Replaceable is an interface representing a
* string of characters that supports the replacement of a range of
* itself with a new string of characters. It is used by APIs that
* change a piece of text while retaining metadata. Metadata is data
* other than the Unicode characters returned by char32At(). One
* example of metadata is style attributes; another is an edit
* history, marking each character with an author and revision number.
*
* An implicit aspect of the Replaceable API is that
* during a replace operation, new characters take on the metadata of
* the old characters. For example, if the string "the bold
* font" has range (4, 8) replaced with "strong", then it becomes "the
* strong font".
*
*
Replaceable specifies ranges using a start
* offset and a limit offset. The range of characters thus specified
* includes the characters at offset start..limit-1. That is, the
* start offset is inclusive, and the limit offset is exclusive.
*
*
Replaceable also includes API to access characters
* in the string: length(), charAt(),
* char32At(), and extractBetween().
*
*
For a subclass to support metadata, typical behavior of
* replace() is the following:
*
length()-1
* inclusive
* @return 16-bit code unit of text at given offset
*/
char charAt(int offset);
/**
* Returns the 32-bit code point at the given 16-bit offset into
* the text. This assumes the text is stored as 16-bit code units
* with surrogate pairs intermixed. If the offset of a leading or
* trailing code unit of a surrogate pair is given, return the
* code point of the surrogate pair.
*
* Most subclasses can return
* android.icu.text.UTF16.charAt(this, offset).
* @param offset an integer between 0 and length()-1
* inclusive
* @return 32-bit code point of text at given offset
*/
int char32At(int offset);
/**
* Copies characters from this object into the destination
* character array. The first character to be copied is at index
* srcStart; the last character to be copied is at
* index srcLimit-1 (thus the total number of
* characters to be copied is srcLimit-srcStart). The
* characters are copied into the subarray of dst
* starting at index dstStart and ending at index
* dstStart + (srcLimit-srcStart) - 1.
*
* @param srcStart the beginning index to copy, inclusive; 0
* <= start <= limit.
* @param srcLimit the ending index to copy, exclusive;
* start <= limit <= length().
* @param dst the destination array.
* @param dstStart the start offset in the destination array.
*/
void getChars(int srcStart, int srcLimit, char dst[], int dstStart);
/**
* Replaces a substring of this object with the given text.
*
*
Subclasses must ensure that if the text between start and
* limit is equal to the replacement text, that replace has no
* effect. That is, any metadata
* should be unaffected. In addition, subclasses are encouraged to
* check for initial and trailing identical characters, and make a
* smaller replacement if possible. This will preserve as much
* metadata as possible.
* @param start the beginning index, inclusive; 0 <= start
* <= limit.
* @param limit the ending index, exclusive; start <= limit
* <= length().
* @param text the text to replace characters start
* to limit - 1
*/
void replace(int start, int limit, String text);
/**
* Replaces a substring of this object with the given text.
*
*
Subclasses must ensure that if the text between start and
* limit is equal to the replacement text, that replace has no
* effect. That is, any metadata
* should be unaffected. In addition, subclasses are encouraged to
* check for initial and trailing identical characters, and make a
* smaller replacement if possible. This will preserve as much
* metadata as possible.
* @param start the beginning index, inclusive; 0 <= start
* <= limit.
* @param limit the ending index, exclusive; start <= limit
* <= length().
* @param chars the text to replace characters start
* to limit - 1
* @param charsStart the beginning index into chars,
* inclusive; 0 <= start <= limit.
* @param charsLen the number of characters of chars.
*/
void replace(int start, int limit, char[] chars,
int charsStart, int charsLen);
// Note: We use length rather than limit to conform to StringBuffer
// and System.arraycopy.
/**
* Copies a substring of this object, retaining metadata.
* This method is used to duplicate or reorder substrings.
* The destination index must not overlap the source range.
* If hasMetaData() returns false, subclasses
* may use the naive implementation:
*
*
char[] text = new char[limit - start];
* getChars(start, limit, text, 0);
* replace(dest, dest, text, 0, limit - start);
*
* @param start the beginning index, inclusive; 0 <= start <=
* limit.
* @param limit the ending index, exclusive; start <= limit <=
* length().
* @param dest the destination index. The characters from
* start..limit-1 will be copied to dest.
* Implementations of this method may assume that dest <= start ||
* dest >= limit.
*/
void copy(int start, int limit, int dest);
/**R
* Returns true if this object contains metadata. If a
* Replaceable object has metadata, calls to the Replaceable API
* must be made so as to preserve metadata. If it does not, calls
* to the Replaceable API may be optimized to improve performance.
* @return true if this object contains metadata
*/
boolean hasMetaData();
}