## org.apache.lucene.analysis.util
Class CharacterUtils

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

    public abstract class CharacterUtils

extends Object

`CharacterUtils` provides a unified interface to Character-related operations to implement backwards compatible character operations based on a `Version` instance.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary
`static class` `CharacterUtils.CharacterBuffer` A simple IO buffer to use with `fill(CharacterBuffer, Reader)`.

Constructor Summary
`CharacterUtils()`

Method Summary
`abstract int` `codePointAt(char[] chars, int offset)` Returns the code point at the given index of the char array.
`abstract int` `codePointAt(char[] chars, int offset, int limit)` Returns the code point at the given index of the char array where only elements with index less than the limit are used.
`abstract int` `codePointAt(CharSequence seq, int offset)` Returns the code point at the given index of the `CharSequence`.
`abstract boolean` `fill(CharacterUtils.CharacterBuffer buffer, Reader reader)` Fills the `CharacterUtils.CharacterBuffer` with characters read from the given reader `Reader`.
`static CharacterUtils` `getInstance(Version matchVersion)` Returns a `CharacterUtils` implementation according to the given `Version` instance.
`static CharacterUtils.CharacterBuffer` `newCharacterBuffer(int bufferSize)` Creates a new `CharacterUtils.CharacterBuffer` and allocates a `char[]` of the given bufferSize.
`void` `toLowerCase(char[] buffer, int offset, int limit)` Converts each unicode codepoint to lowerCase via `Character.toLowerCase(int)` starting at the given offset.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### CharacterUtils

    public CharacterUtils()

Method Detail

### getInstance

    public static CharacterUtils getInstance(Version matchVersion)

  Returns a `CharacterUtils` implementation according to the given `Version` instance.

  Parameters:
    `matchVersion` - a version instance
  Returns:
    a `CharacterUtils` implementation according to the given `Version` instance.

### codePointAt

    public abstract int codePointAt(char[] chars,
                                    int offset)

  Returns the code point at the given index of the char array. Depending on the `Version` passed to `getInstance(Version)` this method mimics the behavior of `Character.codePointAt(char[], int)` as it would have been available on a Java 1.4 JVM or on a later virtual machine version.

  Parameters:
    `chars` - a character array
    `offset` - the offset to the char values in the chars array to be converted
  Returns:
    the Unicode code point at the given index
  Throws:
    `NullPointerException` - - if the array is null.
    `IndexOutOfBoundsException` - - if the value offset is negative or not less than the length of the char array.

### codePointAt

    public abstract int codePointAt(CharSequence seq,
                                    int offset)

  Returns the code point at the given index of the `CharSequence`. Depending on the `Version` passed to `getInstance(Version)` this method mimics the behavior of `Character.codePointAt(char[], int)` as it would have been available on a Java 1.4 JVM or on a later virtual machine version.

  Parameters:
    `seq` - a character sequence
    `offset` - the offset to the char values in the chars array to be converted
  Returns:
    the Unicode code point at the given index
  Throws:
    `NullPointerException` - - if the sequence is null.
    `IndexOutOfBoundsException` - - if the value offset is negative or not less than the length of the character sequence.

### codePointAt

    public abstract int codePointAt(char[] chars,
                                    int offset,
                                    int limit)

  Returns the code point at the given index of the char array where only elements with index less than the limit are used. Depending on the `Version` passed to `getInstance(Version)` this method mimics the behavior of `Character.codePointAt(char[], int)` as it would have been available on a Java 1.4 JVM or on a later virtual machine version.

  Parameters:
    `chars` - a character array
    `offset` - the offset to the char values in the chars array to be converted
    `limit` - the index afer the last element that should be used to calculate codepoint.
  Returns:
    the Unicode code point at the given index
  Throws:
    `NullPointerException` - - if the array is null.
    `IndexOutOfBoundsException` - - if the value offset is negative or not less than the length of the char array.

### 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 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

### fill

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

  Fills the `CharacterUtils.CharacterBuffer` with characters read from the given reader `Reader`. This method tries to read as many characters into the `CharacterUtils.CharacterBuffer` as possible, each call to fill will start filling the buffer from offset `0` up to the length of the size of the internal character array.

  Depending on the `Version` passed to `getInstance(Version)` this method implements supplementary character awareness when filling the given buffer. For all `Version` > 3.0 `fill(CharacterBuffer, Reader)` 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.

  Parameters:
    `buffer` - the buffer to fill.
    `reader` - the reader to read characters from.
  Returns:
    `true` if and only if no more characters are available in the reader, otherwise `false`.
  Throws:
    `IOException` - if the reader throws an `IOException`.

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