1. What`s New in Java 8
Mohsen Zainalpour
zainalpour@yahoo.com
JUG
2. JDK 8
Schedule and status
•
•
•
•
•
•
•
•
•
•
2012/04/26
2012/06/14
2012/08/02
2012/09/13
2012/11/29
2013/01/31
2013/06/13
2013/09/05
2014/01/23
2014/03/18
M1
M2
M3
M4
M5
M6
M7 Feature Complete
M8 Developer Preview
M9 Final Release Candidate
GA General Availability
3. Agenda
Major changes
1
Why is Java still changing?
2
Lambda Project
3
Date and Time API
4
Type Annotations
5
Compact Profiles
JUG
4. Java 8 Is Revolutionary, Java Is Back
“Lambda is the single largest upgrade to the programming
model. Ever. It's larger even than Generics. It's the first time
since the beginning of Java that we've done a carefully
coordinated co-evolution of the virtual machine, the language
and the libraries, all together. Yet the result still feels like
Java. Mark Reinhold (Chief Architect of the Java Platform Group at Oracle)
5. Java 8 Is Revolutionary, Java Is Back
“Lambda is the single largest upgrade to the programming
model. Ever. It's larger even than Generics. It's the first time
since the beginning of Java that we've done a carefully
coordinated co-evolution of the virtual machine, the language
and the libraries, all together. Yet the result still feels like
Java. Mark Reinhold (Chief Architect of the Java Platform Group at Oracle)
14. Why is Java still changing?
The changing computing background
big data
multicore
cloud
computing
Increasingly dealing with big data (terabytes and up) and wishing to exploit
multicore computers or computing clusters effectively to process this.
And this means using:
parallel processing
15. The Progress of Programming
There`s been a lot of progress
&
Progress is being allowed to forget things!
16. The Progress of Programming
There`s been a lot of progress:
- Assemblers let us forget opcodes
17. The Progress of Programming
There`s been a lot of progress:
- Assemblers let us forget opcodes
- Garbage collections let us forget memory management
#include <stdio.h>
#include <stdlib.h>
int main () {
…
buffer = (char*) malloc (i+1);
…
free (buffer);
…
}
19. Why Can`t We Forget About Parallelism?
Most of parallelism problems are doing bulk operations on
collection
and we keep writing code like this:
int sum = 0;
for (int i = 0; i < a.length; i++) {
sum += a[i];
}
It is inherently serial
20. Why Can`t We Forget About Parallelism?
If the processing of different elements is to proceed in
parallel, it is the responsibility of the client code
21. Why Can`t We Forget About Parallelism?
If the processing of different elements is to proceed in parallel, it is the responsibility
of the client code
n1
n2
n3
sum1
n4
n5
n6
n7
sum2
n8
n9
…
…
sum3
…
…
sum4
22. Why Can`t We Forget About Parallelism?
If the processing of different elements is to proceed in parallel, it is the responsibility
of the client code
n1
n2
n3
sum1
n4
n5
n6
n7
sum2
n8
n9
…
…
…
…
sum3
class Sum implements Callable<Long> {
private final long from;
private final long to;
Sum(long from, long to) {
this.from = from;
this.to = to;
}
public Long call() {
long acc = 0;
for (long i = from; i <= to; i++) {
acc = acc + i;
}
return acc;
}
}
sum4
23. Why Can`t We Forget About Parallelism?
If the processing of different elements is to proceed in parallel, it is the responsibility
of the client code
n1
n2
n3
sum1
n4
n5
n6
n7
sum2
n8
n9
…
…
sum3
…
…
sum4
ExecutorService executor = Executors.newFixedThreadPool(2);
List<Future<Long>> results = executor.invokeAll(asList(
new Sum(1,
250),
new Sum(251, 500),
new Sum(551, 750),
new Sum(751, 1000)
));
for (Future<Long> result : results) {
System.out.println(result.get());
}
24. Why Can`t We Forget About Parallelism?
Sequential
Thread 1
Parallel
(assuming a
quad core
machine)
Thread 1
Thread 2
Thread 3
Thread 4
Time t
Done
parallel
Done
sequential
25. Why Can`t We Forget About Parallelism?
Let the Library Writers do it!
Collection developers know the recursive structure of their data
But right now they can`t use that knowledge
26. Why Can`t We Forget About Parallelism?
Let the Library Writers do it!
Collection developers know the recursive structure of their data
But right now they can`t use that knowledge
int sum = 0;
for (Iterator<Integer> itr = myList.iterator();itr.hasNext(); ) {
sum += itr.next();
}
The problem is external iteration
27. Why Can`t We Forget About Parallelism?
Internal Iteration
Instead of this:
int sum = 0;
for (int i=0;i<myList.size();i++){
int a=myList.get(i);
sum+=a;
}
28. Why Can`t We Forget About Parallelism?
Internal Iteration
Instead of this:
We`re going to write this:
int sum = 0;
int [] sum = new int[1];
for (int i=0;i<myList.size();i++){
int a=myList.get(i);
sum+=a;
}
myList.forEach(
…
);
29. Why Can`t We Forget About Parallelism?
Internal Iteration
Instead of this:
We`re going to write this:
int sum = 0;
int [] sum = new int[1];
for (int i=0;i<myList.size();i++){
int a=myList.get(i);
sum+=a;
}
myList.forEach(
…
);
• Let the collection choose its iteration strategy
- Parallel, serial, out-of-order, lazy, …
30. Why Can`t We Forget About Parallelism?
Internal Iteration
Instead of this:
We`re going to write this:
int sum = 0;
int [] sum = new int[1];
for (int i=0;i<myList.size();i++){
int a=myList.get(i);
sum+=a;
}
myList.forEach(
a -> sum[0]+=a
);
• Let the collection choose its iteration strategy
- Parallel, serial, out-of-order, lazy, …
31. Why Can`t We Forget About Parallelism?
a ->
sum[0]+=a
32. Lambda Project – JSR 335
JSR 335 (Lambda Project) aims to support
programming in a
multicore environment
by adding closures and related features to
the Java language.
33. What are Lambda Expressions (closures)?
A lambda expression :
34. What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
35. What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
a ->
having an
argument
list
36. What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
a return
type
a ->
having an
argument
list
37. What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
a return
type
a ->
having an
argument
list
and a body
sum[0]+=a
38. What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
having an
argument
list
a return
type
and a body
and able to refer to values from the enclosing scope (closure)
a ->
sum[0]+=a
39. What are Lambda Expressions (closures)?
A lambda expression :
is an
anonymous
method
having an
argument
list
To pass behavior to the API as data
a return
type
and a body
and able to refer to values from the enclosing scope (closure)
a ->
sum[0]+=a
41. From Single Method Interface ….
public interface Comparator<T> {
int compare(T o1, T o2);
}
42. From Single Method Interface ….
public interface Comparator<T> {
int compare(T o1, T o2); Single Abstract Method (SAM)
}
43. From Single Method Interface ….
public interface Comparator<T> {
int compare(T o1, T o2); Single Abstract Method (SAM)
}
Functional Interface
44. From Single Method Interface ….
public interface Comparator<T> {
int compare(T o1, T o2);
}
Collections.sort(strings, new Comparator<String>()
{
public int compare(String s1, String s2) {
return s1.compareToIgnoreCase(s2);
}
});
45. From Single Method Interface ….
public interface Comparator<T> {
int compare(T o1, T o2);
}
Collections.sort(strings, new Comparator<String>()
{
public int compare(String s1, String s2) {
return s1.compareToIgnoreCase(s2);
}
});
46. From Single Method Interface ….
public interface Comparator<T> {
int compare(T o1, T o2);
}
Collections.sort(strings, new Comparator<String>()
{
public int compare(String s1, String s2) {
return s1.compareToIgnoreCase(s2);
}
});
Bulky syntax
Confusion surrounding the meaning of names and this
47. … To Lambda Expressions
Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2));
48. … To Lambda Expressions
Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2));
49. … To Lambda Expressions
Collections.sort(strings, (s1, s2) -> s1.compareToIgnoreCase(s2));
Lambda expression are always converted to
instance of a functional interface
Comparator<String> c = (s1, s2) -> s1.compareToIgnoreCase(s2));
No need of changing the JVM to create a new
type for lambda expressions
50. … To Lambda Expressions
Collections.sort(strings,
new Comparator<String>() {
public int
compare(String s1, String s2)
{
return
s1.compareToIgnoreCase(s2);
}
});
Collections.sort(strings,
(s1, s2) ->
s1.compareToIgnoreCase(s2)
);
51. … To Lambda Expressions
Collections.sort(strings,
new Comparator<String>() {
public int
compare(String s1, String s2)
{
return
s1.compareToIgnoreCase(s2);
}
});
Collections.sort(strings,
(s1, s2) ->
s1.compareToIgnoreCase(s2)
);
52. Without more language support
for parallel idioms,
people will instinctively reach for
serial idioms
56. Parallel Streams
A behavioral parameter (lambda) may be invoked concurrently
– This constraint gives us “wiggle room” to optimize
57. Up the level of abstraction
External iteration conflates what with how
Internal iteration: more what; less how
Client passes behavior to the API as data
Library is free to use
Multiple
threads
Out-oforder
execution
Laziness
58. Lambdas in Java 8
Code as
data
(Simplicity)
Bulk data
operations
Lambda
Interface
evolution
Multi-core
processing
/ parallel
processing
61. New Date and Time API
History of Java Date/Time APIs
Java.util.Date, java.util.Calendar
- Strong candidates for the all-time worst Java platform library
design
Joda Time
- Quality date and time library
JSR-310
- Builds on experience of Joda Time
62. New Date and Time API
Design Principles
Immutable
- Thread-safe, allows caching
Fluent
- easy to read, like a DSL
LocalDate.of(2013,Month.JANUARY,09).withYear(2014);
63. New Date and Time API
Time for Humans
Field-base, designed for humans
- Year,month,day,hour,minute,second
- LocalDate,LocalDateTime,ZonedDateTime,Period …
64. New Date and Time API
Los Angeles
16:20
London
12:50
65. New Date and Time API
void flightTime()
{
LocalDate date = LocalDate.of(2013, Month.SEPTEMBER, 14);
LocalTime takeoff = LocalTime.of(12, 50);
LocalTime landing = LocalTime.of(16, 20);
ZoneId LHR = ZoneId.of("Europe/London");
ZoneId SFO = ZoneId.of("America/Los_Angeles");
Duration flightTime = Duration.between(
ZonedDateTime.of(date, takeoff, LHR),
ZonedDateTime.of(date, landing, SFO));
System.out.println("Flight time: " + flightTime);
}
67. Type Annotations
JSR-308 brings annotations on Type use
Are an enabler for the checkers framework
Ex.:
new @Interned MyObject();
myString = (@NonNull String) myObject;
void monitorTemperature() throws
@Critical TemperatureException { ... }
71. Java SE 8 Compact Profiles
SE 8 Compact
Profiles
3
SE Full JRE
Optional Components
UI & Toolkits
2
Compact3 Class libraries
Integration Libraries
Compact2 Class libraries
Other Base Libraries
Base Compact1 Classes
Lang & Util Base Libraries
Hotspot VM
Hotspot VM
1
