The document discusses the new features in Java 8, including improvements in concurrency with new classes like LongAdder and StampedLock, support for functional programming through default methods, functional interfaces, and lambda expressions, as well as the introduction of streams for processing collections. It also highlights the enhancements in date/time handling and optional types. The document concludes with information on downloading JDK 8 and IDE support for it.

1. What’s new in Java 8
Kyle Smith
linkedin.com/in/kylesm
@kylesm

2. • Concurrency improvements
• Default methods
• Functional interfaces
• Lambda expressions
• Method references
• Streams
• Date/time
• Optional
• JavaScript
• JVM PermGen
• Base64 support
• Compact profiles
• Annotation improvements
• Type inference improvements
• Method parameter reflection
• JDBC 4.2

3. • Concurrency improvements
• Default methods
• Functional interfaces
• Lambda expressions
• Method references
• Streams
• Date/time
• Optional
• JavaScript
• JVM PermGen
• Base64 support
• Compact profiles
• Annotation improvements
• Type inference improvements
• Method parameter reflection
• JDBC 4.2

4. Themes

9. • ConcurrentHashMap — all new (inside)!
• LongAdder, DoubleAdder
• StampedLock
• CompletableFuture

10. Adders

11. • New classes for concurrent counters
• Waaaayyy more scalable than AtomicLong,etc.
• …if you can tolerate some inaccuracy

12. LongAdder clicks = new LongAdder();
clicks.increment();
// or counter.add(long)
// ...
clicks.sum();

14. StampedLock

15. • Alternative to ReentrantReadWriteLock
• “does not consistently prefer readers over writers or
vice versa"
• Provides optimistic reads

16. void move(double deltaX, double deltaY){
long stamp = sl.writeLock();
try {
x += deltaX;
y += deltaY;
} finally {
sl.unlockWrite(stamp);
}
}

17. double distanceFromOrigin() {
long stamp = sl.tryOptimisticRead();
double currentX = x, currentY = y;
if (!sl.validate(stamp)) {
stamp = sl.readLock();
try {
currentX = x;
currentY = y;
} finally {
sl.unlockRead(stamp);
}
}
return Math.sqrt(currentX * currentX
+ currentY * currentY);
}

18. CompletableFuture

19. • Everybody wants to be event-driven & reactive
• CompletableFuture allows composition of async
work

20. CompletableFuture<String> f1 = //…
CompletableFuture<Double> f2 = f1
.thenApply(Integer::parseInt)
.thenApply(r -> r * r * Math.PI);

21. Default methods

22. • Interfaces can supply non-abstract methods
• Enables existing interfaces to evolve
• Eliminates the need for companion (“garbage”)
classes

23. // java.lang.Iterable
default void forEach(Consumer<? super T>
action) {
Objects.requireNonNull(action);
for (T t : this) {
action.accept(t);
}
}

24. Functional interfaces

25. • Any interface with a single abstract method
• Examples:
• java.util.Comparator
• java.lang.Runnable
• Can be annotated with @FunctionalInterface

26. Lambda expressions

27. • Function values in Java
• Compatible with a functional interface when their
shapes match
• Syntax: (parameters) -> expression

28. DoubleUnaryOperator op1 =
(double r) -> r * r * Math.PI;
DoubleUnaryOperator op2 =
(r) -> r * r * Math.PI;
Runnable r =
() -> System.out.println("Hi, NEJUG!");
void cut(List<String> l, int len) {
l.replaceAll(s -> s.substring(0, len));
}

29. Streams

30. public Collection<Person>
findStudents(List<Person> people) {
Collection<Person> students =
new ArrayList<>();
for (Person p : people) {
if (p.isStudent()) {
students.add(p);
}
}
return students;
}

31. public Collection<Person>
findStudents(List<Person> people) {
Collection<Person> students =
new ArrayList<Person>();
people.forEach(i -> {
if (i.isStudent()) {
students.add(i);
}
});
return students;
}

32. public Collection<Person>
findStudents(List<Person> people) {
return people
.stream()
.filter(p -> p.isStudent())
.collect(Collectors.toList());
}

33. • “ A sequence of elements on which one or more
operations can be performed”
• Operations are either intermediate or terminal
• Streams can be sequential or parallel

34. • Intermediates:
• map, filter, flatMap, sorted, allMatch, anyMatch,
findAny, findFirst, flatMap, …
• Terminal:
• collect, count, forEach,reduce, max, min, …

35. long count = values
.stream()
.sorted()
.count();
long count = values
.parallelStream()
.sorted()
.count();

36. What next?
• Download JDK 8 from java.oracle.com
• IDE Support:
• Eclipse 4.3.2 SR2 (with patches!)
• IntelliJ IDEA 12.0+
• NetBeans IDE 8.0

37. Can’t move to Java 8?
• Google Guava (Java 6+)
• jsr166e (Java 6+)
• CHMv8, F/J tweaks, StampedLock, etc.
• Mix in some Groovy
• GPars

38. References:
http://bit.ly/1fRGyQV