public final Class UCharacter

The UCharacter class provides extensions to the java.lang.Character class. These extensions provide support for more Unicode properties. Each ICU release supports the latest version of Unicode available at that time.

For some time before Java 5 added support for supplementary Unicode code points, The ICU UCharacter class and many other ICU classes already supported them. Some UCharacter methods and constants were widened slightly differently than how the Character class methods and constants were widened later. In particular, Character#MAX_VALUE is still a char with the value U+FFFF, while the UCharacter#MAX_VALUE is an int with the value U+10FFFF.

Code points are represented in these API using ints. While it would be more convenient in Java to have a separate primitive datatype for them, ints suffice in the meantime.

To use this class please add the jar file name icu4j.jar to the class path, since it contains data files which supply the information used by this file.
E.g. In Windows
set CLASSPATH=%CLASSPATH%;$JAR_FILE_PATH/ucharacter.jar.
Otherwise, another method would be to copy the files uprops.dat and unames.icu from the icu4j source subdirectory $ICU4J_SRC/src/com.ibm.icu.impl.data to your class directory $ICU4J_CLASS/com.ibm.icu.impl.data.

Aside from the additions for UTF-16 support, and the updated Unicode properties, the main differences between UCharacter and Character are:

• UCharacter is not designed to be a char wrapper and does not have APIs to which involves management of that single char.
  These include:
  • char charValue(),
  • int compareTo(java.lang.Character, java.lang.Character), etc.
• UCharacter does not include Character APIs that are deprecated, nor does it include the Java-specific character information, such as boolean isJavaIdentifierPart(char ch).
• Character maps characters 'A' - 'Z' and 'a' - 'z' to the numeric values '10' - '35'. UCharacter also does this in digit and getNumericValue, to adhere to the java semantics of these methods. New methods unicodeDigit, and getUnicodeNumericValue do not treat the above code points as having numeric values. This is a semantic change from ICU4J 1.3.1.

Further detail on differences can be determined using the program com.ibm.icu.dev.test.lang.UCharacterCompare

In addition to Java compatibility functions, which calculate derived properties, this API provides low-level access to the Unicode Character Database.

Unicode assigns each code point (not just assigned character) values for many properties. Most of them are simple boolean flags, or constants from a small enumerated list. For some properties, values are strings or other relatively more complex types.

For more information see "About the Unicode Character Database" (http://www.unicode.org/ucd/) and the ICU User Guide chapter on Properties (https://unicode-org.github.io/icu/userguide/strings/properties).

There are also functions that provide easy migration from C/POSIX functions like isblank(). Their use is generally discouraged because the C/POSIX standards do not define their semantics beyond the ASCII range, which means that different implementations exhibit very different behavior. Instead, Unicode properties should be used directly.

There are also only a few, broad C/POSIX character classes, and they tend to be used for conflicting purposes. For example, the "isalpha()" class is sometimes used to determine word boundaries, while a more sophisticated approach would at least distinguish initial letters from continuation characters (the latter including combining marks). (In ICU, BreakIterator is the most sophisticated API for word boundaries.) Another example: There is no "istitle()" class for titlecase characters.

ICU 3.4 and later provides API access for all twelve C/POSIX character classes. ICU implements them according to the Standard Recommendations in Annex C: Compatibility Properties of UTS #18 Unicode Regular Expressions (http://www.unicode.org/reports/tr18/#Compatibility_Properties).

API access for C/POSIX character classes is as follows:

- alpha:     isUAlphabetic(c) or hasBinaryProperty(c, UProperty.ALPHABETIC)
- lower:     isULowercase(c) or hasBinaryProperty(c, UProperty.LOWERCASE)
- upper:     isUUppercase(c) or hasBinaryProperty(c, UProperty.UPPERCASE)
- punct:     ((1<<getType(c)) & ((1<<DASH_PUNCTUATION)|(1<<START_PUNCTUATION)|
              (1<<END_PUNCTUATION)|(1<<CONNECTOR_PUNCTUATION)|(1<<OTHER_PUNCTUATION)|
              (1<<INITIAL_PUNCTUATION)|(1<<FINAL_PUNCTUATION)))!=0
- digit:     isDigit(c) or getType(c)==DECIMAL_DIGIT_NUMBER
- xdigit:    hasBinaryProperty(c, UProperty.POSIX_XDIGIT)
- alnum:     hasBinaryProperty(c, UProperty.POSIX_ALNUM)
- space:     isUWhiteSpace(c) or hasBinaryProperty(c, UProperty.WHITE_SPACE)
- blank:     hasBinaryProperty(c, UProperty.POSIX_BLANK)
- cntrl:     getType(c)==CONTROL
- graph:     hasBinaryProperty(c, UProperty.POSIX_GRAPH)
- print:     hasBinaryProperty(c, UProperty.POSIX_PRINT)

The C/POSIX character classes are also available in UnicodeSet patterns, using patterns like [:graph:] or \p{graph}.