public final class StringBuffer extends Object implements Serializable, CharSequence, Appendable
StringBuffer
represents a changeable String
.
It provides the operations required to modify the
StringBuffer
, including insert, replace, delete, append,
and reverse. It is thread-safe; meaning that all modifications to a buffer
are in synchronized methods.
StringBuffer
s are variable-length in nature, so even if
you initialize them to a certain size, they can still grow larger than
that. Capacity indicates the number of characters the
StringBuffer
can have in it before it has to grow (growing
the char array is an expensive operation involving new
).
Incidentally, compilers often implement the String operator "+"
by using a StringBuffer
operation:
a + b
is the same as
new StringBuffer().append(a).append(b).toString()
.
Classpath's StringBuffer is capable of sharing memory with Strings for efficiency. This will help when a StringBuffer is converted to a String and the StringBuffer is not changed after that (quite common when performing string concatenation).
String
,
Serialized FormConstructor and Description |
---|
StringBuffer()
Create a new StringBuffer with default capacity 16.
|
StringBuffer(CharSequence seq)
Create a new
StringBuffer with the characters in the
specified CharSequence . |
StringBuffer(int capacity)
Create an empty
StringBuffer with the specified initial
capacity. |
StringBuffer(String str)
Create a new
StringBuffer with the characters in the
specified String . |
Modifier and Type | Method and Description |
---|---|
StringBuffer |
append(boolean bool)
Append the
String value of the argument to this
StringBuffer . |
StringBuffer |
append(char ch)
Append the
char to this StringBuffer . |
StringBuffer |
append(char[] data)
Append the
char array to this StringBuffer . |
StringBuffer |
append(char[] data,
int offset,
int count)
Append part of the
char array to this
StringBuffer . |
StringBuffer |
append(CharSequence seq)
Append the characters in the
CharSequence to this
buffer. |
StringBuffer |
append(CharSequence seq,
int start,
int end)
Append some characters from the
CharSequence to this
buffer. |
StringBuffer |
append(double dnum)
Append the
String value of the argument to this
StringBuffer . |
StringBuffer |
append(float fnum)
Append the
String value of the argument to this
StringBuffer . |
StringBuffer |
append(int inum)
Append the
String value of the argument to this
StringBuffer . |
StringBuffer |
append(long lnum)
Append the
String value of the argument to this
StringBuffer . |
StringBuffer |
append(Object obj)
Append the
String value of the argument to this
StringBuffer . |
StringBuffer |
append(String str)
Append the
String to this StringBuffer . |
StringBuffer |
append(StringBuffer stringBuffer)
Append the
StringBuffer value of the argument to this
StringBuffer . |
StringBuffer |
appendCodePoint(int code)
Append the code point to this
StringBuffer . |
int |
capacity()
Get the total number of characters this
StringBuffer can
support before it must be grown. |
char |
charAt(int index)
Get the character at the specified index.
|
int |
codePointAt(int index)
Get the code point at the specified index.
|
int |
codePointBefore(int index)
Get the code point before the specified index.
|
int |
codePointCount(int start,
int end)
Return the number of code points between two indices in the
StringBuffer . |
StringBuffer |
delete(int start,
int end)
Delete characters from this
StringBuffer . |
StringBuffer |
deleteCharAt(int index)
Delete a character from this
StringBuffer . |
void |
ensureCapacity(int minimumCapacity)
Increase the capacity of this
StringBuffer . |
void |
getChars(int srcOffset,
int srcEnd,
char[] dst,
int dstOffset)
Get the specified array of characters.
|
int |
indexOf(String str)
Finds the first instance of a substring in this StringBuffer.
|
int |
indexOf(String str,
int fromIndex)
Finds the first instance of a String in this StringBuffer, starting at
a given index.
|
StringBuffer |
insert(int offset,
boolean bool)
Insert the
String value of the argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
char ch)
Insert the
char argument into this StringBuffer . |
StringBuffer |
insert(int offset,
char[] data)
Insert the
char[] argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
char[] str,
int str_offset,
int len)
Insert a subarray of the
char[] argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
CharSequence sequence)
Insert the
CharSequence argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
CharSequence sequence,
int start,
int end)
Insert a subsequence of the
CharSequence argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
double dnum)
Insert the
String value of the argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
float fnum)
Insert the
String value of the argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
int inum)
Insert the
String value of the argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
long lnum)
Insert the
String value of the argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
Object obj)
Insert the
String value of the argument into this
StringBuffer . |
StringBuffer |
insert(int offset,
String str)
Insert the
String argument into this
StringBuffer . |
int |
lastIndexOf(String str)
Finds the last instance of a substring in this StringBuffer.
|
int |
lastIndexOf(String str,
int fromIndex)
Finds the last instance of a String in this StringBuffer, starting at a
given index.
|
int |
length()
Get the length of the
String this StringBuffer
would create. |
int |
offsetByCodePoints(int start,
int codePoints)
Starting at the given index, this counts forward by the indicated
number of code points, and then returns the resulting index.
|
StringBuffer |
replace(int start,
int end,
String str)
Replace characters between index
start (inclusive) and
end (exclusive) with str . |
StringBuffer |
reverse()
Reverse the characters in this StringBuffer.
|
void |
setCharAt(int index,
char ch)
Set the character at the specified index.
|
void |
setLength(int newLength)
Set the length of this StringBuffer.
|
CharSequence |
subSequence(int beginIndex,
int endIndex)
Creates a substring of this StringBuffer, starting at a specified index
and ending at one character before a specified index.
|
String |
substring(int beginIndex)
Creates a substring of this StringBuffer, starting at a specified index
and ending at the end of this StringBuffer.
|
String |
substring(int beginIndex,
int endIndex)
Creates a substring of this StringBuffer, starting at a specified index
and ending at one character before a specified index.
|
String |
toString()
Convert this
StringBuffer to a String . |
void |
trimToSize()
This may reduce the amount of memory used by the StringBuffer,
by resizing the internal array to remove unused space.
|
public StringBuffer()
public StringBuffer(int capacity)
StringBuffer
with the specified initial
capacity.capacity
- the initial capacityNegativeArraySizeException
- if capacity is negativepublic StringBuffer(String str)
StringBuffer
with the characters in the
specified String
. Initial capacity will be the size of the
String plus 16.str
- the String
to convertNullPointerException
- if str is nullpublic StringBuffer(CharSequence seq)
StringBuffer
with the characters in the
specified CharSequence
. Initial capacity will be the
length of the sequence plus 16; if the sequence reports a length
less than or equal to 0, then the initial capacity will be 16.seq
- the initializing CharSequence
NullPointerException
- if str is nullpublic int length()
String
this StringBuffer
would create. Not to be confused with the capacity of the
StringBuffer
.length
in interface CharSequence
StringBuffer
capacity()
,
setLength(int)
public int capacity()
StringBuffer
can
support before it must be grown. Not to be confused with length.StringBuffer
length()
,
ensureCapacity(int)
public void ensureCapacity(int minimumCapacity)
StringBuffer
. This will
ensure that an expensive growing operation will not occur until
minimumCapacity
is reached. The buffer is grown to the
larger of minimumCapacity
and
capacity() * 2 + 2
, if it is not already large enough.minimumCapacity
- the new capacitycapacity()
public void setLength(int newLength)
newLength
characters of the old array will be preserved, and the remaining
characters are truncated.newLength
- the new lengthIndexOutOfBoundsException
- if the new length is negative
(while unspecified, this is a StringIndexOutOfBoundsException)length()
public char charAt(int index)
charAt
in interface CharSequence
index
- the index of the character to get, starting at 0IndexOutOfBoundsException
- if index is negative or >= length()
(while unspecified, this is a StringIndexOutOfBoundsException)public int codePointAt(int index)
index
- the index of the codepoint to get, starting at 0IndexOutOfBoundsException
- if index is negative or >= length()public int codePointBefore(int index)
index-1
and
index-2
to see if they form a supplementary code point.index
- the index just past the codepoint to get, starting at 0IndexOutOfBoundsException
- if index is negative or >= length()public void getChars(int srcOffset, int srcEnd, char[] dst, int dstOffset)
srcOffset - srcEnd
characters will be copied into the array you pass in.srcOffset
- the index to start copying from (inclusive)srcEnd
- the index to stop copying from (exclusive)dst
- the array to copy intodstOffset
- the index to start copying intoNullPointerException
- if dst is nullIndexOutOfBoundsException
- if any source or target indices are
out of range (while unspecified, source problems cause a
StringIndexOutOfBoundsException, and dest problems cause an
ArrayIndexOutOfBoundsException)System.arraycopy(Object, int, Object, int, int)
public void setCharAt(int index, char ch)
index
- the index of the character to set starting at 0ch
- the value to set that character toIndexOutOfBoundsException
- if index is negative or >= length()
(while unspecified, this is a StringIndexOutOfBoundsException)public StringBuffer append(Object obj)
String
value of the argument to this
StringBuffer
. Uses String.valueOf()
to convert
to String
.obj
- the Object
to convert and appendStringBuffer
String.valueOf(Object)
,
append(String)
public StringBuffer append(String str)
String
to this StringBuffer
. If
str is null, the String "null" is appended.str
- the String
to appendStringBuffer
public StringBuffer append(StringBuffer stringBuffer)
StringBuffer
value of the argument to this
StringBuffer
. This behaves the same as
append((Object) stringBuffer)
, except it is more efficient.stringBuffer
- the StringBuffer
to convert and appendStringBuffer
append(Object)
public StringBuffer append(char[] data)
char
array to this StringBuffer
.
This is similar (but more efficient) than
append(new String(data))
, except in the case of null.data
- the char[]
to appendStringBuffer
NullPointerException
- if str
is null
append(char[], int, int)
public StringBuffer append(char[] data, int offset, int count)
char
array to this
StringBuffer
. This is similar (but more efficient) than
append(new String(data, offset, count))
, except in the case
of null.data
- the char[]
to appendoffset
- the start location in str
count
- the number of characters to get from str
StringBuffer
NullPointerException
- if str
is null
IndexOutOfBoundsException
- if offset or count is out of range
(while unspecified, this is a StringIndexOutOfBoundsException)public StringBuffer append(boolean bool)
String
value of the argument to this
StringBuffer
. Uses String.valueOf()
to convert
to String
.bool
- the boolean
to convert and appendStringBuffer
String.valueOf(boolean)
public StringBuffer append(char ch)
char
to this StringBuffer
.append
in interface Appendable
ch
- the char
to appendStringBuffer
public StringBuffer append(CharSequence seq)
CharSequence
to this
buffer.append
in interface Appendable
seq
- the CharSequence
providing the charactersStringBuffer
public StringBuffer append(CharSequence seq, int start, int end)
CharSequence
to this
buffer. If the argument is null, the four characters "null" are
appended.append
in interface Appendable
seq
- the CharSequence
providing the charactersstart
- the starting indexend
- one past the final indexStringBuffer
public StringBuffer append(int inum)
String
value of the argument to this
StringBuffer
. Uses String.valueOf()
to convert
to String
.inum
- the int
to convert and appendStringBuffer
String.valueOf(int)
public StringBuffer append(long lnum)
String
value of the argument to this
StringBuffer
. Uses String.valueOf()
to convert
to String
.lnum
- the long
to convert and appendStringBuffer
String.valueOf(long)
public StringBuffer append(float fnum)
String
value of the argument to this
StringBuffer
. Uses String.valueOf()
to convert
to String
.fnum
- the float
to convert and appendStringBuffer
String.valueOf(float)
public StringBuffer append(double dnum)
String
value of the argument to this
StringBuffer
. Uses String.valueOf()
to convert
to String
.dnum
- the double
to convert and appendStringBuffer
String.valueOf(double)
public StringBuffer appendCodePoint(int code)
StringBuffer
.
This is like #append(char), but will append two characters
if a supplementary code point is given.code
- the code point to appendStringBuffer
Character.toChars(int, char[], int)
public StringBuffer delete(int start, int end)
StringBuffer
.
delete(10, 12)
will delete 10 and 11, but not 12. It is
harmless for end to be larger than length().start
- the first character to deleteend
- the index after the last character to deleteStringBuffer
StringIndexOutOfBoundsException
- if start or end are out of boundspublic StringBuffer deleteCharAt(int index)
StringBuffer
.index
- the index of the character to deleteStringBuffer
StringIndexOutOfBoundsException
- if index is out of boundspublic StringBuffer replace(int start, int end, String str)
start
(inclusive) and
end
(exclusive) with str
. If end
is larger than the size of this StringBuffer, all characters after
start
are replaced.start
- the beginning index of characters to delete (inclusive)end
- the ending index of characters to delete (exclusive)str
- the new String
to insertStringBuffer
StringIndexOutOfBoundsException
- if start or end are out of boundsNullPointerException
- if str is nullpublic String substring(int beginIndex)
beginIndex
- index to start substring (base 0)StringIndexOutOfBoundsException
- if beginIndex is out of boundssubstring(int, int)
public CharSequence subSequence(int beginIndex, int endIndex)
substring(beginIndex, endIndex)
, to satisfy
the CharSequence interface.subSequence
in interface CharSequence
beginIndex
- index to start at (inclusive, base 0)endIndex
- index to end at (exclusive)IndexOutOfBoundsException
- if beginIndex or endIndex is out of
boundssubstring(int, int)
public String substring(int beginIndex, int endIndex)
beginIndex
- index to start at (inclusive, base 0)endIndex
- index to end at (exclusive)StringIndexOutOfBoundsException
- if beginIndex or endIndex is out
of boundspublic StringBuffer insert(int offset, char[] str, int str_offset, int len)
char[]
argument into this
StringBuffer
.offset
- the place to insert in this bufferstr
- the char[]
to insertstr_offset
- the index in str
to start inserting fromlen
- the number of characters to insertStringBuffer
NullPointerException
- if str
is null
StringIndexOutOfBoundsException
- if any index is out of boundspublic StringBuffer insert(int offset, Object obj)
String
value of the argument into this
StringBuffer
. Uses String.valueOf()
to convert
to String
.offset
- the place to insert in this bufferobj
- the Object
to convert and insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundsString.valueOf(Object)
public StringBuffer insert(int offset, String str)
String
argument into this
StringBuffer
. If str is null, the String "null" is used
instead.offset
- the place to insert in this bufferstr
- the String
to insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundspublic StringBuffer insert(int offset, CharSequence sequence)
CharSequence
argument into this
StringBuffer
. If the sequence is null, the String
"null" is used instead.offset
- the place to insert in this buffersequence
- the CharSequence
to insertStringBuffer
IndexOutOfBoundsException
- if offset is out of boundspublic StringBuffer insert(int offset, CharSequence sequence, int start, int end)
CharSequence
argument into this
StringBuffer
. If the sequence is null, the String
"null" is used instead.offset
- the place to insert in this buffersequence
- the CharSequence
to insertstart
- the starting index of the subsequenceend
- one past the ending index of the subsequenceStringBuffer
IndexOutOfBoundsException
- if offset, start,
or end are out of boundspublic StringBuffer insert(int offset, char[] data)
char[]
argument into this
StringBuffer
.offset
- the place to insert in this bufferdata
- the char[]
to insertStringBuffer
NullPointerException
- if data
is null
StringIndexOutOfBoundsException
- if offset is out of boundsinsert(int, char[], int, int)
public StringBuffer insert(int offset, boolean bool)
String
value of the argument into this
StringBuffer
. Uses String.valueOf()
to convert
to String
.offset
- the place to insert in this bufferbool
- the boolean
to convert and insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundsString.valueOf(boolean)
public StringBuffer insert(int offset, char ch)
char
argument into this StringBuffer
.offset
- the place to insert in this bufferch
- the char
to insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundspublic StringBuffer insert(int offset, int inum)
String
value of the argument into this
StringBuffer
. Uses String.valueOf()
to convert
to String
.offset
- the place to insert in this bufferinum
- the int
to convert and insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundsString.valueOf(int)
public StringBuffer insert(int offset, long lnum)
String
value of the argument into this
StringBuffer
. Uses String.valueOf()
to convert
to String
.offset
- the place to insert in this bufferlnum
- the long
to convert and insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundsString.valueOf(long)
public StringBuffer insert(int offset, float fnum)
String
value of the argument into this
StringBuffer
. Uses String.valueOf()
to convert
to String
.offset
- the place to insert in this bufferfnum
- the float
to convert and insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundsString.valueOf(float)
public StringBuffer insert(int offset, double dnum)
String
value of the argument into this
StringBuffer
. Uses String.valueOf()
to convert
to String
.offset
- the place to insert in this bufferdnum
- the double
to convert and insertStringBuffer
StringIndexOutOfBoundsException
- if offset is out of boundsString.valueOf(double)
public int indexOf(String str)
str
- String to findNullPointerException
- if str is nullindexOf(String, int)
public int indexOf(String str, int fromIndex)
str
- String to findfromIndex
- index to start the searchNullPointerException
- if str is nullpublic int lastIndexOf(String str)
str
- String to findNullPointerException
- if str is nulllastIndexOf(String, int)
public int lastIndexOf(String str, int fromIndex)
str
- String to findfromIndex
- index to start the searchNullPointerException
- if str is nullpublic StringBuffer reverse()
StringBuffer
public String toString()
StringBuffer
to a String
. The
String is composed of the characters currently in this StringBuffer. Note
that the result is a copy, and that future modifications to this buffer
do not affect the String.toString
in interface CharSequence
toString
in class Object
Object.getClass()
,
Object.hashCode()
,
Class.getName()
,
Integer.toHexString(int)
public void trimToSize()
public int codePointCount(int start, int end)
StringBuffer
. An unpaired surrogate counts as a
code point for this purpose. Characters outside the indicated
range are not examined, even if the range ends in the middle of a
surrogate pair.start
- the starting indexend
- one past the ending indexpublic int offsetByCodePoints(int start, int codePoints)
start
- the starting indexcodePoints
- the number of code points