The document discusses new features in JDK8 including lambdas and functional interfaces, default methods, static interface methods, method references, repeating annotations, extended annotations, Optional, Streams, Date/Time API improvements, Nashorn JavaScript engine, Base64 encoding, jjs and jdepts tools, and Metaspace. Key changes include lambda expressions to write anonymous functions more concisely, default methods to add new methods to interfaces without breaking existing implementations, and functional interfaces to allow lambda expressions to be treated as objects.

1. JDK8
The New Features

2. Language

3. Lambdas and functional
interfaces
new Thread(new Runnable() {
@Override
public void run() {
System.out.println("Hello from thread");
}
}).run();
new Thread(() -> System.out.println("Hello from thread")).run()
@FunctionalInterface
public interface Runnable {
public abstract void run();
}

4. Lambdas and functional
interfaces
Arrays.asList("a", "b", "d").sort((e1, e2) -> e1.compareTo(e2));
Arrays.asList("a", "b", "d").sort(
(String e1, String e2) -> e1.compareTo(e2));
Arrays.asList("a", "b", "d").sort(
(e1, e2) -> {
int result = e1.compareTo(e2);
return result;
});

5. Default methods
interface DefaultInterface {
void show();
default void display() {
System.out.println("Displaying something");
}
}
But … why ??

6. Default methods
package java.lang;
public interface Iterable<T> {
void forEach(Consumer<? super T> action);
}
Core interfaces have new methods
This breaks backwards compatibility
package java.lang;
public interface Iterable<T> {
default void forEach(Consumer<? super T> action) {
for (T t : this) { action.accept(t); }
}
}
This doesn’t

7. Static interface methods
interface MyInterface {
void method1();
static void method2() { System.out.println("Hello from static");
}
}
...
MyInterface.method2();
Keep interface related helper methods in the same class rather
than creating a new one

8. Method references
Static reference
class Example {
public static void main(String[] args) {
String[] str = {"one", "two", "3", "four"};
Arrays.sort(str, Example::compareByLength);
Arrays.sort(str, (s1, s2) -> s1.length() - s2.length());
}
public static int compareByLength(String s1, String s2) {
return s1.length() - s2.length();
}
}

9. Method references
Instance reference
@FunctionalInterface // New JDK8 interface
public interface Supplier {
T get();
}
public String function(Supplier<String> supplier) {
return supplier.get();
}
public void example() {
final String x = "A string";
function(() -> x.toString());
function(x::toString);
}

10. Method references
Constructor reference
class Car {}
class Example {
public static Car createCar(Supplier supplier) {
return supplier.get();
}
public static void repair(Car car) {}
public static void main(String[] args) {
Car car = createCar(Car::new);
List cars = Arrays.asList(car);
cars.forEach(Example::repair);
}
}

11. Repeating annotations
class RepeatingAnnotations {
public @interface Filters { // A hidden filter holder
Filter[] value();
}
@Repeatable(Filters.class)
public @interface Filter {
String value();
}
@Filter("filter1")
@Filter("filter2")
public void filterredMethod() {}
}
Repeat yourself

12. Extended annotations
class Annotations {
public @interface NotEmpty {}
public static class Holder<@NonEmpty T> extends @NonEmpty Object{
public void method() throws @NonEmpty Exception {}
}
public static void main(String[] args) {
final Holder<String> holder = new @NonEmpty Holder<String>();
@NonEmpty Collection<@NonEmpty String> strings =
new ArrayList<>();
}
}
Annotate anything

13. Libraries

14. Optional
Optional<String> name = Optional.ofNullable(null);
System.out.println("Name is set? " + name.isPresent() );
System.out.println("Name: " + name.orElseGet( () -> "[none]" ));
System.out.println(name.map( s -> "Hey " + s + "!" )
.orElse("Hey Stranger!"));
java.util.Optional
Name is set? false
Name: [none]
Hey Stranger!

15. Streams
for (Student student : students) {
if (student.getName().startsWith("A")){
names.add(student.getName());
}
}
java.util.stream
List<string> names =
students.stream()
.map(Student::getName)
.filter(name -> name.startsWith("A"))
.collect(Collectors.toList());
The old way
The Java8 way

16. Streams
java.util.stream
int sum =
students.parallelStream()
.map(Student::getName)
.filter(name -> name.startsWith("A"))
.mapToInt(String::length)
.sum();
System.out.println(
Arrays.asList("One", "Two", "Three")
.stream().collect(Collectors.groupingBy(String::length))
);
{3=[One, Two], 5=[Three]}

17. Date/Time API
JSR 310 - java.time

18. Date/Time API
JSR 310 - java.time
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR, cal.get(Calendar.HOUR) + 2);
LocalTime now = LocalTime.now();
LocalTime later = now.plus(2, HOURS);
The old way
The Java8 way

19. Nashorn
JavaScript engine
• Rhino replacement
• Faster (2 to 10x performance boost)
• Full ECMAScript 5.1 support + extensions
• Compiles JS to Java bytecode

20. Nashorn
Example
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("JavaScript");
System.out.println(engine.getClass().getName() );
System.out.println("Result:" + engine.eval(
"function f() { return 1; }; f() + 1;" ) );
jdk.nashorn.api.scripting.NashornScriptEngine
Result: 2

21. Nashorn
Performance
V8 Chrome 31
Spidermonkey F
F 25.0.1
Nashorn
Octane 2.0 14 474 10 066 9 307
Sunspider 1.0.2 220.8 ms 246.5 ms 256.2 ms
http://wnameless.wordpress.com/2013/12/10/javascript-engine-benchmarks-nashorn-vs-v8-vs-spidermonkey/

22. Base64
Finally … java.util.Base64
final String encoded = Base64
.getEncoder()
.encodeToString( text.getBytes( StandardCharsets.UTF_8 ));
final String decoded = new String(
Base64.getDecoder().decode(encoded),
StandardCharsets.UTF_8);

23. Tools

24. jjs
function f() {
return 1;
};
print(f() + 1);
jjs file.js
2
file.js
command
output
Nashorn runner

25. jdepts
Dependency analyzer
jdeps jdom2-2.0.5.jar
jdom2-2.0.5.jar ->
/Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home/jre/lib/
rt.jar
org.jdom2 (jdom2-2.0.5.jar)
-> java.io
-> java.lang
-> java.net
-> java.util
-> java.util.concurrent
org.jdom2.adapters (jdom2-2.0.5.jar)
-> java.lang
-> java.lang.reflect
-> javax.xml.parsers
…
command
output

26. JVM
Metaspace

27. Thank you :)