Package org.apache.lucene.analysis.ja

Class JapaneseNumberFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    public class JapaneseNumberFilter
extends TokenFilter
    A TokenFilter that normalizes Japanese numbers (kansūji) to regular Arabic decimal numbers in half-width characters.

    Japanese numbers are often written using a combination of kanji and Arabic numbers with various kinds punctuation. For example, ３．２千 means 3200. This filter does this kind of normalization and allows a search for 3200 to match ３．２千 in text, but can also be used to make range facets based on the normalized numbers and so on.

    Notice that this analyzer uses a token composition scheme and relies on punctuation tokens being found in the token stream. Please make sure your JapaneseTokenizer has discardPunctuation set to false. In case punctuation characters, such as ． (U+FF0E FULLWIDTH FULL STOP), is removed from the token stream, this filter would find input tokens tokens ３ and ２千 and give outputs 3 and 2000 instead of 3200, which is likely not the intended result. If you want to remove punctuation characters from your index that are not part of normalized numbers, add a StopFilter with the punctuation you wish to remove after JapaneseNumberFilter in your analyzer chain.

    Below are some examples of normalizations this filter supports. The input is untokenized text and the result is the single term attribute emitted for the input.

    • 〇〇七 becomes 7
    • 一〇〇〇 becomes 1000
    • 三千2百２十三 becomes 3223
    • 兆六百万五千一 becomes 1000006005001
    • ３．２千 becomes 3200
    • １．２万３４５．６７ becomes 12345.67
    • 4,647.100 becomes 4647.1
    • 15,7 becomes 157 (be aware of this weakness)

    Tokens preceded by a token with PositionIncrementAttribute of zero are left left untouched and emitted as-is.

    This filter does not use any part-of-speech information for its normalization and the motivation for this is to also support n-grammed token streams in the future.

    This filter may in some cases normalize tokens that are not numbers in their context. For example, is 田中京一 is a name and means Tanaka Kyōichi, but 京一 (Kyōichi) out of context can strictly speaking also represent the number 10000000000000001. This filter respects the KeywordAttribute, which can be used to prevent specific normalizations from happening.

    Also notice that token attributes such as PartOfSpeechAttribute, ReadingAttribute, InflectionAttribute and BaseFormAttribute are left unchanged and will inherit the values of the last token used to compose the normalized number and can be wrong. Hence, for １０万 (10000), we will have ReadingAttribute set to マン. This is a known issue and is subject to a future improvement.

    Japanese formal numbers (daiji), accounting numbers and decimal fractions are currently not supported.

    • Constructor Detail

      • JapaneseNumberFilter

        public JapaneseNumberFilter​(TokenStream input)

    • Method Detail

      • normalizeNumber

        public String normalizeNumber​(String number)
        Normalizes a Japanese number
        Parameters:
        number - number or normalize
        Returns:
        normalized number, or number to normalize on error (no op)

      • parseLargeKanjiNumeral

        public BigDecimal parseLargeKanjiNumeral​(JapaneseNumberFilter.NumberBuffer buffer)
        Parse large kanji numerals (ten thousands or larger)
        Parameters:
        buffer - buffer to parse
        Returns:
        parsed number, or null on error or end of input

      • parseMediumKanjiNumeral

        public BigDecimal parseMediumKanjiNumeral​(JapaneseNumberFilter.NumberBuffer buffer)
        Parse medium kanji numerals (tens, hundreds or thousands)
        Parameters:
        buffer - buffer to parse
        Returns:
        parsed number or null on error

      • isNumeral

        public boolean isNumeral​(String input)
        Numeral predicate
        Parameters:
        input - string to test
        Returns:
        true if and only if input is a numeral

      • isNumeral

        public boolean isNumeral​(char c)
        Numeral predicate
        Parameters:
        c - character to test
        Returns:
        true if and only if c is a numeral

      • isNumeralPunctuation

        public boolean isNumeralPunctuation​(String input)
        Numeral punctuation predicate
        Parameters:
        input - string to test
        Returns:
        true if and only if c is a numeral punctuation string

      • isNumeralPunctuation

        public boolean isNumeralPunctuation​(char c)
        Numeral punctuation predicate
        Parameters:
        c - character to test
        Returns:
        true if and only if c is a numeral punctuation character

      • isArabicNumeral

        public boolean isArabicNumeral​(char c)
        Arabic numeral predicate. Both half-width and full-width characters are supported
        Parameters:
        c - character to test
        Returns:
        true if and only if c is an Arabic numeral