java.lang.Object java.lang.StringBuffer
public final class StringBuffer
A thread-safe, mutable sequence of characters. A string buffer is like a String , but can be modified. At any point in time it contains some particular sequence of characters, but the length and content of the sequence can be changed through certain method calls.
String buffers are safe for use by multiple threads. The methods are synchronized where necessary so that all the operations on any particular instance behave as if they occur in some serial order that is consistent with the order of the method calls made by each of the individual threads involved.
The principal operations on a StringBuffer are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string buffer. The append method always adds these characters at the end of the buffer; the insert method adds the characters at a specified point.
For example, if z refers to a string buffer object whose current contents are "start", then the method call z.append("le") would cause the string buffer to contain "startle", whereas z.insert(4, "le") would alter the string buffer to contain "starlet".
In general, if sb refers to an instance of a StringBuffer, then sb.append(x) has the same effect as sb.insert(sb.length(), x).
Whenever an operation occurs involving a source sequence (such as appending or inserting from a source sequence) this class synchronizes only on the string buffer performing the operation, not on the source.
Every string buffer has a capacity. As long as the length of the character sequence contained in the string buffer does not exceed the capacity, it is not necessary to allocate a new internal buffer array. If the internal buffer overflows, it is automatically made larger. As of release
JDK 5,
1.5,
this class has been supplemented with an equivalent class designed for use by a single thread,
StringBuilder
. The
StringBuilder
class should generally be used in preference to this one, as it supports all of the same operations but it is faster, as it performs no synchronization.
Constructor Summary | |
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StringBuffer
() Constructs a string buffer with no characters in it and an initial capacity of 16 characters. |
|
StringBuffer
(
CharSequence
seq) Constructs a string buffer that contains the same characters as the specified CharSequence. |
|
StringBuffer
(int capacity) Constructs a string buffer with no characters in it and the specified initial capacity. |
|
StringBuffer
(
String
str) Constructs a string buffer initialized to the contents of the specified string. |
Method Summary | |
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StringBuffer |
append
(boolean b) Appends the string representation of the boolean argument to the sequence. |
StringBuffer |
append
(char c) Appends the string representation of the char argument to this sequence. |
StringBuffer |
append
(char[] str) Appends the string representation of the char array argument to this sequence. |
StringBuffer |
append
(char[] str, int offset, int len) Appends the string representation of a subarray of the char array argument to this sequence. |
StringBuffer |
append
(
CharSequence
s) Appends the specified CharSequence to this sequence. |
StringBuffer |
append
(
CharSequence
s, int start, int end) Appends a subsequence of the specified CharSequence to this sequence. |
StringBuffer |
append
(double d) Appends the string representation of the double argument to this sequence. |
StringBuffer |
append
(float f) Appends the string representation of the float argument to this sequence. |
StringBuffer |
append
(int i) Appends the string representation of the int argument to this sequence. |
StringBuffer |
append
(long lng) Appends the string representation of the long argument to this sequence. |
StringBuffer |
append
(
Object
obj) Appends the string representation of the Object argument. |
StringBuffer |
append
(
String
str) Appends the specified string to this character sequence. |
StringBuffer |
append
(
StringBuffer
sb) Appends the specified StringBuffer to this sequence. |
StringBuffer |
appendCodePoint
(int codePoint) Appends the string representation of the codePoint argument to this sequence. |
int |
capacity
() Returns the current capacity. |
char |
charAt
(int index) Returns the char value in this sequence at the specified index. |
int |
codePointAt
(int index) Returns the character (Unicode code point) at the specified index. |
int |
codePointBefore
(int index) Returns the character (Unicode code point) before the specified index. |
int |
codePointCount
(int beginIndex, int endIndex) Returns the number of Unicode code points in the specified text range of this sequence. |
StringBuffer |
delete
(int start, int end) Removes the characters in a substring of this sequence. |
StringBuffer |
deleteCharAt
(int index) Removes the char at the specified position in this sequence. |
void |
ensureCapacity
(int minimumCapacity) Ensures that the capacity is at least equal to the specified minimum. |
void |
getChars
(int srcBegin, int srcEnd, char[] dst, int dstBegin) Characters are copied from this sequence into the destination character array dst. |
int |
indexOf
(
String
str) Returns the index within this string of the first occurrence of the specified substring. |
int |
indexOf
(
String
str, int fromIndex) Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. |
StringBuffer |
insert
(int offset, boolean b) Inserts the string representation of the boolean argument into this sequence. |
StringBuffer |
insert
(int offset, char c) Inserts the string representation of the char argument into this sequence. |
StringBuffer |
insert
(int offset, char[] str) Inserts the string representation of the char array argument into this sequence. |
StringBuffer |
insert
(int index, char[] str, int offset, int len) Inserts the string representation of a subarray of the str array argument into this sequence. |
StringBuffer |
insert
(int dstOffset,
CharSequence
s) Inserts the specified CharSequence into this sequence. |
StringBuffer |
insert
(int dstOffset,
CharSequence
s, int start, int end) Inserts a subsequence of the specified CharSequence into this sequence. |
StringBuffer |
insert
(int offset, double d) Inserts the string representation of the double argument into this sequence. |
StringBuffer |
insert
(int offset, float f) Inserts the string representation of the float argument into this sequence. |
StringBuffer |
insert
(int offset, int i) Inserts the string representation of the second int argument into this sequence. |
StringBuffer |
insert
(int offset, long l) Inserts the string representation of the long argument into this sequence. |
StringBuffer |
insert
(int offset,
Object
obj) Inserts the string representation of the Object argument into this character sequence. |
StringBuffer |
insert
(int offset,
String
str) Inserts the string into this character sequence. |
int |
lastIndexOf
(
String
str) Returns the index within this string of the rightmost occurrence of the specified substring. |
int |
lastIndexOf
(
String
str, int fromIndex) Returns the index within this string of the last occurrence of the specified substring. |
int |
length
() Returns the length (character count). |
int |
offsetByCodePoints
(int index, int codePointOffset) Returns the index within this sequence that is offset from the given index by codePointOffset code points. |
StringBuffer |
replace
(int start, int end,
String
str) Replaces the characters in a substring of this sequence with characters in the specified String. |
StringBuffer |
reverse
() Causes this character sequence to be replaced by the reverse of the sequence. |
void |
setCharAt
(int index, char ch) The character at the specified index is set to ch. |
void |
setLength
(int newLength) Sets the length of the character sequence. |
CharSequence |
subSequence
(int start, int end) Returns a new character sequence that is a subsequence of this sequence. |
String |
substring
(int start) Returns a new String that contains a subsequence of characters currently contained in this character sequence. |
String |
substring
(int start, int end) Returns a new String that contains a subsequence of characters currently contained in this sequence. |
String |
toString
() Returns a string representing the data in this sequence. |
void |
trimToSize
() Attempts to reduce storage used for the character sequence. |
Methods inherited from class java.lang. Object |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , wait , wait , wait |
Constructor Detail |
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public StringBuffer()
public StringBuffer(int capacity)
public StringBuffer(String str)
public StringBuffer(CharSequence seq)
If the length of the specified CharSequence is less than or equal to zero, then an empty buffer of capacity 16 is returned.
Method Detail |
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public int length()
public int capacity()
public void ensureCapacity(int minimumCapacity)
public void trimToSize()
public void setLength(int newLength)
If the newLength argument is greater than or equal to the current length, sufficient null characters ('\u0000') are appended so that length becomes the newLength argument.
The newLength argument must be greater than or equal to 0.
public char charAt(int index)
The index argument must be greater than or equal to 0, and less than the length of this sequence.
If the char value specified by the index is a surrogate , the surrogate value is returned.
public int codePointAt(int index)
If the char value specified at the given index is in the high-surrogate range, the following index is less than the length of this sequence, and the char value at the following index is in the low-surrogate range, then the supplementary code point corresponding to this surrogate pair is returned. Otherwise, the char value at the given index is returned.
public int codePointBefore(int index)
If the char value at (index - 1) is in the low-surrogate range, (index - 2) is not negative, and the char value at (index - 2) is in the high-surrogate range, then the supplementary code point value of the surrogate pair is returned. If the char value at index - 1 is an unpaired low-surrogate or a high-surrogate, the surrogate value is returned.
public int codePointCount(int beginIndex, int endIndex)
public int offsetByCodePoints(int index, int codePointOffset)
public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
dstbegin + (srcEnd-srcBegin) - 1
public void setCharAt(int index, char ch)
The index argument must be greater than or equal to 0, and less than the length of this sequence.
public StringBuffer append(Object obj)
The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.
public StringBuffer append(String str)
The characters of the String argument are appended, in order, increasing the length of this sequence by the length of the argument. If str is null, then the four characters "null" are appended.
Let n be the length of this character sequence just prior to execution of the append method. Then the character at index k in the new character sequence is equal to the character at index k in the old character sequence, if k is less than n ; otherwise, it is equal to the character at index k-n in the argument str.
public StringBuffer append(StringBuffer sb)
The characters of the StringBuffer argument are appended, in order, to the contents of this StringBuffer , increasing the length of this StringBuffer by the length of the argument. If sb is null , then the four characters "null" are appended to this StringBuffer .
Let n be the length of the old character sequence, the one contained in the StringBuffer just prior to execution of the append method. Then the character at index k in the new character sequence is equal to the character at index k in the old character sequence, if k is less than n ; otherwise, it is equal to the character at index k-n in the argument sb.
This method synchronizes on this (the destination) object but does not synchronize on the source (sb).
public StringBuffer append(CharSequence s)
The characters of the CharSequence argument are appended, in order, increasing the length of this sequence by the length of the argument.
The result of this method is exactly the same as if it were an invocation of this.append(s, 0, s.length());
This method synchronizes on this (the destination) object but does not synchronize on the source (s).
If s is null, then the four characters "null" are appended.
public StringBuffer append(CharSequence s, int start, int end)
Characters of the argument s, starting at index start, are appended, in order, to the contents of this sequence up to the (exclusive) index end. The length of this sequence is increased by the value of end - start.
Let
n
be the length of this character sequence just prior to execution of the append method. Then the character at index
k
in this character sequence becomes equal to the character at index
k
in
this sequence,
s,
if
k
is less than
n
; otherwise, it is equal to the character at index
k+start-n
in the argument s.
If s is null, then this method appends characters as if the s parameter was a sequence containing the four characters "null".
public StringBuffer append(char[] str)
The characters of the array argument are appended, in order, to the contents of this sequence. The length of this sequence increases by the length of the argument.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char[]) and the characters of that string were then appended to this character sequence.
public StringBuffer append(char[] str, int offset, int len)
Characters of the char array str, starting at index offset, are appended, in order, to the contents of this sequence. The length of this sequence increases by the value of len.
The overall effect is exactly as if the arguments were converted to a string by the method String.valueOf(char[],int,int) and the characters of that string were then appended to this character sequence.
public StringBuffer append(boolean b)
The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.
public StringBuffer append(char c)
The argument is appended to the contents of this sequence. The length of this sequence increases by 1.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char) and the character in that string were then appended to this character sequence.
public StringBuffer append(int i)
The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.
public StringBuffer appendCodePoint(int codePoint)
The argument is appended to the contents of this sequence. The length of this sequence increases by Character.charCount(codePoint) .
The overall effect is exactly as if the argument were converted to a char array by the method Character.toChars(int) and the character in that array were then appended to this character sequence.
public StringBuffer append(long lng)
The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.
public StringBuffer append(float f)
The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this string sequence.
public StringBuffer append(double d)
The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.
public StringBuffer delete(int start, int end)
public StringBuffer deleteCharAt(int index)
Note: If the character at the given index is a supplementary character, this method does not remove the entire character. If correct handling of supplementary characters is required, determine the number of chars to remove by calling Character.charCount(thisSequence.codePointAt(index)), where thisSequence is this sequence.
public StringBuffer replace(int start, int end, String str)
public String substring(int start)
public CharSequence subSequence(int start, int end)
An invocation of this method of the form
behaves in exactly the same way as the invocationsb.subSequence(begin, end)
This method is provided so that this class can implement the CharSequence interface.sb.substring(begin, end)
public String substring(int start, int end)
public StringBuffer insert(int index, char[] str, int offset, int len)
public StringBuffer insert(int offset, Object obj)
The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this sequence at the indicated offset.
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public StringBuffer insert(int offset, String str)
The characters of the String argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument. If str is null, then the four characters "null" are inserted into this sequence.
The character at index k in the new character sequence is equal to:
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public StringBuffer insert(int offset, char[] str)
The characters of the array argument are inserted into the contents of this sequence at the position indicated by offset. The length of this sequence increases by the length of the argument.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char[]) and the characters of that string were then inserted into this character sequence at the position indicated by offset.
public StringBuffer insert(int dstOffset, CharSequence s)
The characters of the CharSequence argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument s.
The result of this method is exactly the same as if it were an invocation of this object's insert(dstOffset, s, 0, s.length()) method.
If s is null, then the four characters "null" are inserted into this sequence.
public StringBuffer insert(int dstOffset, CharSequence s, int start, int end)
The subsequence of the argument s specified by start and end are inserted, in order, into this sequence at the specified destination offset, moving up any characters originally above that position. The length of this sequence is increased by end - start.
The character at index k in this sequence becomes equal to:
The dstOffset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
The start argument must be nonnegative, and not greater than end.
The end argument must be greater than or equal to start, and less than or equal to the length of s.
If s is null, then this method inserts characters as if the s parameter was a sequence containing the four characters "null".
public StringBuffer insert(int offset, boolean b)
The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this sequence at the indicated offset.
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public StringBuffer insert(int offset, char c)
The second argument is inserted into the contents of this sequence at the position indicated by offset. The length of this sequence increases by one.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char) and the character in that string were then inserted into this character sequence at the position indicated by offset.
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public StringBuffer insert(int offset, int i)
The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this sequence at the indicated offset.
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public StringBuffer insert(int offset, long l)
The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this sequence at the position indicated by offset.
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public StringBuffer insert(int offset, float f)
The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this sequence at the indicated offset.
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public StringBuffer insert(int offset, double d)
The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this sequence at the indicated offset.
The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
public int indexOf(String str)
is true.this.toString().startsWith(str, k)
public int indexOf(String str, int fromIndex)
If no such value of k exists, then -1 is returned.k >= Math.min(fromIndex, str.length()) && this.toString().startsWith(str, k)
public int lastIndexOf(String str)
is true.this.toString().startsWith(str, k)
public int lastIndexOf(String str, int fromIndex)
If no such value of k exists, then -1 is returned.k <= Math.min(fromIndex, str.length()) && this.toString().startsWith(str, k)
public StringBuffer reverse()
Note that the reverse operation may result in producing surrogate pairs that were unpaired low-surrogates and high-surrogates before the operation. For example, reversing "\uDC00\uD800" produces "\uD800\uDC00" which is a valid surrogate pair.
public String toString()