Introductory slides on what is OpenJDK and why and how we should contribute to it. Given to the Bulgarian JUG before the first real adopt OpenJDK hackathon

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