Replaceable
public
interface
Replaceable
| android.icu.text.Replaceable |
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:
- Set the metadata of the new text to the metadata of the first character replaced
- If no characters are replaced, use the metadata of the previous character
- If there is no previous character (i.e. start == 0), use the following character
- If there is no following character (i.e. the replaceable was
empty), use default metadata
- If the code point U+FFFF is seen, it should be interpreted as a special marker having no metadata
Summary
Public methods | |
|---|---|
abstract
int
|
char32At(int offset)
Returns the 32-bit code point at the given 16-bit offset into the text. |
abstract
char
|
charAt(int offset)
Returns the 16-bit code unit at the given offset into the text. |
abstract
void
|
copy(int start, int limit, int dest)
Copies a substring of this object, retaining metadata. |
abstract
void
|
getChars(int srcStart, int srcLimit, char[] dst, int dstStart)
Copies characters from this object into the destination character array. |
abstract
boolean
|
hasMetaData()
R Returns true if this object contains metadata. |
abstract
int
|
length()
Returns the number of 16-bit code units in the text. |
abstract
void
|
replace(int start, int limit, char[] chars, int charsStart, int charsLen)
Replaces a substring of this object with the given text. |
abstract
void
|
replace(int start, int limit, String text)
Replaces a substring of this object with the given text. |
Public methods
char32At
public abstract int char32At (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).
| Parameters | |
|---|---|
offset |
int: an integer between 0 and length()-1
inclusive |
| Returns | |
|---|---|
int |
32-bit code point of text at given offset |
charAt
public abstract char charAt (int offset)
Returns the 16-bit code unit at the given offset into the text.
| Parameters | |
|---|---|
offset |
int: an integer between 0 and length()-1
inclusive |
| Returns | |
|---|---|
char |
16-bit code unit of text at given offset |
copy
public abstract void copy (int start,
int limit,
int dest)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);
| Parameters | |
|---|---|
start |
int: the beginning index, inclusive; 0 <= start <=
limit. |
limit |
int: the ending index, exclusive; start <= limit <=
length(). |
dest |
int: 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. |
getChars
public abstract void getChars (int srcStart,
int srcLimit,
char[] dst,
int dstStart)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.
| Parameters | |
|---|---|
srcStart |
int: the beginning index to copy, inclusive; 0
<= start <= limit. |
srcLimit |
int: the ending index to copy, exclusive;
start <= limit <= length(). |
dst |
char: the destination array. |
dstStart |
int: the start offset in the destination array. |
hasMetaData
public abstract boolean hasMetaData ()
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.
| Returns | |
|---|---|
boolean |
true if this object contains metadata |
length
public abstract int length ()
Returns the number of 16-bit code units in the text.
| Returns | |
|---|---|
int |
number of 16-bit code units in text |
replace
public abstract void replace (int start,
int limit,
char[] chars,
int charsStart,
int charsLen)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.
| Parameters | |
|---|---|
start |
int: the beginning index, inclusive; 0 <= start
<= limit. |
limit |
int: the ending index, exclusive; start <= limit
<= length(). |
chars |
char: the text to replace characters start
to limit - 1 |
charsStart |
int: the beginning index into chars,
inclusive; 0 <= start <= limit. |
charsLen |
int: the number of characters of chars. |
replace
public abstract 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.
| Parameters | |
|---|---|
start |
int: the beginning index, inclusive; 0 <= start
<= limit. |
limit |
int: the ending index, exclusive; start <= limit
<= length(). |
text |
String: the text to replace characters start
to limit - 1 |