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java.lang.Objectjava.lang.StringBuilder
public final class StringBuilder
StringBuilder represents a changeable String.
It provides the operations required to modify the
StringBuilder, including insert, replace, delete, append,
and reverse. It like StringBuffer, but is not
synchronized. It is ideal for use when it is known that the
object will only be used from a single thread.
StringBuilders 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
StringBuilder 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 StringBuilder operation:
a + b
is the same as
new StringBuilder().append(a).append(b).toString().
Classpath's StringBuilder is capable of sharing memory with Strings for efficiency. This will help when a StringBuilder is converted to a String and the StringBuilder is not changed after that (quite common when performing string concatenation).
String,
StringBuffer,
Serialized Form| Constructor Summary | |
|---|---|
StringBuilder()
Create a new StringBuilder with default capacity 16. |
|
StringBuilder(CharSequence seq)
Create a new StringBuilder with the characters in the
specified CharSequence. |
|
StringBuilder(int capacity)
Create an empty StringBuilder with the specified initial
capacity. |
|
StringBuilder(String str)
Create a new StringBuilder with the characters in the
specified String. |
|
| Method Summary | |
|---|---|
StringBuilder |
append(boolean bool)
Append the String value of the argument to this
StringBuilder. |
StringBuilder |
append(char ch)
Append the char to this StringBuilder. |
StringBuilder |
append(char[] data)
Append the char array to this StringBuilder. |
StringBuilder |
append(char[] data,
int offset,
int count)
Append part of the char array to this
StringBuilder. |
StringBuilder |
append(CharSequence seq)
Append the characters in the CharSequence to this
buffer. |
StringBuilder |
append(CharSequence seq,
int start,
int end)
Append some characters from the CharSequence to this
buffer. |
StringBuilder |
append(double dnum)
Append the String value of the argument to this
StringBuilder. |
StringBuilder |
append(float fnum)
Append the String value of the argument to this
StringBuilder. |
StringBuilder |
append(int inum)
Append the String value of the argument to this
StringBuilder. |
StringBuilder |
append(long lnum)
Append the String value of the argument to this
StringBuilder. |
StringBuilder |
append(Object obj)
Append the String value of the argument to this
StringBuilder. |
StringBuilder |
append(String str)
Append the String to this StringBuilder. |
StringBuilder |
append(StringBuffer stringBuffer)
Append the StringBuilder value of the argument to this
StringBuilder. |
StringBuilder |
appendCodePoint(int code)
Append the code point to this StringBuilder. |
int |
capacity()
Get the total number of characters this StringBuilder 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. |
StringBuilder |
delete(int start,
int end)
Delete characters from this StringBuilder. |
StringBuilder |
deleteCharAt(int index)
Delete a character from this StringBuilder. |
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 StringBuilder. |
int |
indexOf(String str,
int fromIndex)
Finds the first instance of a String in this StringBuffer, starting at a given index. |
StringBuilder |
insert(int offset,
boolean bool)
Insert the String value of the argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
char ch)
Insert the char argument into this StringBuilder. |
StringBuilder |
insert(int offset,
char[] data)
Insert the char[] argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
char[] str,
int str_offset,
int len)
Insert a subarray of the char[] argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
CharSequence sequence)
Insert the CharSequence argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
CharSequence sequence,
int start,
int end)
Insert a subsequence of the CharSequence argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
double dnum)
Insert the String value of the argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
float fnum)
Insert the String value of the argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
int inum)
Insert the String value of the argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
long lnum)
Insert the String value of the argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
Object obj)
Insert the String value of the argument into this
StringBuilder. |
StringBuilder |
insert(int offset,
String str)
Insert the String argument into this
StringBuilder. |
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 StringBuilder
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. |
StringBuilder |
replace(int start,
int end,
String str)
Replace characters between index start (inclusive) and
end (exclusive) with str. |
StringBuilder |
reverse()
Reverse the characters in this StringBuilder. |
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 StringBuilder, starting at a specified index and ending at one character before a specified index. |
String |
substring(int beginIndex)
Creates a substring of this StringBuilder, starting at a specified index and ending at the end of this StringBuilder. |
String |
substring(int beginIndex,
int endIndex)
Creates a substring of this StringBuilder, starting at a specified index and ending at one character before a specified index. |
String |
toString()
Convert this StringBuilder 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. |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface java.lang.CharSequence |
|---|
charAt |
| Constructor Detail |
|---|
public StringBuilder()
public StringBuilder(int capacity)
StringBuilder with the specified initial
capacity.
capacity - the initial capacity
NegativeArraySizeException - if capacity is negativepublic StringBuilder(String str)
StringBuilder with the characters in the
specified String. Initial capacity will be the size of the
String plus 16.
str - the String to convert
NullPointerException - if str is nullpublic StringBuilder(CharSequence seq)
StringBuilder 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 null| Method Detail |
|---|
public int length()
String this StringBuilder
would create. Not to be confused with the capacity of the
StringBuilder.
length in interface CharSequenceStringBuildercapacity(),
setLength(int)public int capacity()
StringBuilder can
support before it must be grown. Not to be confused with length.
StringBuilderlength(),
ensureCapacity(int)public StringBuilder append(Object obj)
String value of the argument to this
StringBuilder. Uses String.valueOf() to convert
to String.
obj - the Object to convert and append
StringBuilderString.valueOf(Object),
append(String)public StringBuilder append(String str)
String to this StringBuilder. If
str is null, the String "null" is appended.
str - the String to append
StringBuilderpublic StringBuilder append(StringBuffer stringBuffer)
StringBuilder value of the argument to this
StringBuilder. This behaves the same as
append((Object) stringBuffer), except it is more efficient.
stringBuffer - the StringBuilder to convert and append
StringBuilderappend(Object)public StringBuilder append(char[] data)
char array to this StringBuilder.
This is similar (but more efficient) than
append(new String(data)), except in the case of null.
data - the char[] to append
StringBuilder
NullPointerException - if str is nullappend(char[], int, int)
public StringBuilder append(char[] data,
int offset,
int count)
char array to this
StringBuilder. 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 strcount - the number of characters to get from str
StringBuilder
NullPointerException - if str is null
IndexOutOfBoundsException - if offset or count is out of range
(while unspecified, this is a StringIndexOutOfBoundsException)public StringBuilder append(boolean bool)
String value of the argument to this
StringBuilder. Uses String.valueOf() to convert
to String.
bool - the boolean to convert and append
StringBuilderString.valueOf(boolean)public StringBuilder append(char ch)
char to this StringBuilder.
append in interface Appendablech - the char to append
StringBuilderpublic StringBuilder append(CharSequence seq)
CharSequence to this
buffer.
append in interface Appendableseq - the CharSequence providing the characters
StringBuilder
public StringBuilder 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 Appendableseq - the CharSequence providing the charactersstart - the starting indexend - one past the final index
StringBuilderpublic StringBuilder append(int inum)
String value of the argument to this
StringBuilder. Uses String.valueOf() to convert
to String.
inum - the int to convert and append
StringBuilderString.valueOf(int)public StringBuilder append(long lnum)
String value of the argument to this
StringBuilder. Uses String.valueOf() to convert
to String.
lnum - the long to convert and append
StringBuilderString.valueOf(long)public StringBuilder append(float fnum)
String value of the argument to this
StringBuilder. Uses String.valueOf() to convert
to String.
fnum - the float to convert and append
StringBuilderString.valueOf(float)public StringBuilder append(double dnum)
String value of the argument to this
StringBuilder. Uses String.valueOf() to convert
to String.
dnum - the double to convert and append
StringBuilderString.valueOf(double)public StringBuilder appendCodePoint(int code)
StringBuilder.
This is like #append(char), but will append two characters
if a supplementary code point is given.
code - the code point to append
StringBuilderCharacter.toChars(int, char[], int)
public StringBuilder delete(int start,
int end)
StringBuilder.
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 delete
StringBuilder
StringIndexOutOfBoundsException - if start or end are out of boundspublic StringBuilder deleteCharAt(int index)
StringBuilder.
index - the index of the character to delete
StringBuilder
StringIndexOutOfBoundsException - if index is out of bounds
public StringBuilder replace(int start,
int end,
String str)
start (inclusive) and
end (exclusive) with str. If end
is larger than the size of this StringBuilder, 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 insert
StringBuilder
StringIndexOutOfBoundsException - if start or end are out of bounds
NullPointerException - 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 CharSequencebeginIndex - 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 bounds
public StringBuilder insert(int offset,
char[] str,
int str_offset,
int len)
char[] argument into this
StringBuilder.
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 insert
StringBuilder
NullPointerException - if str is null
StringIndexOutOfBoundsException - if any index is out of bounds
public StringBuilder insert(int offset,
Object obj)
String value of the argument into this
StringBuilder. Uses String.valueOf() to convert
to String.
offset - the place to insert in this bufferobj - the Object to convert and insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of boundsString.valueOf(Object)
public StringBuilder insert(int offset,
String str)
String argument into this
StringBuilder. If str is null, the String "null" is used
instead.
offset - the place to insert in this bufferstr - the String to insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of bounds
public StringBuilder insert(int offset,
CharSequence sequence)
CharSequence argument into this
StringBuilder. If the sequence is null, the String
"null" is used instead.
offset - the place to insert in this buffersequence - the CharSequence to insert
StringBuilder
IndexOutOfBoundsException - if offset is out of bounds
public StringBuilder insert(int offset,
CharSequence sequence,
int start,
int end)
CharSequence argument into this
StringBuilder. 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 subsequence
StringBuilder
IndexOutOfBoundsException - if offset, start,
or end are out of bounds
public StringBuilder insert(int offset,
char[] data)
char[] argument into this
StringBuilder.
offset - the place to insert in this bufferdata - the char[] to insert
StringBuilder
NullPointerException - if data is null
StringIndexOutOfBoundsException - if offset is out of boundsinsert(int, char[], int, int)
public StringBuilder insert(int offset,
boolean bool)
String value of the argument into this
StringBuilder. Uses String.valueOf() to convert
to String.
offset - the place to insert in this bufferbool - the boolean to convert and insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of boundsString.valueOf(boolean)
public StringBuilder insert(int offset,
char ch)
char argument into this StringBuilder.
offset - the place to insert in this bufferch - the char to insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of bounds
public StringBuilder insert(int offset,
int inum)
String value of the argument into this
StringBuilder. Uses String.valueOf() to convert
to String.
offset - the place to insert in this bufferinum - the int to convert and insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of boundsString.valueOf(int)
public StringBuilder insert(int offset,
long lnum)
String value of the argument into this
StringBuilder. Uses String.valueOf() to convert
to String.
offset - the place to insert in this bufferlnum - the long to convert and insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of boundsString.valueOf(long)
public StringBuilder insert(int offset,
float fnum)
String value of the argument into this
StringBuilder. Uses String.valueOf() to convert
to String.
offset - the place to insert in this bufferfnum - the float to convert and insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of boundsString.valueOf(float)
public StringBuilder insert(int offset,
double dnum)
String value of the argument into this
StringBuilder. Uses String.valueOf() to convert
to String.
offset - the place to insert in this bufferdnum - the double to convert and insert
StringBuilder
StringIndexOutOfBoundsException - if offset is out of boundsString.valueOf(double)public StringBuilder reverse()
StringBuilderpublic String toString()
StringBuilder to a String. The
String is composed of the characters currently in this StringBuilder. Note
that the result is a copy, and that future modifications to this buffer
do not affect the String.
toString in interface CharSequencetoString in class ObjectObject.getClass(),
Object.hashCode(),
Class.getName(),
Integer.toHexString(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 capacity#capacity()public void setLength(int newLength)
newLength
characters of the old array will be preserved, and the remaining
characters are truncated.
newLength - the new length
IndexOutOfBoundsException - if the new length is negative
(while unspecified, this is a StringIndexOutOfBoundsException)CharSequence.length()public char charAt(int index)
charAt in interface CharSequenceindex - the index of the character to get, starting at 0
IndexOutOfBoundsException - 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 0
IndexOutOfBoundsException - 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 0
IndexOutOfBoundsException - 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 into
NullPointerException - if dst is null
IndexOutOfBoundsException - 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 to
IndexOutOfBoundsException - if index is negative or >= length()
(while unspecified, this is a StringIndexOutOfBoundsException)public int indexOf(String str)
str - String to find
NullPointerException - if str is nullindexOf(String, int)
public int indexOf(String str,
int fromIndex)
str - String to findfromIndex - index to start the search
NullPointerException - if str is nullpublic int lastIndexOf(String str)
str - String to find
NullPointerException - if str is nulllastIndexOf(String, int)
public int lastIndexOf(String str,
int fromIndex)
str - String to findfromIndex - index to start the search
NullPointerException - if str is nullpublic 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 index
public int offsetByCodePoints(int start,
int codePoints)
start - the starting indexcodePoints - the number of code points
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