org.apache.lucene.analysis

## Class CharacterUtils

- java.lang.Object
- - org.apache.lucene.analysis.CharacterUtils

-     public final class CharacterUtils
      extends Object

  Utility class to write tokenizers or token filters.
  NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `CharacterUtils.CharacterBuffer` A simple IO buffer to use with `fill(CharacterBuffer, Reader)`.

  - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static boolean` | `fill(CharacterUtils.CharacterBuffer buffer, Reader reader)` Convenience method which calls `fill(buffer, reader, buffer.buffer.length)`.
    `static boolean` | `fill(CharacterUtils.CharacterBuffer buffer, Reader reader, int numChars)` Fills the `CharacterUtils.CharacterBuffer` with characters read from the given reader `Reader`.
    `static CharacterUtils.CharacterBuffer` | `newCharacterBuffer(int bufferSize)` Creates a new `CharacterUtils.CharacterBuffer` and allocates a `char[]` of the given bufferSize.
    `static int` | `toChars(int[] src, int srcOff, int srcLen, char[] dest, int destOff)` Converts a sequence of unicode code points to a sequence of Java characters.
    `static int` | `toCodePoints(char[] src, int srcOff, int srcLen, int[] dest, int destOff)` Converts a sequence of Java characters to a sequence of unicode code points.
    `static void` | `toLowerCase(char[] buffer, int offset, int limit)` Converts each unicode codepoint to lowerCase via `Character.toLowerCase(int)` starting at the given offset.
    `static void` | `toUpperCase(char[] buffer, int offset, int limit)` Converts each unicode codepoint to UpperCase via `Character.toUpperCase(int)` starting at the given offset.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### newCharacterBuffer

          public static CharacterUtils.CharacterBuffer newCharacterBuffer(int bufferSize)

      Creates a new `CharacterUtils.CharacterBuffer` and allocates a `char[]` of the given bufferSize.
      Parameters:
        `bufferSize` - the internal char buffer size, must be `>= 2`
      Returns:
        a new `CharacterUtils.CharacterBuffer` instance.

    - #### toLowerCase

          public static void toLowerCase(char[] buffer,
                                         int offset,
                                         int limit)

      Converts each unicode codepoint to lowerCase via `Character.toLowerCase(int)` starting at the given offset.
      Parameters:
        `buffer` - the char buffer to lowercase
        `offset` - the offset to start at
        `limit` - the max char in the buffer to lower case

    - #### toUpperCase

          public static void toUpperCase(char[] buffer,
                                         int offset,
                                         int limit)

      Converts each unicode codepoint to UpperCase via `Character.toUpperCase(int)` starting at the given offset.
      Parameters:
        `buffer` - the char buffer to UPPERCASE
        `offset` - the offset to start at
        `limit` - the max char in the buffer to lower case

    - #### toCodePoints

          public static int toCodePoints(char[] src,
                                         int srcOff,
                                         int srcLen,
                                         int[] dest,
                                         int destOff)

      Converts a sequence of Java characters to a sequence of unicode code points.
      Returns:
        the number of code points written to the destination buffer

    - #### toChars

          public static int toChars(int[] src,
                                    int srcOff,
                                    int srcLen,
                                    char[] dest,
                                    int destOff)

      Converts a sequence of unicode code points to a sequence of Java characters.
      Returns:
        the number of chars written to the destination buffer

    - #### fill

          public static boolean fill(CharacterUtils.CharacterBuffer buffer,
                                     Reader reader,
                                     int numChars)
                              throws IOException

      Fills the `CharacterUtils.CharacterBuffer` with characters read from the given reader `Reader`. This method tries to read `numChars` characters into the `CharacterUtils.CharacterBuffer`, each call to fill will start filling the buffer from offset `0` up to `numChars`. In case code points can span across 2 java characters, this method may only fill `numChars - 1` characters in order not to split in the middle of a surrogate pair, even if there are remaining characters in the `Reader`.

      This method guarantees that the given `CharacterUtils.CharacterBuffer` will never contain a high surrogate character as the last element in the buffer unless it is the last available character in the reader. In other words, high and low surrogate pairs will always be preserved across buffer boarders.

      A return value of `false` means that this method call exhausted the reader, but there may be some bytes which have been read, which can be verified by checking whether `buffer.getLength() > 0`.

      Parameters:
        `buffer` - the buffer to fill.
        `reader` - the reader to read characters from.
        `numChars` - the number of chars to read
      Returns:
        `false` if and only if reader.read returned -1 while trying to fill the buffer
      Throws:
        `IOException` - if the reader throws an `IOException`.

    - #### fill

          public static boolean fill(CharacterUtils.CharacterBuffer buffer,
                                     Reader reader)
                              throws IOException

      Convenience method which calls `fill(buffer, reader, buffer.buffer.length)`.
      Throws:
        `IOException`

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