();

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Observing Sources Flowable f = Flowable.just("Hello"); f.subscribeWith(new DisposableSubscriber() { … }); Observable o = Observable.just("Hello"); o.subscribeWith(new DisposableObserver() { … }); Maybe m = Maybe.just("Hello"); m.subscribeWith(new DisposableMaybeObserver() { … }); Single s = Single.just("Hello"); s.subscribeWith(new DisposableSingleObserver() { … }); Completable c = Completable.completed(); c.subscribeWith(new DisposableCompletableObserver() { … }); Flowable f = Flowable.just("Hello"); f.subscribeWith(new DisposableSubscriber() { … }); Observable o = Observable.just("Hello"); o.subscribeWith(new DisposableObserver() { … }); Maybe m = Maybe.just("Hello"); m.subscribeWith(new DisposableMaybeObserver() { … }); Single s = Single.just("Hello"); s.subscribeWith(new DisposableSingleObserver() { … }); Completable c = Completable.completed(); c.subscribeWith(new DisposableCompletableObserver() { … });

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Observing Sources Flowable f = Flowable.just("Hello"); Disposable d1 = f.subscribeWith(new DisposableSubscriber() { … }); Observable o = Observable.just("Hello"); Disposable d2 = o.subscribeWith(new DisposableObserver() { … }); Maybe m = Maybe.just("Hello"); Disposable d3 = m.subscribeWith(new DisposableMaybeObserver() { … }); Single s = Single.just("Hello"); Disposable d4 = s.subscribeWith(new DisposableSingleObserver() { … }); Completable c = Completable.completed(); Disposable d5 = c.subscribeWith(new DisposableCompletableObserver() { … });

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RxJava • A set of classes for representing sources of data. • A set of classes for listening to data sources. • A set of methods for modifying and composing data.

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RxJava • A set of classes for representing sources of data. • A set of classes for listening to data sources. • A set of methods for modifying and composing data.

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Operators • Manipulate or combine data in some way. • Manipulate threading in some way. • Manipulate emissions in some way.

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Operators String greeting = "Hello";

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Operators String greeting = "Hello";Z String yelling = greeting.toUppercase();

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Operators Observable greeting = Observable.just("Hello");Z String yelling = greeting.toUppercase();Y

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Operators Observable greeting = Observable.just("Hello"); Observable yelling = greeting.map(s -> s.toUppercase());Y

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Operators Observable greeting = Observable.just("Hello"); Observable yelling = greeting.map(s -> s.toUppercase());Y

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Operators String greeting = "Hello, World!";

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Operators String greeting = "Hello, World!";Z String[] words = greeting.split(" ");

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Operators Observable greeting = Observable.just("Hello, World!");Z String[] words = greeting.split(" ");Y

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Operators Observable greeting = Observable.just("Hello, World!");Z Observable words = greeting.map(s -> s.split(" "));Y

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Operators Observable greeting = Observable.just("Hello, World!");Z Observable> words = greeting.map(s -> Observable.fromArray(s.split(" ")));Y

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Operators Observable greeting = Observable.just("Hello, World!");Z Observable words = greeting.flatMap(s -> Observable.fromArray(s.split(" ")));Y Observable< > map

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Operators Observable greeting = Observable.just("Hello, World!"); Observable words = greeting.flatMap(s -> Observable.fromArray(s.split(" ")));

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Operators @Override public void success() { runOnUiThread(new Runnable() { @Override public void run() { tv.setText(um.getUser().toString()); }4 }); }A

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Operators Observable user = um.getUser();

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Operators Observable user = um.getUser(); Observable mainThreadUser = user.observeOn(AndroidSchedulers.mainThread());

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Operators Observable user = um.getUser(); Observable mainThreadUser = user.observeOn(AndroidSchedulers.mainThread());

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Operators OkHttpClient client = // … Request request = // … Response response = client.newCall(request).execute();

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); });

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }); Observable backgroundResponse = response.subscribeOn(Schedulers.io());

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }); Observable backgroundResponse = response.subscribeOn(Schedulers.io());

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }); Observable backgroundResponse = response.subscribeOn(Schedulers.io());

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }) .subscribeOn(Schedulers.io());Y

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }) .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread());Y

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }) .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .map(response -> response.body().string());Y

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }) .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .map(response -> response.body().string());Y// NetworkOnMainThread!

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }) .subscribeOn(Schedulers.io()) .map(response -> response.body().string()) // Ok! .observeOn(AndroidSchedulers.mainThread());Y// NetworkOnMainThread!

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Operators OkHttpClient client = // … Request request = // … Observable response = Observable.fromCallable(() -> { return client.newCall(request).execute(); }) .subscribeOn(Schedulers.io()) .map(response -> response.body().string()) // Ok! .flatMap(s -> Observable.fromArray(s.split(" "))) .observeOn(AndroidSchedulers.mainThread());Y// NetworkOnMainThread!

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Operator Specialization Observable

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Operator Specialization first() Observable

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Operator Specialization first() Observable Observable

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Operator Specialization 1 2 3 4 5 6 7 8 9 10 11 first() 1 Observable Observable

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Operator Specialization 1 2 3 4 5 6 7 8 9 10 11 get(0) 1 List List

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Operator Specialization first() Observable Single

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Operator Specialization 1 2 3 4 5 6 7 8 9 10 11 first() 1 Observable Single

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Operator Specialization first() Observable Single NoSuchElementException

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Operator Specialization firstElement() Observable Maybe

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Operator Specialization firstElement() Observable Maybe

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Operator Specialization ignoreElements() Observable Completable

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Operator Specialization 1 2 3 4 5 6 7 8 9 ignoreElements() Observable Completable

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Operator Specialization ignoreElements() Flowable Completable

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Operator Specialization firstElement() Flowable Maybe

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Operator Specialization first() Flowable Single

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Flowable Observable Maybe Single Completable Flowable toObservable() reduce() elementAt() firstElement() lastElement() singleElement() scan() elementAt() first()/firstOrError() last()/lastOrError() single/singleOrError() all()/any()/count() (and more) ignoreElements() Observable toFlowable() reduce() elementAt() firstElement() lastElement() singleElement() scan() elementAt() first()/firstOrError() last()/lastOrError() single/singleOrError() all()/any()/count() (and more) ignoreElements() Maybe toFlowable() toObservable() toSingle() sequenceEqual() toCompletable() Single toFlowable() toObservable() toMaybe() toCompletable() Completable toFlowable() toObservable() toMaybe() toSingle() toSingleDefault() From To

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Flowable Observable Maybe Single Completable Flowable toObservable() reduce() elementAt() firstElement() lastElement() singleElement() scan() elementAt() first()/firstOrError() last()/lastOrError() single/singleOrError() all()/any()/count() (and more) ignoreElements() Observable toFlowable() reduce() elementAt() firstElement() lastElement() singleElement() scan() elementAt() first()/firstOrError() last()/lastOrError() single/singleOrError() all()/any()/count() (and more) ignoreElements() Maybe toFlowable() toObservable() toSingle() sequenceEqual() toCompletable() Single toFlowable() toObservable() toMaybe() toCompletable() Completable toFlowable() toObservable() toMaybe() toSingle() toSingleDefault() From To

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Flowable Observable Maybe Single Completable Flowable toObservable() reduce() elementAt() firstElement() lastElement() singleElement() scan() elementAt() first()/firstOrError() last()/lastOrError() single/singleOrError() all()/any()/count() (and more) ignoreElements() Observable toFlowable() reduce() elementAt() firstElement() lastElement() singleElement() scan() elementAt() first()/firstOrError() last()/lastOrError() single/singleOrError() all()/any()/count() (and more) ignoreElements() Maybe toFlowable() toObservable() toSingle() sequenceEqual() toCompletable() Single toFlowable() toObservable() toMaybe() toCompletable() Completable toFlowable() toObservable() toMaybe() toSingle() toSingleDefault() From To

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Being Reactive um.getUser()

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Being Reactive um.getUser() .observeOn(AndroidSchedulers.mainThread())

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Being Reactive um.getUser() .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new DisposableObserver() { @Override public void onNext(User user) { }1 @Override public void onComplete() { /* ignored */ } @Override public void onError(Throwable t) { /* crash or show */ } });

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Being Reactive um.getUser() .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new DisposableObserver() { @Override public void onNext(User user) { tv.setText(user.toString()); }1 @Override public void onComplete() { /* ignored */ } @Override public void onError(Throwable t) { /* crash or show */ } });2

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Being Reactive disposables.add(um.getUser() .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new DisposableObserver() { @Override public void onNext(User user) { tv.setText(user.toString()); }1 @Override public void onComplete() { /* ignored */ } @Override public void onError(Throwable t) { /* crash or show */ } }));2

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Being Reactive // onCreate disposables.add(um.getUser() .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new DisposableObserver() { @Override public void onNext(User user) { tv.setText(user.toString()); }1 @Override public void onComplete() { /* ignored */ } @Override public void onError(Throwable t) { /* crash or show */ } })); // onDestroy disposables.dispose();

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Being Reactive um.setName("Jane Doe")

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Being Reactive um.setName("Jane Doe") .subscribeOn(Schedulers.io())

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Being Reactive um.setName("Jane Doe") .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread())

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Being Reactive um.setName("Jane Doe") .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new DisposableCompletableObserver() { @Override public void onComplete() { }1 @Override public void onError(Throwable t) { // retry or show }2 });

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Being Reactive um.setName("Jane Doe") .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new DisposableCompletableObserver() { @Override public void onComplete() { // success! re-enable editing }1 @Override public void onError(Throwable t) { // retry or show }2 });3

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Being Reactive disposables.add(um.setName("Jane Doe") .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new DisposableCompletableObserver() { @Override public void onComplete() { // success! re-enable editing }1 @Override public void onError(Throwable t) { // retry or show }2 }));3

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Java 9 • JEP 266: More Concurrency Updates

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Java 9 • JEP 266: More Concurrency Updates Interfaces supporting the Reactive Streams publish-subscribe framework, nested within the new class Flow, along with a utility class SubmissionPublisher that developers can use to create custom components. These (very small) interfaces correspond to those defined with broad participation (from the Reactive Streams initiative) and support interoperability across a number of async systems running on JVMs. Nesting the interfaces within a class is a conservative policy allowing their use across various short-term and long-term possibilities. The proposed java.util.concurrent components have been offered in pre-release since January 2015, and have benefitted from several rounds of review. There are no plans to provide network- or I/O-based java.util.concurrent components for distributed messaging, but it is possible that future JDK releases will include such APIs in other packages.

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final class Flow { private Flow() {} interface Publisher { void subscribe(Subscriber super T> subscriber); } interface Subscriber { void onSubscribe(Subscription subscription); void onNext(T item); void onError(Throwable throwable); void onComplete(); } interface Subscription { void request(long n); void cancel(); } interface Processor extends Subscriber, Publisher { } }

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jakes.link/rx-state

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jakewharton jakewharton jakewharton twitter.com/ github.com/ .com Managing The Reactive World