This document summarizes how to build and extend the OpenJDK reference implementation of Java. It outlines downloading the source code from Mercurial repositories, building the code using a simple make command, and extending it by following examples. It also introduces Jtreg for testing code and provides URLs for the Shenandoah garbage collector and Java 9 development codebases.

1. Michał Warecki
OpenJDK Hackathon
Building and extending OpenJDK

2. Outline
● Introduction to OpenJDK
● Building OpenJDK
● Extending OpenJDK
● Introduction to Jtreg
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3. OpenJDK
● Reference implementation of JLS and JVM
● Open source
● Tools (JVisualVM, JMH, jHAT etc.)
● Extensions (e. g. Nashorn)
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4. OpenJDK
[michal@michal openjdk8]$ tree -L 1 -d
├── build
├── common
├── corba
├── hotspot
├── jaxp
├── jaxws
├── jdk
├── langtools
├── make
├── nashorn
└── test
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5. Download the code!
$ hg clone http://hg.openjdk.java.net/jdk8/jdk8 openjdk8
$ cd openjdk8
$ chmod a+x get_source.sh
$ ./get_source.sh
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6. Alternatives (try it!)
● Brand new Shenandoah GC:
$ hg clone http://icedtea.classpath.org/hg/shenandoah/openjdk8
shenandoah
● Java 9:
$ hg clone http://hg.openjdk.java.net/jdk9/dev 9dev

7. Look at the code!
10 minutes
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8. Build the code!
$ chmod a+x configure
$ bash configure
$ make clean images
(yes, that's it, simple)
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9. Extend OpenJDK
Follow the leading
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10. Run the test!
https://github.com/michalwarecki/OpenJDKHackaton.git
$ ./run_test.sh $DIR_OR_TEST_TO_RUN
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11. Look at the test code!
Follow the leading
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12. Make your own extension!
20 minutes
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13. Thanks!