JEANNE BOYARSKY SOFTWARE DEVELOPER, CODERANCH Coming soon - Java 9 is nearing official release. As Java developers, we should be ready. Java 9 is more than just Jigsaw and we will look at some of the still useful but less talked about features. Some will save you typing and make your code easier to read such as changes to try-with-resources and inner classes. Some are new APIs that will save you time like new stream APIs. Attendees will walk away knowing what’s new and improved in Java 9 regardless of whether they need to complete a jigsaw puzzle.

1. Welcome to Java 9
Spring Days – 6/20/17
Jeanne Boyarsky
https://www.slideshare.net/
boyarsky/2017-java9springdays
Twitter @jeanneboyarsky
Blog: http://www.selikoff.net

2. Modules (Jigsaw)
Problem
• Jar hell
• Solution – Maven/Gradle?
• No closed/private packages
Java 9
• Modules!
Twitter: @jeanneboyarsky

3. Jigsaw – flux
• You can use a command line flag.
• The flag might or might not be the default.
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Do you
• use sun.* internal APIs?
• use a jar that does?

4. • 2011 – Maybe part of Java 7. Nope Plan B
• 2012 - Part of Java 8. No wait
• 2014 - Part of Java 9
• Sept 2016
• May 2017
• July 2017
• Sept 2017?
The Saga of Jigsaw
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5. Moving on
That was nerve wracking.
We clearly need sugar!
Twitter: @jeanneboyarsky

6. Creating a non-empty Set
Set<String> set = new HashSet<>(
Arrays.asList("1","2", "3"));
Set<String> set = Stream.of("1", "2”, "3")
.collect(Collectors.toSet());
Set<String> set = Set.of("1", "2", "3");
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7. For consistency
Map<String, String> map = Map.of("k", "v");
Up to 10 params, then varargs
List<String> list = List.of("1", "2", "3");
Up to 20 params, then varargs
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8. Better Map
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Map<Integer, Integer> map =
Map.ofEntries(
Map.entry(1, 10),
Map.entry(2, 20)
);

9. JavaDoc Search Upgrade
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(to 2017)

10. Try with Resources
Path path = Paths.get("test.txt");
try (BufferedReader reader =
Files.newBufferedReader(path)) {
System.out.println(reader.readLine());
}
Effectively final
resources
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BufferedReader reader =
Files.newBufferedReader(path);
try (reader) {
System.out.println(reader.readLine());
}

11. What’s wrong here?
Connection con =
DriverManager.getConnection(url);
PreparedStatement ps =
con.prepareStatement(sql);
ps.setInt(1, id);
ResultSet rs = ps.executeQuery();
try (con; ps; rs) {
while (rs.next()) {
// process result set
} } Twitter: @jeanneboyarsky
Resource leak!

12. @Deprecated
“Very few deprecated APIs were actually
removed, leading some people to believe that
nothing would ever be removed.
On the other hand, other people believed that
everything that was deprecated might
eventually be removed, which was never the
intent either.”
From JEP 277
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13. @Deprecated New Attributes
Attribute Type Description
forRemoval boolean Is the intent to remove API
from Java at some point?
since String Version of Java when API
first became deprecated (not
populated for all pre-Java 9
APIs)
Twitter: @jeanneboyarsky
Only had for new
APIs before

14. Twitter: @jeanneboyarsky

15. @Deprecated
Warning types
• Ordinary Deprecation
• Removal
@SuppressWarnings("deprecation”)
@SuppressWarnings("removal”)
@SuppressWarnings({"deprecation", "removal"})
Twitter: @jeanneboyarsky

16. What is deprecated for removal?
• Unused code in AWT
• Some old security APIs
• Some thread and runtime APIs
• Some Jigsaw transition modules
(but not classes)
• And…
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17. Applets
Finally deprecated!
But…
forRemoval=false
Applet
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18. Streams - takeWhile
Stream.iterate(entry(1,1),
e -> entry(e.getValue(),
e.getKey()+e.getValue()))
.map(Entry::getValue)
.takeWhile(n -> n < 30)
.forEach(System.out::println);
How print all Fibonacci #s less than 30?
Assumes ordered stream. Takes all elements until
one doesn’t match.
Twitter: @jeanneboyarsky

19. Streams - dropWhile
Stream.iterate(entry(1,1),
e -> entry(e.getValue(),
e.getKey()+e.getValue()))
.map(Entry::getValue)
.dropWhile(n -> n < 30)
.forEach(System.out::println);
How print all Fibonacci #s greater than 30?
Note: This doesn’t work. takeWhile and dropWhile
aren’t always opposites. See why?
Twitter: @jeanneboyarsky

20. Streams - iterate
Stream.iterate(10, i-> i-1)
.limit(10)
.forEach(System.out::println);
Stream.iterate(10, i-> i>0, i-> i-1)
.forEach(System.out::println);
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21. Streams - ofNullable
stream = dubiousObj == null
? Stream.empty()
: Stream.of(dubiousObj);
stream = Stream.ofNullable(dubiousObj);
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22. JShell
• REPL for Java
• Now with tab and up arrow
• More packages known than Nashorn
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23. Random other changes
• Can now have private methods in interfaces
• _ is no longer a legal identifier. Still ok to have
vars like _temp
• sun.misc.Unsafe was replaced by VarHandle. I
can’t imagine needing to do either. Maybe for
low level APIs
• Could use @SafeVarargs on static methods or
final instance methods. Now can do the same
for private instance methods
Twitter: @jeanneboyarsky

24. More new APIs
APIs for reactive programming:
• Flow.Processor
• Flow.Publisher
• Flow.Subscriber
• Flow.Subscription
(new class Flow)
Process APIs
Process.pid()
supportsNormalTermination()
CompletableFuture<Process> onExit()
info()
descendants()
children()
Twitter: @jeanneboyarsky

25. Questions
?
Twitter: @jeanneboyarsky