Cleaner Code [email protected] 

Using Java 8 features in Android 

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Using Java 8 features in Android Retrolambda https://github.com/evant/gradle- Gradle Retrolambda Plugin https://github.com/orfjackal/retrolambda StreamSupport Library http://sourceforge.net/projects/streamsupport/ 

Lambdas & Streams
 inside
 Android 

What are lambdas? 

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Classic Java 7 Interface Implementation ErrorDialog.build().onOk(new DialogListener() { @Override public void onPress(Button b) { router.displayScene(b,TopicsScene.class); } }).onCancel(new DialogListener()
 { @Override public void onPress(Button b) { router.displayScene(b,TopicsScene.class); } }); 

Classy Java 8 Lambda implementation ErrorDialog.build() .onOK( b -> router.displayScene(b,TopicsScene.class)) .onCancel( b -> router.displayScene(b,TopicsScene.class)); 

Java 7 with Observables reloadAndStore(key).subscribe(new Action1() { @Override public void call(V v) { log.debug("Reloaded item with key={}", key); } }, new Action1() { @Override public void call(Throwable e) { log.error("Error reloading key={} to store={}", key, DataStore.this.getClass().getName(), e); } }); 

Java 8 with Observables reloadAndStore(key) .subscribe(v -> log.debug("Reloaded item with key={}", key), e -> log.error("Error reloading key={} to store={}", key, DataStore.this.getClass().getName(), e)); 

Lambdas implement the interface behind the scene reloadAndStore(key) .subscribe(v -> log.debug … reloadAndStore(key).subscribe(new Action1() { @Override public void call(V v) { log.debug("Reloaded item with key={}", key); } } 

Java 8 Streams 

Using Java 8 Streams import java8.util.stream.StreamSupport; public class MyClass { public void tryMe() { List aList = new ArrayList<>(); aList.add(new Random().nextInt()); aList.add(new Random().nextInt()); aList.add(new Random().nextInt()); StreamSupport.stream(aList) .map(el -> el.hashCode()) .forEach(el-> Log.d("SERVICE", String.valueOf(el))); } } 

Using Java 8 Streams List myList = Arrays.asList("a1", "a2", "b1", "c2", "c1"); StreamSupport .stream(myList) .filter(s -> s.startsWith("c")) .map(String::toUpperCase) .sorted() .forEach(v -> logger.d(v)); // C1 // C2 

Using Groovy in Android 

Using Groovy in Android Groovy Android Gradle Plugin https://github.com/groovy/groovy-android-gradle- 

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Groovy in Android - Why? • Pure functional language, perfect for writing compact code in logical workflows.
 • Hides even more boilerplate code then Java 8.
 • Toolbox with built in support for lambdas, streams, 
 json-parsing and much much more .. 

Groovy in Android - Why? • You can mix both Java and Groovy classes in the code tree (live side by side). • Java can access Groovy classes and vice versa. • You already using it. Gradle is written in Groovy 

Classic Java 7 Interface Implementation ErrorDialog.build().onOk(new DialogListener() { @Override public void onPress(Button b) { router.displayScene(b,TopicsScene.class); } }).onCancel(new DialogListener()
 { @Override public void onPress(Button b) { router.displayScene(b,TopicsScene.class); } }); 

A Groovy Interface Implementation ErrorDialog.build() .onOK({ b -> router.displayScene(b,TopicsScene.class)}) .onCancel({ b -> router.displayScene(b,TopicsScene.class)}); 

Groovy with “streams” def myList = ["a1", "a2", "b1", "c2", “c1”]; myList .findAll(s -> s.startsWith("c")) .collect(s -> s.toUpperCase()) .sort() .each(s -> println s); // C1 // C2 

Declarations - Java 7 vs Groovy def myList = ["a1", "a2", "b1", "c2", “c1”] List myList = Arrays.asList("a1", "a2", "b1", "c2", "c1"); 

Declarations - Java 7 vs Groovy def myText = “““
 
 This
 is
 some
 text!
 
 “““ String myText = “\n\nThis\nis\nsome\ntext!\n”; 

Closures = Anonymous code def someCode = { 
 def n = 1; println n; } someCode() 

Closures = Anonymous code methodA(someCode) def methodA(code) { 
 methodB(code)
 } def methodB(code) { 
 code()
 } 

Json Slurper { "staff":[ { "name":"Bob", "title":"Coder" }, { "name":"Steve", "title":"Boss" }, { "name":"Tim", "title":"Coder" } ] } def json = JsonSlurper().parse(text); json.staff[0].name // Bob json.staff // Array of staff json.staff.find{s-> s.name == “Steve”} json.staff.findAll{t->t.title == “Coder”} json.staff.title.unique().sort() Boss, Coder 

Questions?