Added in API level 24

SymbolTable

public interface SymbolTable

android.icu.text.SymbolTable

An interface that defines both lookup protocol and parsing of symbolic names.

This interface is used by UnicodeSet to resolve $Variable style references that appear in set patterns. RBBI and Transliteration both independently implement this interface.

A symbol table maintains two kinds of mappings. The first is between symbolic names and their values. For example, if the variable with the name "start" is set to the value "alpha" (perhaps, though not necessarily, through an expression such as "$start=alpha"), then the call lookup("start") will return the char[] array ['a', 'l', 'p', 'h', 'a'].

The second kind of mapping is between character values and UnicodeMatcher objects. This is used by RuleBasedTransliterator, which uses characters in the private use area to represent objects such as UnicodeSets. If U+E015 is mapped to the UnicodeSet [a-z], then lookupMatcher(0xE015) will return the UnicodeSet [a-z].

Finally, a symbol table defines parsing behavior for symbolic names. All symbolic names start with the SYMBOL_REF character. When a parser encounters this character, it calls parseReference() with the position immediately following the SYMBOL_REF. The symbol table parses the name, if there is one, and returns it.

Summary

Constants

char SYMBOL_REF

The character preceding a symbol reference name.

Public methods

abstract char[] lookup(String s)

Lookup the characters associated with this string and return it.

abstract UnicodeMatcher lookupMatcher(int ch)

Lookup the UnicodeMatcher associated with the given character, and return it.

abstract String parseReference(String text, ParsePosition pos, int limit)

Parse a symbol reference name from the given string, starting at the given position.

Constants

SYMBOL_REF

Added in API level 24 
public static final char SYMBOL_REF

The character preceding a symbol reference name.

Constant Value: 36 (0x00000024)

Public methods

lookup

Added in API level 24 
public abstract char[] lookup (String s)

Lookup the characters associated with this string and return it. Return null if no such name exists. The resultant array may have length zero.

Parameters
s String: the symbolic name to lookup
Returns
char[] a char array containing the name's value, or null if there is no mapping for s.

lookupMatcher

Added in API level 24 
public abstract UnicodeMatcher lookupMatcher (int ch)

Lookup the UnicodeMatcher associated with the given character, and return it. Return null if not found.

Parameters
ch int: a 32-bit code point from 0 to 0x10FFFF inclusive.
Returns
UnicodeMatcher the UnicodeMatcher object represented by the given character, or null if there is no mapping for ch.

parseReference

Added in API level 24 
public abstract String parseReference (String text, 
                ParsePosition pos, 
                int limit)

Parse a symbol reference name from the given string, starting at the given position. If no valid symbol reference name is found, return null and leave pos unchanged. That is, if the character at pos cannot start a name, or if pos is at or after text.length(), then return null. This indicates an isolated SYMBOL_REF character.

Parameters
text String: the text to parse for the name
pos ParsePosition: on entry, the index of the first character to parse. This is the character following the SYMBOL_REF character. On exit, the index after the last parsed character. If the parse failed, pos is unchanged on exit.
limit int: the index after the last character to be parsed.
Returns
String the parsed name, or null if there is no valid symbolic name at the given position.