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<h2>International Components for Unicode for Java (ICU4J)</h2>
-<h3>Read Me for ICU4J 50 (50.1)</h3>
-(Last Update: 2012-Nov-02)
+<h3>Read Me for ICU4J 51</h3>
+(Last Update: 2013-Feb-11)
<hr size="2" width="100%">
<p><b>Note:</b> This is major release of ICU4J. It contains bug fixes and adds implementations
<h3 class="doc"><a name="changes"></a>Changes In This Release</h3>
-<p>See the <a href="http://sites.google.com/site/icusite/download/50">ICU 50 download page</a>
+<p>See the <a href="http://sites.google.com/site/icusite/download/51">ICU 51 download page</a>
about new features in this release.
The list of API changes since the previous ICU4J release is available
<a href="http://source.icu-project.org/repos/icu/icu4j/tags/release-50-1/APIChangeReport.html">here</a>.</p>
-<h4><code>Collator.ReorderCodes.DEFAULT</code> value</h4>
-<p>We changed the numeric value of
- <code>static final Collator.ReorderCodes.DEFAULT</code> from +1 to -1
- so that it does not collide with a valid UScript code (<code>UScript.INHERITED</code>),
- and to make it match <code>UScript.INVALID_CODE</code> and C/C++ <code>UCOL_REORDER_CODE_DEFAULT</code>,
- as had been intended.
- Programs using <code>Collator.ReorderCodes.DEFAULT</code> must be recompiled.</p>
+<h4>Date format pattern "V"</h4>
+<p>The date format pattern "V" was introduced in ICU 3.8 (inherited from CLDR 1.5) as
+a variation of pattern "z" to support time zone abbreviation format such as "PST".
+The pattern "z" use a time zone abbreviation only when it is commonly used for a locale.
+The pattern "V" was slightly different from pattern "z" and the pattern designates
+a time zone abbreviation even it is not commonly used for a locale. For example, time
+zone abbreviation "AEST" for Australian Eastern Standard Time might not be well recognized
+by people in the United States. For the zone, pattern "z" does not use "AEST" (instead, use
+UTC offset format "GMT+10:00, as the fallback) , while pattern "V" used to print out "AEST".
+In CLDR 21, the data used for checking commonly used or not was completely removed (CLDR
+ticket <a href="http://unicode.org/cldr/trac/ticket/4052">#4052</a>), so the difference
+between pattern "z" and "V" is no longer available since ICU 49 (based on CLDR 21 specification).</p>
-<h4><code>class DictionaryBasedBreakIterator</code> has been removed.</h4>
+<p>In CLDR 23, the CLDR technical committee decided to reuse the semantically deprecated
+pattern "V" for a different purpose. With the new specification, the date format pattern
+"V" is used for short time zone IDs, such as "uslax" for zone America/Los_Angeles. ICU 51
+implements the new specification. So existing ICU users currently using custom date format
+patterns with pattern "V" are suggested to change them to pattern "z".</p>
-<p>The functionality of the <code>DictionaryBasedBreakIterator</code>
-was moved into the base <code>RuleBasedBreakIterator</code>, and improved.
-In particular, Java RBBI now handles multiple built-in dictionaries,
-selecting them by character script, as in C++.
-As a result, creating a BreakIterator for a particular language or dictionary is
-unnecessary and obsolete.</p>
+<p>Note that the existing pattern "VVVV" for a time zone's generic location name is not
+affected by the new specification and the pattern "VVVV" continues to work as same as
+previous ICU releases.</p>
-<p>The dictionary data structure was changed, so ICU 50 would not be able to
-handle an old <code>InputStream dictionaryStream</code>.
-(If we wanted to formally keep a <code>class DictionaryBasedBreakIterator</code>
-it would be an empty class, and its one public constructor would
-throw an <code>UnsupportedOperationException</code>.)</p>
-
-<p>The DBBI class was not usable by itself:
-A dictionary alone is not sufficient for dictionary-based breaking.
-For each dictionary there must be specific code with the specific matching algorithm
-(e.g., longest match vs. word-frequency-based word sequence probability)
-and with a script-specific test for whether a dictionary word was found at a syllable boundary
-(or whatever is the appropriate criterium).</p>
-
-<p>RBBI and its DBBI subclasses had an "intimate connection" and were not effectively separable.</p>
-
-<p>In C++, DBBI was already not public API and has been removed several years ago.</p>
-
-<p>If any users have subclasses of <code>class DictionaryBasedBreakIterator</code>,
-they will need to be changed to subclass <code>RuleBasedBreakIterator</code> directly.</p>
<h3 class="doc"><a name="license"></a>License Information</h3>
<p>
<h2>Thank you for your interest in ICU4J!</h2>
<br>
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-<p><I><font size="-1">Copyright © 2002-2012 International Business
+<p><I><font size="-1">Copyright © 2002-2013 International Business
Machines Corporation and others. All Rights
Reserved.<br>
4400 North First Street, San José, CA 95193, USA
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