1. Adopt OpenJDK
Hackathon, 11 Dec. 2014

2. Agenda of the hackathon
 Build OpenJDK
 Improve OpenJDK
 Write some tests
 Create patch
 Submit patch

3. Agenda of the hackathon
 Build OpenJDK
 Improve OpenJDK
 Write some tests
 Create patch
 Submit patch
 While building…
◦ Intro to OpenJDK

4. Let’s get it going
 Import VM and login
 Change to openjdk directory
cd $SOURCE_CODE/jdk9
 Get the sources
bash get_sources.sh
 Configure
bash configure
 Make images
make clean images

5. OpenJDK overview
 Free and open-source implementation of
the Java Platform, Standard Edition
 Base for the Oracle VM
 GPL v2 for the VMs and GPL v2 +
classpath exception for class libraries
 Major contributors:
◦ IBM
◦ Apple
◦ RedHat
◦ SAP
◦ A lot of JUGs

6. Why bother?
 Move Java forward
 Give back something to the platform
 Help our JUG gain its own identity and
focus
 Acquire new knowledge
 Have some fun and socialize

7. How can we help?
 Introductory level
◦ Fix compiler warnings
◦ Generify, coinify and labdify internal APIs
◦ Add new tests, convert existing tests
◦ Fix typos, add javadoc
 Next level
◦ Affiliate with an existing project (Jigsaw,
Nashorn)
◦ Help with new stuff in project Valhalla

8. Development process
 Sign OCA
 Find interesting bug or enhancement
 Discuss with sponsoring project
mailing list
 Get together and create a patch
◦ Don’t forget the tests!
 Upload the patch and contact ML
again
 Be proud of yourself!

9. Task selection (1)
 Add getStackTraceString() to
Throwable
 Usually people do:
catch (MyException e) {
StringWriter sw = new StringWriter();
e.printStackTrace(
new PrintWriter(sw));
}
 Look at existing solutions (Apache
Commons)
 https://bugs.openjdk.java.net/browse/JD
K-5050783

10. Task selection (2)
 Generic support to Collection bulk
methods
 addAll, containsAll, removeAll,
retainAll can only receive other
collections
 You have to an intermediate
Arrays.asList:
collection.addAll(Arrays.asList("a", "b",
"c"));
 Consider using default methods
 https://bugs.openjdk.java.net/browse/J
DK-6201180

11. Task selection (3)
 Replace array parameters with
varargs
 Look throughout all internal APIs
 Supported since JDK 1.5
 Discuss with Joe Darcy and team
 https://bugs.openjdk.java.net/browse/J
DK-4974893

12. Write some tests
 JTreg: the legacy
◦ Java program with main method
◦ If test fails, testcase should throw an exception
◦ If it succeeds, testcase should return normally
/* @test
* @summary StringBuffer.isEmpty();
* @run main IsEmptyTest
*/
public class IsEmptyTest {
public static void main(String[] args) {
StringBuffer buffer = new StringBuffer();
if (!buffer.isEmpty()) {
throw new RuntimeException("StringBuffer isEmpty on new
object failed");
}
}
}

13. Test “docklets”
@test – defines a test. Mandatory.
@run – tells how to perform a test.
@summary – text description.
@library – reference library source files.
@build – compile class or library before
running test
@bug – bug number reference
@key – keywords

14. TestNG support
 TestNG is cool and nicely supported
 TestNG test cases are run through jtreg
 Two types of tests
 Type 1
◦ Describe the test in JTreg “docklets”
◦ No main method required
/* @test
* @summary comments about your test;
* @run testng YourTest
*/
 Type 2
◦ Describe the test in TEST.ROOT or TESTS.properties
TestNG.dirs = .
othervm.dirs = tck/java/time/chrono
test/java/time/chrono test/java/time/format

15. Create a patch
 Let’s contribute
cd $SOURCE_CODE/jdk9
 Commit in Mercurial
hg status
hg commit
 Run webrev
ksh ../webrev.ksh
 Upload to web server
$SOURCE_CODE/jdk9/webrev