Namespace List
Here is a list of all documented namespaces with brief descriptions:

icu | File coll.h
NoUnit | Dimensionless unit for percent and permille
AlphabeticIndex | AlphabeticIndex supports the creation of a UI index appropriate for a given language
Bucket | An index "bucket" with a label string and type
ImmutableIndex | Immutable, thread-safe version of AlphabeticIndex
AnnualTimeZoneRule | `AnnualTimeZoneRule` is a class used for representing a time zone rule which takes effect annually
Appendable | Base class for objects to which Unicode characters and strings can be appended
BasicTimeZone | `BasicTimeZone` is an abstract class extending `TimeZone`
BreakIterator | Implements methods for finding the location of boundaries in text
ByteSink | A ByteSink can be filled with bytes
BytesTrie | Light-weight, non-const reader class for a BytesTrie
Iterator | Iterator for all of the (byte sequence, value) pairs in a BytesTrie
State | BytesTrie state object, for saving a trie's current state and resetting the trie back to this state later
BytesTrieBuilder | Builder class for BytesTrie
Calendar | `Calendar` is an abstract base class for converting between a `UDate` object and a set of integer fields such as `YEAR`, `MONTH`, `DAY`, `HOUR`, and so on
CanonicalIterator | This class allows one to iterate through all the strings that are canonically equivalent to a given string
CaseMap | Low-level C++ case mapping functions
Char16Ptr | Char16_t * wrapper with implicit conversion from distinct but bit-compatible pointer types
CharacterIterator | Abstract class that defines an API for iteration on text objects
CheckedArrayByteSink | Implementation of ByteSink that writes to a flat byte array, with bounds-checking: This sink will not write more than capacity bytes to outbuf
ChoiceFormat | ChoiceFormat converts between ranges of numeric values and strings for those ranges
CollationElementIterator | Used as an iterator to walk through each character of an international string
CollationKey | Collation keys are generated by the Collator class
Collator | The `Collator` class performs locale-sensitive string comparison
CollatorFactory | A factory, used with registerFactory, the creates multiple collators and provides display names for them
CompactDecimalFormat | IMPORTANT: New users are strongly encouraged to see if numberformatter.h fits their use case
ConstChar16Ptr | Const char16_t * wrapper with implicit conversion from distinct but bit-compatible pointer types
ConstrainedFieldPosition | Represents a span of a string containing a given field
CurrencyAmount | A currency together with a numeric amount, such as 200 USD
CurrencyPluralInfo | This class represents the information needed by DecimalFormat to format currency plural, such as "3.00 US dollars" or "1.00 US dollar"
CurrencyUnit | A unit of currency, such as USD (U.S
DateFormat | DateFormat is an abstract class for a family of classes that convert dates and times from their internal representations to textual form and back again in a language-independent manner
DateFormatSymbols | DateFormatSymbols is a public class for encapsulating localizable date-time formatting data – including timezone data
DateInterval | This class represents a date interval
DateIntervalFormat | DateIntervalFormat is a class for formatting and parsing date intervals in a language-independent manner
DateIntervalInfo | DateIntervalInfo is a public class for encapsulating localizable date time interval patterns
DateTimePatternGenerator | This class provides flexible generation of date format patterns, like "yy-MM-dd"
DateTimeRule | `DateTimeRule` is a class representing a time in a year by a rule specified by month, day of month, day of week and time in the day
DecimalFormat | IMPORTANT: New users are strongly encouraged to see if numberformatter.h fits their use case
DecimalFormatSymbols | This class represents the set of symbols needed by DecimalFormat to format numbers
DisplayOptions | Represents all the display options that are supported by CLDR such as grammatical case, noun class, ... etc
Builder | Responsible for building `DisplayOptions`
Edits | Records lengths of string edits but not replacement text
Iterator | Access to the list of edits
ErrorCode | Wrapper class for UErrorCode, with conversion operators for direct use in ICU C and C++ APIs
ExternalBreakEngine | Define an abstract interface for the host environment to provide a low level facility to break text for unicode text in script that the text boundary cannot be handled by upper level rule based logic, for example, for Chinese and Japanese word breaking, Thai, Khmer, Burmese, Lao and other Southeast Asian scripts
FieldPosition | `FieldPosition` is a simple class used by `Format` and its subclasses to identify fields in formatted output
FieldPositionIterator | FieldPositionIterator returns the field ids and their start/limit positions generated by a call to Format::format
FilteredBreakIteratorBuilder | The BreakIteratorFilter is used to modify the behavior of a BreakIterator by constructing a new BreakIterator which suppresses certain segment boundaries
FilteredNormalizer2 | Normalization filtered by a UnicodeSet
FontRuns | The `FontRuns` class associates pointers to `LEFontInstance` objects with runs of text
Format | Base class for all formats
Formattable | Formattable objects can be passed to the Format class or its subclasses for formatting
FormattedDateInterval | An immutable class containing the result of a date interval formatting operation
FormattedList | An immutable class containing the result of a list formatting operation
FormattedRelativeDateTime | An immutable class containing the result of a relative datetime formatting operation
FormattedValue | An abstract formatted value: a string with associated field attributes
ForwardCharacterIterator | Abstract class that defines an API for forward-only iteration on text objects
GenderInfo | GenderInfo computes the gender of a list as a whole given the gender of each element
GregorianCalendar | Concrete class which provides the standard calendar used by most of the world
IDNA | Abstract base class for IDNA processing
IDNAInfo | Output container for IDNA processing errors
InitialTimeZoneRule | `InitialTimeZoneRule` represents a time zone rule representing a time zone effective from the beginning and has no actual start times
ListFormatter | An immutable class for formatting a list, using data from CLDR (or supplied separately)
LocalArray | "Smart pointer" class, deletes objects via the C++ array delete[] operator
Locale | A `Locale` object represents a specific geographical, political, or cultural region
ConvertingIterator | A generic Locale iterator implementation over Locale input iterators
Iterator | A Locale iterator interface similar to a Java Iterator<Locale>
RangeIterator | A generic Locale iterator implementation over Locale input iterators
LocaleBuilder | `LocaleBuilder` is used to build instances of `Locale` from values configured by the setters
LocaleDisplayNames | Returns display names of Locales and components of Locales
LocaleMatcher | Immutable class that picks the best match between a user's desired locales and an application's supported locales
Builder | LocaleMatcher builder
Result | Data for the best-matching pair of a desired and a supported locale
LocaleRuns | The `LocaleRuns` class associates pointers to `Locale` objects with runs of text
LocalPointer | "Smart pointer" class, deletes objects via the standard C++ delete operator
LocalPointerBase | "Smart pointer" base class; do not use directly: use LocalPointer etc
Measure | An amount of a specified unit, consisting of a number and a Unit
MeasureFormat |
MeasureUnit | A unit such as length, mass, volume, currency, etc
MessageFormat |
MessagePattern | Parses and represents ICU MessageFormat patterns
Part | A message pattern "part", representing a pattern parsing event
Normalizer | Old Unicode normalization API
Normalizer2 | Unicode normalization functionality for standard Unicode normalization or for using custom mapping tables
NumberFormat |
NumberFormatFactory | A NumberFormatFactory is used to register new number formats
NumberingSystem | Defines numbering systems
ParagraphLayout | ParagraphLayout
Line | This class represents a single line of text in a `ParagraphLayout`
VisualRun | This object represents a single visual run in a line of text in a paragraph
ParsePosition | `ParsePosition` is a simple class used by `Format` and its subclasses to keep track of the current position during parsing
PluralFormat |
PluralRules | Defines rules for mapping non-negative numeric values onto a small set of keywords
RegexMatcher | Class RegexMatcher bundles together a regular expression pattern and input text to which the expression can be applied
RegexPattern | Class `RegexPattern` represents a compiled regular expression
Region | `Region` is the class representing a Unicode Region Code, also known as a Unicode Region Subtag, which is defined based upon the BCP 47 standard
RelativeDateTimeFormatter | Formats simple relative dates
Replaceable | `Replaceable` is an abstract base class representing a string of characters that supports the replacement of a range of itself with a new string of characters
ResourceBundle | A class representing a collection of resource information pertaining to a given locale
RuleBasedBreakIterator | A subclass of BreakIterator whose behavior is specified using a list of rules
RuleBasedCollator | Implementation of Collator, using data-driven tables
RuleBasedNumberFormat | Formats numbers according to a set of rules
RuleBasedTimeZone | BasicTimeZone subclass implemented in terms of InitialTimeZoneRule and TimeZoneRule instances
RunArray | The `RunArray` class is a base class for building classes which represent data that is associated with runs of text
ScientificNumberFormatter | A formatter that formats numbers in user-friendly scientific notation
SearchIterator | `SearchIterator` is an abstract base class that provides methods to search for a pattern within a text string
SelectFormat |
SimpleDateFormat | SimpleDateFormat is a concrete class for formatting and parsing dates in a language-independent manner
SimpleFormatter | Formats simple patterns like "{1} was born in {0}"
SimpleNumberFormatFactory | A NumberFormatFactory that supports a single locale
SimpleTimeZone | `SimpleTimeZone` is a concrete subclass of `TimeZone` that represents a time zone for use with a Gregorian calendar
StringByteSink | Implementation of ByteSink that writes to a "string"
StringCharacterIterator | A concrete subclass of CharacterIterator that iterates over the characters (code units or code points) in a UnicodeString
StringEnumeration | Base class for 'pure' C++ implementations of uenum api
StringPiece | A string-like object that points to a sized piece of memory
StringSearch | `StringSearch` is a `SearchIterator` that provides language-sensitive text searching based on the comparison rules defined in a `RuleBasedCollator` object
SymbolTable | An interface that defines both lookup protocol and parsing of symbolic names
TimeArrayTimeZoneRule | `TimeArrayTimeZoneRule` represents a time zone rule whose start times are defined by an array of milliseconds since the standard base time
TimeUnit | Measurement unit for time units
TimeUnitAmount | Express a duration as a time unit and number
TimeUnitFormat | Format or parse a TimeUnitAmount, using plural rules for the units where available
TimeZone | `TimeZone` represents a time zone offset, and also figures out daylight savings
TimeZoneFormat | `TimeZoneFormat` supports time zone display name formatting and parsing
TimeZoneNames | `TimeZoneNames` is an abstract class representing the time zone display name data model defined by UTS#35 Unicode Locale Data Markup Language (LDML)
MatchInfoCollection | `MatchInfoCollection` represents a collection of time zone name matches used by `TimeZoneNames#find`
TimeZoneRule | `TimeZoneRule` is a class representing a rule for time zone
TimeZoneTransition | `TimeZoneTransition` is a class representing a time zone transition
Transliterator | `Transliterator` is an abstract class that transliterates text from one format to another
Token | A context integer or pointer for a factory function, passed by value
UCharCharacterIterator | A concrete subclass of CharacterIterator that iterates over the characters (code units or code points) in a char16_t array
UCharsTrie | Light-weight, non-const reader class for a UCharsTrie
Iterator | Iterator for all of the (string, value) pairs in a UCharsTrie
State | UCharsTrie state object, for saving a trie's current state and resetting the trie back to this state later
UCharsTrieBuilder | Builder class for UCharsTrie
UMemory | UMemory is the common ICU base class
UnicodeFilter | `UnicodeFilter` defines a protocol for selecting a subset of the full range (U+0000 to U+10FFFF) of Unicode characters
UnicodeFunctor | `UnicodeFunctor` is an abstract base class for objects that perform match and/or replace operations on Unicode strings
UnicodeMatcher | `UnicodeMatcher` defines a protocol for objects that can match a range of characters in a Replaceable string
UnicodeReplacer | `UnicodeReplacer` defines a protocol for objects that replace a range of characters in a Replaceable string with output text
UnicodeSet | A mutable set of Unicode characters and multicharacter strings
UnicodeSetIterator | UnicodeSetIterator iterates over the contents of a UnicodeSet
UnicodeString | UnicodeString is a string class that stores Unicode characters directly and provides similar functionality as the Java String and StringBuffer/StringBuilder classes
UnicodeStringAppendable | An Appendable implementation which writes to a UnicodeString
UObject | UObject is the common ICU "boilerplate" class
ValueRuns | The `ValueRuns` class associates integer values with runs of text
VTimeZone | `VTimeZone` is a class implementing RFC2445 VTIMEZONE