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It took 19 years of madness Calendar calendar = GregorianCalendar.getInstance(); calendar.set(2014, 4, 15, 0, 0, 0); ! calendar.getTime(); // => Thu May 15 00:00:00 CEST 2014 ! calendar.getTime().getYear(); // => 114

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Joda showed the way for almost 10 years LocalDate today = new LocalDate(2014, 5, 15); ! today.toString("MMM dd, yyyy”); // => May 15, 2014

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That’s all it took ..

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.. to get a
 Date and Time API LocalDate today = LocalDate.of(2014, 5, 15); ! today.getMonth(); // => MAY ! LocalDate tomorrow = today.plusDays(1); tomorrow.getDayOfMonth(); // => 16 ! today.getDayOfMonth(); // => 15

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Adjusters LocalDate today = LocalDate.now(); ! today.with(firstDayOfMonth()); // => 2014-05-01 ! today.with(lastDayOfMonth()); // => 2014-05-31 ! today.with(lastInMonth(TUESDAY)); // => 2014-05-27

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Timezones ZoneId amsterdam = ZoneId.of("Europe/Amsterdam"); ZoneId chicago = ZoneId.of("America/Chicago"); ! ZonedDateTime now = ZonedDateTime.now(amsterdam); // => 2014-05-15T19:00:03.557+02:00[Europe/Amsterdam] ! now.withZoneSameInstant(chicago); // => 2014-05-15T12:00:03.557-05:00[America/Chicago] ! now.withZoneSameLocal(chicago); // => 2014-05-15T19:00:03.557-05:00[America/Chicago]

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Misc Information Year year = Year.now(); year.getValue(); // => 2014 ! year.isLeap(); // => false ! year.length(); // => 365

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Just a bit of madness left DateTimeFormatter formatter =
 DateTimeFormatter.ofPattern("MMM dd, yyyy"); ! LocalDate today = LocalDate.of(2014, 5, 15); ! today.format(formatter); // => May 15, 2014

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Repeatable Annotations @Example("java 8") @Example("annotations") class Java8AnnotationExamples { .. } ! Java8AnnotationExamples.class.getAnnotationsByType( Example.class) // => [@Example(value=java 8),
 @Example(value=annotations)]

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How it works @Repeatable(Examples.class) public @interface Example { String value(); } ! public @interface Examples { Example[] value(); }

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PermGen eden to from tenured PermGem

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Metaspace eden to from tenured Metaspace

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Garbage Collection -XX:MetaspaceSize= -XX:MaxMetaspaceSize=

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Depletion ! static Map leaks = new HashMap<>(); ! for (int i = 0; i < iterations; ++i) { String fakeJar = "file:" + i + ".jar"; URLClassLoader uniqueClassLoader =
 createClassLoader(fakeJar); Leak leak = (Leak) Proxy.newProxyInstance(
 uniqueClassLoader, new Class>[] { Leak.class }, new LeakInvocationHandler()); leaks.put(fakeJar, leak); }

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PermGen Depletion $ java_home 1.7 -exec java \
 KlassLeaker --iterations 50000
 
 java.lang.OutOfMemoryError: PermGen space

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Metaspace Depletion $ java_home 1.8 -exec java \
 KlassLeaker --iterations 50000
 
 Done

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Metaspace Depletion $ java_home 1.8 -exec java -XX:MaxMetaspaceSize=128m \
 KlassLeaker --iterations 50000
 
 java.lang.OutOfMemoryError: Metaspace

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Nashorn $ java_home 1.8 -exec jjs jjs> print('Hello, World!')
 Hello, World! ! jjs> var plus = function(acc, n) { return acc + n } jjs> [1,2,3].reduce(plus)
 6 !

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Actual JavaScript
 (no ints) jjs> typeof 1
 number ! jjs> ['1','1','1'].map(parseInt)
 1,NaN,1 ! jjs> [1,2,3].map(parseInt)
 1,NaN,NaN

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Java Interoperability jjs> var Date = Java.type('java.time.LocalDate') ! jjs> var today = Date.now() jjs> today
 2014-05-15 ! jjs> today.year
 2014 !

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But… jjs> var IntStream = \
 Java.type(‘java.util.stream.IntStream’) ! jjs> var Range = IntStream.range jjs> Range(1,10).toArray()
 [I@78b729e6 !

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JavaScript Libraries jjs> load(‘http://cdnjs.cloudflare.com/ajax/libs/ underscore.js/1.6.0/underscore-min.js') ! jjs> var range = Range(1, 6).toArray() jjs> _.inject(range,
 function(acc, n) { return acc * n })
 120 jjs> 


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ScriptEngine ScriptEngineManager factory =
 new ScriptEngineManager(); ScriptEngine nashorn =
 factory.getEngineByName("nashorn"); ! nashorn.eval(“function now() { return new Date }“); ! Invocable invocable = (Invocable) nashorn; invocable.invokeFunction(“now") // => [Date 2014-05-15T17:00:03.557Z]

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Using JavaScript libraries from Java nashorn.eval("load('http://cdnjs.cloudflare.com/ajax/ libs/underscore.js/1.6.0/underscore-min.js')"); ! nashorn.eval("function underscore() { return _ }"); ! Object underscore =
 invocable.invokeFunction("underscore"); invocable.invokeFunction(underscore, “head", new int[] { 1,2,3,4,5 }); // => 1

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“Functions” as Anonymous Objects writeToFile("todo.txt", new FileWriteFunction() { @Override public void apply(Writer file) throws IOException { file.write("learn about lambdas\n"); file.write("learn stream API\n"); } })

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Lambdas writeToFile("todo.txt", file -> { file.write("learn about lambdas\n"); file.write("learn stream API\n"); })

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Closures String todoList = "learn about lambdas\n" + "learn stream API\n"; ! writeToFile("todo.txt", file -> { file.write(todoList); })

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Just a spoonful of Syntactic Sugars? public class Lambdas { public void run(Function fn) { System.out.println(fn.apply()); } ! public static void main(String[] args) { new Lambdas().run( () -> "Hello, World!"); } }

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Just a spoonful of Syntactic Sugars? $ java_home 1.8 -exec javap -p Lambdas
 Compiled from "Lambdas.java"
 public class Lambdas {
 public Lambdas();
 public void run(Function);
 public static void main(java.lang.String[]);
 private static java.lang.String lambda$main$0();
 }

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How it works $ java_home 1.8 -exec javap -c Lambdas
 
 public static void main(java.lang.String[]);
 Code:
 0: new #6 // class Lambdas
 3: dup
 4: invokespecial #7 // Method "":()V
 7: invokedynamic #8, 0 // InvokeDynamic #0:apply: ()LFunction;
 12: invokevirtual #9 // Method run:(LFunction;)V
 15: return

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java.util.stream.Stream Collection.stream() ! -> filter :: [a] -> (a->Boolean) -> [a] ! -> map :: [a] -> (a->b) -> [b] ! -> reduce :: [a] -> r -> (r->a->r) -> r ! -> collect :: [a] -> ([a]->b) -> b

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Making (more) sense of Collections range(1,6).stream() .count() // => 5 .reduce(0, (acc, n) -> acc * n ) // => 120 .map( n -> n * n ).collect(toList()) // => [1,4,9,16,25] .filter( n -> n % 2 == 0 ).collect(toList()) // => [2,4]

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Optional interface UserStore { Optional find(Long id); } ! Optional user = userStore.find(1L); ! String lastname = user.map(User::getLastname) .orElse(""); ! user.ifPresent(passwordReset::send);

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Higher-Order Functions Function1 complement(
 Function1 fn) { return t -> ! fn.apply(t); } ! Function1 adult = n -> n >= 18; Function1 child = complement(adult); adult.apply(21); // => true child.apply(21); // => false

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Default Implementation public interface Collector { ! boolean isEmpty(); ! default boolean nonEmpty() { return ! isEmpty(); } }

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Parallel range(1,50_000).parallel() .filter(Numbers::isPrime) .count()

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Parallel forkJoinPool.submit(() -> range(1,50_000).parallel() .filter(Numbers::isPrime) .count() ).get()

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java.util.Base64 Base64.Encoder encoder = Base64.getEncoder(); Base64.Decoder decoder = Base64.getDecoder(); ! String input = "Hello, World!"; byte[] base64 =
 encoder.encode(input.getBytes("UTF-8")); ! new String(base64, "UTF-8"); // => SGVsbG8sIFdvcmxkIQ== ! new String(decoder.decode(base64), "UTF-8"); // => Hello, World! !

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