International Components for Unicode for Java (ICU4J)

Read Me for ICU4J 4.4

Release Date
March 17, 2010

Note: This is major release of ICU4J. It contains bug fixes and adds implementations of inherited API and introduces new API or functionality.

For the most recent release, see the ICU4J download site.

Contents

• Introduction to ICU4J
• Changes In This Release
• License Information
• Platform Dependencies
• How to Download ICU4J
• The Structure and Contents of ICU4J
• Where to Get Documentation
• How to Install and Build
• How to modularize ICU4J
• Trying Out ICU4J
• ICU4J Resource Information
• About ICU4J Time Zone
• Where to Find More Information
• Submitting Comments, Requesting Features and Reporting Bugs

Introduction to ICU4J

The International Components for Unicode (ICU) library provides robust and full-featured Unicode services on a wide variety of platforms. ICU supports the most current version of the Unicode standard, including support for supplementary characters (needed for GB 18030 repertoire support).

Java provides a strong foundation for global programs, and IBM and the ICU team played a key role in providing globalization technology to Java. But because of its long release schedule, Java cannot always keep up with evolving standards. The ICU team continues to extend Java's Unicode and internationalization support, focusing on improving performance, keeping current with the Unicode standard, and providing richer APIs, while remaining as compatible as possible with the original Java text and internationalization API design.

ICU4J is an add-on to the regular JRE that provides:

• Collation – rule-based, up-to-date Unicode Collation Algorithm (UCA) sorting order
      For fast multilingual string comparison; faster and more complete than the J2SE implementation
• Supplementary Characters – String manipulation and character properties
      Required for proper GB 18030 and JIS X 0213 repertoire support
• Charset Detection – Recognition of various single and multibyte charsets
      Useful for recognizing untagged text data
• UnicodeSet – standard set operations optimized for sets of Unicode characters
      UnicodeSets can be built from string patterns using any Unicode properties.
• Transforms – a flexible mechanism for Unicode text conversions
      Including Full/Halfwidth conversions, Normalization, Case conversions, Hex conversions, and transliterations between scripts (50+ pairs)
• Unicode Normalization – NFC, NFD, NFKD, NFKC
      For canonical text representations, needed for XML and the net
• International Calendars – Arabic, Buddhist, Chinese, Hebrew, Japanese, Ethiopic, Islamic, Coptic and other calendars
      Required for correct presentation of dates in certain countries
• Number Format Enhancements – Scientific Notation, Spelled-out, etc.
      Enhancements to the normal Java number formatting. The spell-out format is used for checks and similar documents
• Enhanced Word-Break Detection – Rule-based, supports Thai
      Required for correct support of Thai
• Unicode Text Compression – Standard compression of Unicode text
      Suitable for large numbers of small fields, where LZW and similar schemes do not apply
• Charset Conversion – Conversion to and from different charsets.
      Plugs into Java CharsetProvider Service Provider Interface (SPI)

Note: We continue to provide assistance to Sun, and in some cases, ICU4J support has been rolled into a later release of Java. For example, the Thai word-break is now in Java 1.4. However, the most current and complete version is always found in ICU4J.

Changes In This Release

Minimum Java runtime environment requirement

Starting with version 4.4, you need at least JRE 5.0 to use ICU4J 4.4. ICU4J adopted Java 5 language features and no longer compiles with JDK 1.4 or older versions. This migration also includes some updates in public API signatures, such as generics and return/parameter types. In general, most of these changes do not require any changes in existing ICU4J user code.

TimeZone serialization compatibility

The new system time zone data format supporting 64bit transition time data implemented in ICU4J 4.4 introduced a serialization incompatibility issue in the internal TimeZone implementation class (e.g. An instance of TimeZone created by TimeZone.getTimeZone(String) with an Olson tzid, such as "America/Los_Angeles"). The new implementation reads only the system time zone identifier string when object data was serialized by ICU4J 4.2 or older versions. Also, ICU4J 4.2 or older versions cannot read object data created by ICU4J 4.4. The system time zone implementation class may be used by other ICU4J public API classes, such as Calendar and DateFormat, therefore, these classes are also affected.

For the ICU4J serialization compatibility policy, please refer the user guide section ICU4J Serialization Compatibility.

New features and other changes

See the ICU 4.4 download page about new features in this release. The list of API changes since the previous ICU4J release is available here.

License Information

The ICU projects (ICU4C and ICU4J) use the X license. The X license is suitable for commercial use and is a recommended free software license that is compatible with the GNU GPL license. This became effective with release 1.8.1 of ICU4C and release 1.3.1 of ICU4J in mid-2001. All new ICU releases will adopt the X license; previous ICU releases continue to utilize the IPL (IBM Public License). Users of previous releases of ICU who want to adopt new ICU releases will need to accept the terms and conditions of the X license.

The main effect of the change is to provide GPL compatibility. The X license is listed as GPL compatible, see the GNU page at http://www.gnu.org/philosophy/license-list.html#GPLCompatibleLicenses. This means that GPL projects can now use ICU code, it does not mean that projects using ICU become subject to GPL.

The IBM version contains the essential text of the license, omitting the X-specific trademarks and copyright notices. The full copy of ICU's license is included in the download package.

Platform Dependencies

ICU4J 4.4 depends on J2SE 5.0 functionality. Therefore, ICU4J only runs on JRE version 5.0 or later. The table below shows the operating systems and JRE/VM versions currently used by the ICU development team to test ICU4J.

How to Download ICU4J

There are two ways to download the ICU4J releases.

• Official Release:
  If you want to use ICU4J (as opposed to developing it), your best bet is to download an official, packaged version of the ICU4J library files. These versions are tested more thoroughly than day-to-day development builds, and they are packaged in jar files for convenient download. These packaged files can be found at the ICU Download page.

• Subversion Source Repository:
  If you are interested in developing features, patches, or bug fixes for ICU4J, you should probably be working with the latest version of the ICU4J source code. You will need to check the code out of our Subversion repository to ensure that you have the most recent version of all of the files. There are several ways to do this. Please follow the directions that are contained on the Source Repository page for details.

For more details on how to download ICU4J directly from the web site, please see the ICU download page at http://www.icu-project.org/download/

The Structure and Contents of ICU4J

Below, all directory pathes are relative to the directory where the ICU4J source archive is extracted.

Information and build files:

ICU4J runtime class files:

ICU4J unit test files:

Others:

Where to get Documentation

The ICU user's guide contains lots of general information about ICU, in its C, C++, and Java incarnations.

The complete API documentation for ICU4J (javadoc) is available on the ICU4J web site, and can be built from the sources:

• Index to all ICU4J API
• Charset Detector – Detection of charset from a byte stream
• International Calendars – Buddhist, Chinese, Coptic, Ethiopic, Gregorian, Hebrew, Indian, Islamic, Japanese.
• Unicode Normalization – Canonical text representation for W3C.
• Number Format Enhancements – Scientific Notation, Spelled out.
• Enhanced word-break detection – Rule-based, supports Thai
• Transliteration – A general framework for converting text from one format to another, e.g. Cyrillic to Latin, or Hex to Unicode.
• Unicode Text Compression & Decompression – 2:1 compression on English Unicode text.
• Collation - Rule-based sorting, Efficient multi-lingual searching

How to Install and Build

To install ICU4J, simply place the prebuilt jar file icu4j.jar on your Java CLASSPATH. If you need Charset API support please also place icu4j-charsets.jar on your class path along with icu4j.jar.

To build ICU4J, you will need J2SE SDK 5.0 or later (ICU4J locale SPI provider sub-components require J2SE SDK 6.0 or later) and the Ant build system version 1.7 or later. It's recommended to install both the J2SE SDK and Ant somewhere outsidethe ICU4J directory. For example, on Linux you might install these in /usr/local.

• Install J2SE SDK 6.0.
• Install the Ant build system. Ant is a portable, Java-based build system similar to make. ICU4J uses Ant because it introduces no other dependencies, it's portable, and it's easier to manage than a collection of makefiles. We currently build ICU4J using a single makefile on all platforms Ant. The build system requires Ant 1.7 or later.

  Installing Ant is straightforward. Download it (see http://ant.apache.org/bindownload.cgi), extract it onto your system, set some environment variables, and add its bin directory to your path. For example:

          set JAVA_HOME=C:\jdk1.6.0
          set ANT_HOME=C:\ant
          set PATH=%PATH%;%ANT_HOME%\bin

  See the current Ant documentation for details.

Once the J2SE SDK and Ant are installed, building is just a matter of typing ant in the ICU4J root directory. This causes the Ant build system to perform the build target jar as specified by the file build.xml, located in the ICU4J root directory. You can give Ant options like -verbose, and you can specify other targets. For example:

C:\icu4j>ant
Buildfile: build.xml

info:
     [echo] ----- Build Environment Information -------------------
     [echo] Java Home:    C:\jdk1.6.0
     [echo] Java Version: 1.6.0
     [echo] Ant Home:     C:\ant
     [echo] Ant Version:  Apache Ant version 1.7.1 compiled on June 27 2008
     [echo] OS:           Windows Vista
     [echo] OS Version:   6.1 build 7600
     [echo] OS Arch:      x86
     [echo] Host:         ICUDEV
     [echo] -------------------------------------------------------

core:

@compile:
     [echo] --- java compiler arguments ------------------------
     [echo] source dir:     C:\icu4j\main\classes\core/src
     [echo] output dir:     C:\icu4j\main\classes\core/out/bin
     [echo] classpath:
     [echo] source:         1.5
     [echo] target:         1.5
     [echo] debug:          on
     [echo] encoding:       ascii
     [echo] compiler arg:   -Xlint:all,-deprecation,-dep-ann
     [echo] ----------------------------------------------------
    [mkdir] Created dir: C:\icu4j\main\classes\core\out\bin
    [javac] Compiling 316 source files to C:\icu4j\main\classes\core\out\bin
    [javac] Note: Some input files use or override a deprecated API.
    [javac] Note: Recompile with -Xlint:deprecation for details.

compile:

@copy:
     [copy] Copying 23 files to C:\icu4j\main\classes\core\out\bin

copy-data:
    [unjar] Expanding: C:\icu4j\main\shared\data\icudata.jar into C:\icu4j\main\classes\core\out\bin

....
....
....

build:

_build-localespi:

@compile:
     [echo] --- java compiler arguments ------------------------
     [echo] source dir:     C:\icu4j\main\classes\localespi/src
     [echo] output dir:     C:\icu4j\main\classes\localespi/out/bin
     [echo] classpath:      C:\icu4j\main\classes\core\out\lib\icu4j-core.jar;C:\icu4j\main\classes\collate\
out\lib\icu4j-collate.jar
     [echo] source:         1.6
     [echo] target:         1.6
     [echo] debug:          on
     [echo] encoding:       ascii
     [echo] compiler arg:   -Xlint:all,-deprecation,-dep-ann
     [echo] ----------------------------------------------------
    [mkdir] Created dir: C:\icu4j\main\classes\localespi\out\bin
    [javac] Compiling 22 source files to C:\icu4j\main\classes\localespi\out\bin

compile:

@copy:
     [copy] Copying 10 files to C:\icu4j\main\classes\localespi\out\bin

copy:

@jar:
    [mkdir] Created dir: C:\icu4j\main\classes\localespi\out\lib
     [copy] Copying 1 file to C:\icu4j\main\classes\localespi\out
      [jar] Building jar: C:\icu4j\main\classes\localespi\out\lib\icu4j-localespi.jar

jar:

build:

jar:
     [copy] Copying 1 file to C:\icu4j
     [copy] Copying 1 file to C:\icu4j

BUILD SUCCESSFUL
Total time: 24 seconds

The following are some targets that you can provide to ant. For more targets run ant -projecthelp or see the build.xml file.

For more information, read the Ant documentation and the build.xml file.

Eclipse users: See the ICU4J site for information on how to configure Eclipse to build and develop ICU4J on Eclipse IDE.

Note: To install ICU4J Locale Service Provider, please refer Read Me for ICU4J Locale Service Provider.

How to modularize ICU4J

Some clients may not wish to ship all of ICU4J with their application, since the application might only use a small part of ICU4J. ICU4J release 2.6 and later provide build options to build individual ICU4J 'modules' for a more compact distribution. For more details, please refer to the section Modularization of ICU4J in the ICU user's guide article Packaging ICU4J.

Trying Out ICU4J

Note: the demos provided with ICU4J are for the most part undocumented. This list can show you where to look, but you'll have to experiment a bit. The demos are unsupported and may change or disappear without notice.

The icu4j.jar file contains only the ICU4J runtime library classes, not the demo classes, so unless you build ICU4J there is little to try out.

Charset

java -cp $icu4j_root/icu4j.jar:$icu4j_root/icu4j-charsets.jar <your program>

Other demos

The other demo programs are not supported and exist only to let you experiment with the ICU4J classes. First, build ICU4J using ant jarDemos. Then launch the demos as below:

java -jar $icu4j_root/icu4jdemos.jar

ICU4J Resource Information

By default the ICU4J distribution includes all of the standard resource information. It is located under the directory com/ibm/icu/impl/data. Depending on the service, the data is in different locations and in different formats. Note: This will continue to change from release to release, so clients should not depend on the exact organization of the data in ICU4J.

• The primary locale data is under the directory icudt44b, as a set of ".res" files whose names are the locale identifiers. Locale naming is documented the com.ibm.icu.util.ULocale class, and the use of these names in searching for resources is documented in com.ibm.icu.util.UResourceBundle.
• The collation data is under the directory icudt44b/coll, as a set of ".res" files.
• The currency display name data is under the directory icudt44b/curr, as a set of ".res" files.
• The language display name data is under the directory icudt44b/lang, as a set of ".res" files.
• The region display name data is under the directory icudt44b/region, as a set of ".res" files.
• The rule-based transliterator data is under the directory icudt44b/translit, as a set of ".res" files.
• The rule-based number format data is under the directory icudt44b/rbnf, as a set of ".res" files.
• The break iterator data is directly under the directory icudt44b, as a set of ".brk" files, named according to the type of break and the locale where there are locale-specific versions.
• The holiday data is under the directory icudt44b, as a set of ".class" files, named "HolidayBundle_" followed by the locale ID.
• The character property data as well as assorted normalization data and default unicode collation algorithm (UCA) data is found under the directory icudt44b, as a set of ".icu" files.
• The character set converter data is under the directory icudt44b, as a set of ".cnv" files. These files are currently included only in icu-charset.jar.
• The time zone rule data is under the directory icudt44b, as zoneinfo64.res.
• The time zone display name data is under the directory icudt44b/zone, as a set of ".res" files.

Some of the data files alias or otherwise reference data from other data files. One reason for this is because some locale names have changed. For example, he_IL used to be iw_IL. In order to support both names but not duplicate the data, one of the resource files refers to the other file's data. In other cases, a file may alias a portion of another file's data in order to save space. Currently ICU4J provides no tool for revealing these dependencies.

Note: Java's Locale class silently converts the language code "he" to "iw" when you construct the Locale (for versions of Java through Java 5). Thus Java cannot be used to locate resources that use the "he" language code. ICU, on the other hand, does not perform this conversion in ULocale, and instead uses aliasing in the locale data to represent the same set of data under different locale ids.

Resource files that use locale ids form a hierarchy, with up to four levels: a root, language, region (country), and variant. Searches for locale data attempt to match as far down the hierarchy as possible, for example, "he_IL" will match he_IL, but "he_US" will match he (since there is no US variant for he, and "xx_YY will match root (the default fallback locale) since there is no xx language code in the locale hierarchy. Again, see java.util.ResourceBundle for more information.

Currently ICU4J provides no tool for revealing these dependencies between data files, so trimming the data directly in the ICU4J project is a hit-or-miss affair. The key point when you remove data is to make sure to remove all dependencies on that data as well. For example, if you remove he.res, you need to remove he_IL.res, since it is lower in the hierarchy, and you must remove iw.res, since it references he.res, and iw_IL.res, since it depends on it (and also references he_IL.res).

Unfortunately, the jar tool in the JDK provides no way to remove items from a jar file. Thus you have to extract the resources, remove the ones you don't want, and then create a new jar file with the remining resources. See the jar tool information for how to do this. Before 'rejaring' the files, be sure to thoroughly test your application with the remaining resources, making sure each required resource is present.

Using additional resource files with ICU4J

Warning: Resource file formats can change across releases of ICU4J!

The format of ICU4J resources is not part of the API. Clients who develop their own resources for use with ICU4J should be prepared to regenerate them when they move to new releases of ICU4J.

We are still developing ICU4J's resource mechanism. Currently it is not possible to mix icu's new binary .res resources with traditional java-style .class or .txt resources. We might allow for this in a future release, but since the resource data and format is not formally supported, you run the risk of incompatibilities with future releases of ICU4J.

Resource data in ICU4J is checked in to the repository as a jar file containing the resource binaries, icudata.jar. This means that inspecting the contents of these resources is difficult. They currently are compiled from ICU4C .txt file data. You can view the contents of the ICU4C text resource files to understand the contents of the ICU4J resources.

The files in icudata.jar get extracted to com/ibm/icu/impl/data in the build directory when the 'core' target is built. Building the 'resources' target will force the resources to once again be extracted. Extraction will overwrite any corresponding resource files already in that directory.

Building ICU4J Resources from ICU4C

Generating Data from CLDR

1. Checkout CLDR. $cldr_root in the following steps is the root directory where the CLDR source files checked out.
2. Update $cldr_root/common to 'release-1-8-0' tag
3. Update $cldr_root/tools to 'release-1-8-0' tag
4. Checkout ICU4C with tag 'release-4-4'
5. Checkout ICU4J with tag 'release-4-4'
6. Build ICU4J
7. Build ICU4C
8. Change to $cldr_root/tools/java directory
9. Build CLDR using ant after pointing ICU4J_CLASSES env var to the newly build ICU4J
10. cd to $icu4c_root/source/data directory
11. Follow the instructions in the cldr-icu-readme.txt
12. Build ICU4C data from CLDR
13. Build ICU4J data from ICU4C data by following the procedures in $icu4c_root/source/data/icu4j-readme.txt
14. cd to $icu4j_root dir
15. Build and test icu4j

About ICU4J Time Zone

ICU4J 4.4 includes time zone data version 2010e, which is the latest one as of the release date. However, time zone data is frequently updated in response to changes made by local governments around the world. If you need to update the time zone data, please refer the ICU user guide topic Updating the Time Zone Data.

Starting with ICU4J 4.0, you can optionally configure ICU4J date and time service classes to use underlying JDK TimeZone implementation (see the ICU4J API reference TimeZone for the details). When this configuration is enabled, ICU's own time zone data won't be used and you have to get time zone data patches from the JRE vendor.

Where to Find More Information

http://www.icu-project.org/ is the home page of International Components for Unicode development project

http://www.ibm.com/software/globalization/icu/ is a pointer to general information about the International Components for Unicode hosted by IBM

http://www.ibm.com/software/globalization/ is a pointer to information on how to make applications global.

Submitting Comments, Requesting Features and Reporting Bugs

Your comments are important to making ICU4J successful. We are committed to investigate any bug reports or suggestions, and will use your feedback to help plan future releases.

To submit comments, request features and report bugs, please see ICU bug database information or contact us through the ICU Support mailing list. While we are not able to respond individually to each comment, we do review all comments.

Thank you for your interest in ICU4J!

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