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All of the hashing based Map implementations: HashMap, Hashtable, LinkedHashMap, WeakHashMap and ConcurrentHashMap are modified to use an enhanced hashing algorithm for string keys when the capacity of the hash table has ever grown beyond 512 entries. The enhanced hashing implementation uses the murmur3 hashing algorithm along with random hash seeds and index masks. These enhancements mitigate cases where colliding String hash values could result in a performance bottleneck. Reviewed-by: alanb, forax, dl
README:
This file should be located at the top of the OpenJDK Mercurial root
repository. This root repository will include a "make" directory,
and a Makefile for building the entire OpenJDK.
A full OpenJDK repository set (forest) should also include the following
6 nested repositories:
"jdk", "hotspot", "langtools", "corba", "jaxws" and "jaxp".
There are also several source downloads for the jax* repositories that
will be needed.
This one root repository can be obtained with something like:
hg clone http://hg.openjdk.java.net/jdk8/jdk8 openjdk8
To make sure you have all the nested repositories, you can run the
get_source.sh script located in the same respository as this file:
cd openjdk8 && sh ./get_source.sh
People unfamiliar with Mercurial should read the first few chapters of
the Mercurial book: http://hgbook.red-bean.com/read/
See http://openjdk.java.net/ for more information about the OpenJDK.
Simple Build Instructions:
0. Get the necessary system software/packages installed on your system, see
http://hg.openjdk.java.net/jdk8/build/raw-file/tip/README-builds.html
1. If you don't have a jdk6 installed, download and install a JDK 6 from
http://java.sun.com/javase/downloads/index.jsp
Set the environment variable ALT_BOOTDIR to the location of JDK 6.
2. Check the sanity of doing a build with your current system:
make sanity
See README-builds.html if you run into problems.
3. Do a complete build of the OpenJDK:
make all
The resulting JDK image should be found in build/*/j2sdk-image
where make is GNU make 3.81 or newer, /usr/bin/make on Linux usually
is 3.81 or newer.
Complete details are available in README-builds.html.
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