Package com.ibm.icu.text

Class MessagePattern

  • All Implemented Interfaces:
    Freezable<MessagePattern>, Cloneable
    public final class MessagePattern
extends Object
implements Cloneable, Freezable<MessagePattern>
    Parses and represents ICU MessageFormat patterns. Also handles patterns for ChoiceFormat, PluralFormat and SelectFormat. Used in the implementations of those classes as well as in tools for message validation, translation and format conversion.

    The parser handles all syntax relevant for identifying message arguments. This includes "complex" arguments whose style strings contain nested MessageFormat pattern substrings. For "simple" arguments (with no nested MessageFormat pattern substrings), the argument style is not parsed any further.

    The parser handles named and numbered message arguments and allows both in one message.

    Once a pattern has been parsed successfully, iterate through the parsed data with countParts(), getPart() and related methods.

    The data logically represents a parse tree, but is stored and accessed as a list of "parts" for fast and simple parsing and to minimize object allocations. Arguments and nested messages are best handled via recursion. For every _START "part", getLimitPartIndex(int) efficiently returns the index of the corresponding _LIMIT "part".

    List of "parts": 

     message = MSG_START (SKIP_SYNTAX | INSERT_CHAR | REPLACE_NUMBER | argument)* MSG_LIMIT
 argument = noneArg | simpleArg | complexArg
 complexArg = choiceArg | pluralArg | selectArg

 noneArg = ARG_START.NONE (ARG_NAME | ARG_NUMBER) ARG_LIMIT.NONE
 simpleArg = ARG_START.SIMPLE (ARG_NAME | ARG_NUMBER) ARG_TYPE [ARG_STYLE] ARG_LIMIT.SIMPLE
 choiceArg = ARG_START.CHOICE (ARG_NAME | ARG_NUMBER) choiceStyle ARG_LIMIT.CHOICE
 pluralArg = ARG_START.PLURAL (ARG_NAME | ARG_NUMBER) pluralStyle ARG_LIMIT.PLURAL
 selectArg = ARG_START.SELECT (ARG_NAME | ARG_NUMBER) selectStyle ARG_LIMIT.SELECT

 choiceStyle = ((ARG_INT | ARG_DOUBLE) ARG_SELECTOR message)+
 pluralStyle = [ARG_INT | ARG_DOUBLE] (ARG_SELECTOR [ARG_INT | ARG_DOUBLE] message)+
 selectStyle = (ARG_SELECTOR message)+
    • Literal output text is not represented directly by "parts" but accessed between parts of a message, from one part's getLimit() to the next part's getIndex().
    • ARG_START.CHOICE stands for an ARG_START Part with ArgType CHOICE.
    • In the choiceStyle, the ARG_SELECTOR has the '<', the '#' or the less-than-or-equal-to sign (U+2264).
    • In the pluralStyle, the first, optional numeric Part has the "offset:" value. The optional numeric Part between each (ARG_SELECTOR, message) pair is the value of an explicit-number selector like "=2", otherwise the selector is a non-numeric identifier.
    • The REPLACE_NUMBER Part can occur only in an immediate sub-message of the pluralStyle.

      This class is not intended for public subclassing.

    • Constructor Detail

      • MessagePattern

        public MessagePattern()
        Constructs an empty MessagePattern with default ApostropheMode.

      • MessagePattern

        public MessagePattern​(MessagePattern.ApostropheMode mode)
        Constructs an empty MessagePattern.
        Parameters:
        mode - Explicit ApostropheMode.

      • MessagePattern

        public MessagePattern​(String pattern)
        Constructs a MessagePattern with default ApostropheMode and parses the MessageFormat pattern string.
        Parameters:
        pattern - a MessageFormat pattern string
        Throws:
        IllegalArgumentException - for syntax errors in the pattern string
        IndexOutOfBoundsException - if certain limits are exceeded (e.g., argument number too high, argument name too long, etc.)
        NumberFormatException - if a number could not be parsed

    • Method Detail

      • clear

        public void clear()
        Clears this MessagePattern. countParts() will return 0.

      • clearPatternAndSetApostropheMode

        public void clearPatternAndSetApostropheMode​(MessagePattern.ApostropheMode mode)
        Clears this MessagePattern and sets the ApostropheMode. countParts() will return 0.
        Parameters:
        mode - The new ApostropheMode.

      • equals

        public boolean equals​(Object other)
        Description copied from class: Object
        Compares this instance with the specified object and indicates if they are equal. In order to be equal, o must represent the same object as this instance using a class-specific comparison. The general contract is that this comparison should be reflexive, symmetric, and transitive. Also, no object reference other than null is equal to null.

        The default implementation returns true only if this == o. See Writing a correct equals method if you intend implementing your own equals method.

        The general contract for the equals and Object.hashCode() methods is that if equals returns true for any two objects, then hashCode() must return the same value for these objects. This means that subclasses of Object usually override either both methods or neither of them.

        Overrides:
        equals in class Object
        Parameters:
        other - another object to compare with.
        Returns:
        true if this object is equivalent to the other one.
        See Also:
        Object.hashCode()

      • hashCode

        public int hashCode()
        Returns an integer hash code for this object. By contract, any two objects for which Object.equals(java.lang.Object) returns true must return the same hash code value. This means that subclasses of Object usually override both methods or neither method.

        Note that hash values must not change over time unless information used in equals comparisons also changes.

        See Writing a correct hashCode method if you intend implementing your own hashCode method.

        Overrides:
        hashCode in class Object
        Returns:
        this object's hash code.
        See Also:
        Object.equals(java.lang.Object)

      • getPatternString

        public String getPatternString()
        Returns:
        the parsed pattern string (null if none was parsed).

      • hasNamedArguments

        public boolean hasNamedArguments()
        Does the parsed pattern have named arguments like {first_name}?
        Returns:
        true if the parsed pattern has at least one named argument.

      • hasNumberedArguments

        public boolean hasNumberedArguments()
        Does the parsed pattern have numbered arguments like {2}?
        Returns:
        true if the parsed pattern has at least one numbered argument.

      • toString

        public String toString()
        Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression: 
           getClass().getName() + '@' + Integer.toHexString(hashCode())

        See Writing a useful toString method if you intend implementing your own toString method.

        Overrides:
        toString in class Object
        Returns:
        a printable representation of this object.

      • validateArgumentName

        public static int validateArgumentName​(String name)
        Validates and parses an argument name or argument number string. An argument name must be a "pattern identifier", that is, it must contain no Unicode Pattern_Syntax or Pattern_White_Space characters. If it only contains ASCII digits, then it must be a small integer with no leading zero.
        Parameters:
        name - Input string.
        Returns:
        >=0 if the name is a valid number, ARG_NAME_NOT_NUMBER (-1) if it is a "pattern identifier" but not all ASCII digits, ARG_NAME_NOT_VALID (-2) if it is neither.

      • autoQuoteApostropheDeep

        public String autoQuoteApostropheDeep()
        Returns a version of the parsed pattern string where each ASCII apostrophe is doubled (escaped) if it is not already, and if it is not interpreted as quoting syntax.

        For example, this turns "I don't '{know}' {gender,select,female{h''er}other{h'im}}." into "I don''t '{know}' {gender,select,female{h''er}other{h''im}}."

        Returns:
        the deep-auto-quoted version of the parsed pattern string.
        See Also:
        MessageFormat.autoQuoteApostrophe(String)

      • countParts

        public int countParts()
        Returns the number of "parts" created by parsing the pattern string. Returns 0 if no pattern has been parsed or clear() was called.
        Returns:
        the number of pattern parts.

      • getPart

        public MessagePattern.Part getPart​(int i)
        Gets the i-th pattern "part".
        Parameters:
        i - The index of the Part data. (0..countParts()-1)
        Returns:
        the i-th pattern "part".
        Throws:
        IndexOutOfBoundsException - if i is outside the (0..countParts()-1) range

      • getPartType

        public MessagePattern.Part.Type getPartType​(int i)
        Returns the Part.Type of the i-th pattern "part". Convenience method for getPart(i).getType().
        Parameters:
        i - The index of the Part data. (0..countParts()-1)
        Returns:
        The Part.Type of the i-th Part.
        Throws:
        IndexOutOfBoundsException - if i is outside the (0..countParts()-1) range

      • getPatternIndex

        public int getPatternIndex​(int partIndex)
        Returns the pattern index of the specified pattern "part". Convenience method for getPart(partIndex).getIndex().
        Parameters:
        partIndex - The index of the Part data. (0..countParts()-1)
        Returns:
        The pattern index of this Part.
        Throws:
        IndexOutOfBoundsException - if partIndex is outside the (0..countParts()-1) range

      • getSubstring

        public String getSubstring​(MessagePattern.Part part)
        Returns the substring of the pattern string indicated by the Part. Convenience method for getPatternString().substring(part.getIndex(), part.getLimit()).
        Parameters:
        part - a part of this MessagePattern.
        Returns:
        the substring associated with part.

      • partSubstringMatches

        public boolean partSubstringMatches​(MessagePattern.Part part,
                                    String s)
        Compares the part's substring with the input string s.
        Parameters:
        part - a part of this MessagePattern.
        s - a string.
        Returns:
        true if getSubstring(part).equals(s).

      • getNumericValue

        public double getNumericValue​(MessagePattern.Part part)
        Returns the numeric value associated with an ARG_INT or ARG_DOUBLE.
        Parameters:
        part - a part of this MessagePattern.
        Returns:
        the part's numeric value, or NO_NUMERIC_VALUE if this is not a numeric part.

      • getPluralOffset

        public double getPluralOffset​(int pluralStart)
        Returns the "offset:" value of a PluralFormat argument, or 0 if none is specified.
        Parameters:
        pluralStart - the index of the first PluralFormat argument style part. (0..countParts()-1)
        Returns:
        the "offset:" value.
        Throws:
        IndexOutOfBoundsException - if pluralStart is outside the (0..countParts()-1) range

      • getLimitPartIndex

        public int getLimitPartIndex​(int start)
        Returns the index of the ARG|MSG_LIMIT part corresponding to the ARG|MSG_START at start.
        Parameters:
        start - The index of some Part data (0..countParts()-1); this Part should be of Type ARG_START or MSG_START.
        Returns:
        The first i>start where getPart(i).getType()==ARG|MSG_LIMIT at the same nesting level, or start itself if getPartType(msgStart)!=ARG|MSG_START.
        Throws:
        IndexOutOfBoundsException - if start is outside the (0..countParts()-1) range

      • clone

        public Object clone()
        Creates and returns a copy of this object.
        Overrides:
        clone in class Object
        Returns:
        a copy of this object (or itself if frozen).

      • isFrozen

        public boolean isFrozen()
        Determines whether this object is frozen (immutable) or not.
        Specified by:
        isFrozen in interface Freezable<MessagePattern>
        Returns:
        true if this object is frozen.