StringBuffer

Athread-safe(线程安全), mutable sequence of characters. A string buffer（缓冲区） is like aString, but can bemodified（修改）. At any point in time it contains some(某些) particular（特定的） sequence of characters, but the length and content of the sequence can be changed through certain（某些） method calls.

String buffers are safe for use bymultiple threads(多线程). The methods are synchronized(同步) where necessary(必要)so that(所以) all the operations（操作） on any particular(特定) instance behave as(像) if they occur(发生) in someserial(串行的) order（序列） that isconsistent with（一致） the order(顺序) of themethod calls(调用方法) made byeach of the individual(每个独立的) threads involved(涉及的).

Theprincipal(最重要的) operations on aStringBufferare theappendandinsertmethods, which are overloaded（重载） so as to accept data(接受数据) of any type. Each effectively(有效的) converts a given(给定的) datum(数据) to a string and then appends or inserts the characters of that string to the string buffer. Theappendmethod always adds these characters at the end(末端) of the buffer; theinsertmethod adds the characters at a specified point.

For example, ifzrefers(属于) to a string buffer object whose current contents are "start", then the method callz.append("le")would cause the string buffer to contain "startle",whereas(反之)z.insert(4, "le")would alter the string buffer to contain "starlet".

In general(情况下), if sb refers to an instance of aStringBuffer, thensb.append(x)has the same effect(效果) assb.insert(sb.length(), x).

Whenever an operationoccurs involving(有关的) a source sequence (such as appending or inserting from a source sequence) this class synchronizes(同步) only on the string buffer performing(执行) the operation, not on the source.

Every string buffer has a capacity(容量). As long as the length of the character sequence contained in the string buffer does not exceed(超过) the capacity, it is not necessary toallocate(分配)a newinternal(内部) buffer array. If the internal buffer overflows(溢出), it isautomatically(自动的)made larger(增大). As of release(发布) JDK 5, this class has been supplemented(增加) with anequivalent class(等价类) designed for use by a single thread,StringBuilder. TheStringBuilderclass shouldgenerally(一般) be used in preference(优先) to this one, as it supports all of the same operations but it is faster(更快的), as it performs(执行) no synchronization.

Since:

JDK1.0

See Also:

StringBuilder, String, Serialized Form

Constructor Summary
`StringBuffer()` Constructs a string buffer with no characters in it and an initial capacity of 16 characters.
`StringBuffer(CharSequenceseq)` 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(Stringstr)` Constructs a string buffer initialized to the contents of the specified string.

Method Summary
`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(CharSequences)` Appends the specified`CharSequence`to this sequence.
`StringBuffer`	`append(CharSequences, 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(Objectobj)` Appends the string representation of the`Object`argument.
`StringBuffer`	`append(Stringstr)` Appends the specified string to this character sequence.
`StringBuffer`	`append(StringBuffersb)` 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(Stringstr)` Returns the index within this string of the first occurrence of the specified substring.
`int`	`indexOf(Stringstr, 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,CharSequences)` Inserts the specified`CharSequence`into this sequence.
`StringBuffer`	`insert(int dstOffset,CharSequences, 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,Objectobj)` Inserts the string representation of the`Object`argument into this character sequence.
`StringBuffer`	`insert(int offset,Stringstr)` Inserts the string into this character sequence.
`int`	`lastIndexOf(Stringstr)` Returns the index within this string of the rightmost occurrence of the specified substring.
`int`	`lastIndexOf(Stringstr, 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,Stringstr)` 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
`clone,equals,finalize,getClass,hashCode,notify,notifyAll,wait,wait,wait`

Constructor Detail

StringBuffer

publicStringBuffer()

Constructs a string buffer with no characters in it and an initial capacity of 16 characters.

StringBuffer

publicStringBuffer(int capacity)

Constructs a string buffer with no characters in it and the specified initial capacity.

Parameters:

capacity- the initial capacity.

Throws:

NegativeArraySizeException- if the capacityargument is less than 0.

StringBuffer

publicStringBuffer(Stringstr)

Constructs a string buffer initialized to the contents of the specified string. The initial capacity of the string buffer is 16plus the length of the string argument.

Parameters:

str- the initial contents of the buffer.

Throws:

NullPointerException- if stris null

StringBuffer

publicStringBuffer(CharSequenceseq)

Constructs a string buffer that contains the same characters as the specified CharSequence. The initial capacity of the string buffer is 16plus the length of the CharSequenceargument.

If the length of the specifiedCharSequenceis less than or equal to zero, then an empty buffer of capacity16is returned.

Parameters:

seq- the sequence to copy.

Throws:

NullPointerException- if seqis null

Since:

1.5

Method Detail

length

public intlength()

Returns the length (character count).

Specified by:

lengthin interface CharSequence

Returns:

the length of the sequence of characters currently represented by this object

capacity

public intcapacity()

Returns the current capacity. The capacity is the amount of storage available for newly inserted characters, beyond which an allocation will occur.

Returns:

the current capacity

ensureCapacity

public voidensureCapacity(int minimumCapacity)

Ensures that the capacity is at least equal to the specified minimum. If the current capacity is less than the argument, then a new internal array is allocated with greater capacity. The new capacity is the larger of:

TheminimumCapacityargument.
Twice the old capacity, plus2.

If the minimumCapacityargument is nonpositive, this method takes no action and simply returns.

Parameters:

minimumCapacity- the minimum desired capacity.

trimToSize

public voidtrimToSize()

Attempts to reduce storage used for the character sequence. If the buffer is larger than necessary to hold its current sequence of characters, then it may be resized to become more space efficient. Calling this method may, but is not required to, affect the value returned by a subsequent call to the capacity()method.

Since:

1.5

setLength

public voidsetLength(int newLength)

Sets the length of the character sequence. The sequence is changed to a new character sequence whose length is specified by the argument. For every nonnegative index kless than newLength, the character at index kin the new character sequence is the same as the character at index kin the old sequence if kis less than the length of the old character sequence; otherwise, it is the null character '\u0000'. In other words, if the newLengthargument is less than the current length, the length is changed to the specified length.

If thenewLengthargument is greater than or equal to the current length, sufficient null characters ('\u0000') are appended so that length becomes thenewLengthargument.

ThenewLengthargument must be greater than or equal to0.

Parameters:

newLength- the new length

Throws:

IndexOutOfBoundsException- if the newLengthargument is negative.

See Also:

length()

charAt

public charcharAt(int index)

Returns the charvalue in this sequence at the specified index. The first charvalue is at index 0, the next at index 1, and so on, as in array indexing.

The index argument must be greater than or equal to0, and less than the length of this sequence.

If thecharvalue specified by the index is asurrogate, the surrogate value is returned.

Specified by:

charAtin interface CharSequence

Parameters:

index- the index of the desired charvalue.

Returns:

the charvalue at the specified index.

Throws:

IndexOutOfBoundsException- if indexis negative or greater than or equal to length().

See Also:

length()

codePointAt

public intcodePointAt(int index)

Returns the character (Unicode code point) at the specified index. The index refers to charvalues (Unicode code units) and ranges from 0to length() - 1.

If thecharvalue specified at the given index is in the high-surrogate range, the following index is less than the length of this sequence, and thecharvalue at the following index is in the low-surrogate range, then the supplementary code point corresponding to this surrogate pair is returned. Otherwise, thecharvalue at the given index is returned.

Parameters:

index- the index to the charvalues

Returns:

the code point value of the character at the index

Since:

1.5

codePointBefore

public intcodePointBefore(int index)

Returns the character (Unicode code point) before the specified index. The index refers to charvalues (Unicode code units) and ranges from 1to length().

If thecharvalue at(index - 1)is in the low-surrogate range,(index - 2)is not negative, and thecharvalue at(index - 2)is in the high-surrogate range, then the supplementary code point value of the surrogate pair is returned. If thecharvalue atindex - 1is an unpaired low-surrogate or a high-surrogate, the surrogate value is returned.

Parameters:

index- the index following the code point that should be returned

Returns:

the Unicode code point value before the given index.

Since:

1.5

codePointCount

public intcodePointCount(int beginIndex, int endIndex)

Returns the number of Unicode code points in the specified text range of this sequence. The text range begins at the specified beginIndexand extends to the charat index endIndex - 1. Thus the length (in chars) of the text range is endIndex-beginIndex. Unpaired surrogates within this sequence count as one code point each.

Parameters:

beginIndex- the index to the first charof the text range.

endIndex- the index after the last charof the text range.

Returns:

the number of Unicode code points in the specified text range

Since:

1.5

offsetByCodePoints

public intoffsetByCodePoints(int index, int codePointOffset)

Returns the index within this sequence that is offset from the given indexby codePointOffsetcode points. Unpaired surrogates within the text range given by indexand codePointOffsetcount as one code point each.

Parameters:

index- the index to be offset

codePointOffset- the offset in code points

Returns:

the index within this sequence

Since:

1.5

getChars

public voidgetChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)

Characters are copied from this sequence into the destination character array dst. The first character to be copied is at index srcBegin; the last character to be copied is at index srcEnd-1. The total number of characters to be copied is srcEnd-srcBegin. The characters are copied into the subarray of dststarting at index dstBeginand ending at index:

dstbegin + (srcEnd-srcBegin) - 1

Parameters:

srcBegin- start copying at this offset.

srcEnd- stop copying at this offset.

dst- the array to copy the data into.

dstBegin- offset into dst.

Throws:

NullPointerException- if dstis null.

IndexOutOfBoundsException- if any of the following is true:

srcBeginis negative
dstBeginis negative
thesrcBeginargument is greater than thesrcEndargument.
srcEndis greater thanthis.length().
dstBegin+srcEnd-srcBeginis greater thandst.length

setCharAt

public voidsetCharAt(int index, char ch)

The character at the specified index is set to ch. This sequence is altered to represent a new character sequence that is identical to the old character sequence, except that it contains the character chat position index.

The index argument must be greater than or equal to0, and less than the length of this sequence.

Parameters:

index- the index of the character to modify.

ch- the new character.

Throws:

IndexOutOfBoundsException- if indexis negative or greater than or equal to length().

See Also:

length()

append

publicStringBufferappend(Objectobj)

Appends the string representation of the Objectargument.

The argument is converted to a string as if by the methodString.valueOf, and the characters of that string are then appended to this sequence.

Parameters:

obj- an Object.

Returns:

a reference to this object.

append

publicStringBufferappend(Stringstr)

Appends the specified string to this character sequence.

The characters of theStringargument are appended, in order, increasing the length of this sequence by the length of the argument. Ifstrisnull, then the four characters"null"are appended.

Letnbe the length of this character sequence just prior to execution of theappendmethod. Then the character at indexkin the new character sequence is equal to the character at indexkin the old character sequence, ifkis less thann; otherwise, it is equal to the character at indexk-nin the argumentstr.

Parameters:

str- a string.

Returns:

a reference to this object.

append

publicStringBufferappend(StringBuffersb)

Appends the specified StringBufferto this sequence.

The characters of theStringBufferargument are appended, in order, to the contents of thisStringBuffer, increasing the length of thisStringBufferby the length of the argument. Ifsbisnull, then the four characters"null"are appended to thisStringBuffer.

Letnbe the length of the old character sequence, the one contained in theStringBufferjust prior to execution of theappendmethod. Then the character at indexkin the new character sequence is equal to the character at indexkin the old character sequence, ifkis less thann; otherwise, it is equal to the character at indexk-nin the argumentsb.

This method synchronizes onthis(the destination) object but does not synchronize on the source (sb).

Parameters:

sb- the StringBufferto append.

Returns:

a reference to this object.

Since:

1.4

append

publicStringBufferappend(CharSequences)

Appends the specified CharSequenceto this sequence.

The characters of theCharSequenceargument 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).

Ifsisnull, then the four characters"null"are appended.

Specified by:

appendin interface Appendable

Parameters:

s- the CharSequenceto append.

Returns:

a reference to this object.

Since:

1.5

append

publicStringBufferappend(CharSequences, int start, int end)

Appends a subsequence of the specified CharSequenceto this sequence.

Characters of the arguments, starting at indexstart, are appended, in order, to the contents of this sequence up to the (exclusive) indexend. The length of this sequence is increased by the value ofend - start.

Letnbe the length of this character sequence just prior to execution of theappendmethod. Then the character at indexkin this character sequence becomes equal to the character at indexkin this sequence, ifkis less thann; otherwise, it is equal to the character at indexk+start-nin the arguments.

Ifsisnull, then this method appends characters as if the s parameter was a sequence containing the four characters"null".

Specified by:

appendin interface Appendable

Parameters:

s- the sequence to append.

start- the starting index of the subsequence to be appended.

end- the end index of the subsequence to be appended.

Returns:

a reference to this object.

Throws:

IndexOutOfBoundsException- if startor endare negative, or startis greater than endor endis greater than s.length()

Since:

1.5

append

publicStringBufferappend(char[] str)

Appends the string representation of the chararray argument to this sequence.

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 methodString.valueOf(char[])and the characters of that string were thenappendedto this character sequence.

Parameters:

str- the characters to be appended.

Returns:

a reference to this object.

append

publicStringBufferappend(char[] str, int offset, int len)

Appends the string representation of a subarray of the chararray argument to this sequence.

Characters of thechararraystr, starting at indexoffset, are appended, in order, to the contents of this sequence. The length of this sequence increases by the value oflen.

The overall effect is exactly as if the arguments were converted to a string by the methodString.valueOf(char[],int,int)and the characters of that string were thenappendedto this character sequence.

Parameters:

str- the characters to be appended.

offset- the index of the first charto append.

len- the number of chars to append.

Returns:

a reference to this object.

append

publicStringBufferappend(boolean b)

Appends the string representation of the booleanargument to the sequence.

The argument is converted to a string as if by the methodString.valueOf, and the characters of that string are then appended to this sequence.

Parameters:

b- a boolean.

Returns:

a reference to this object.

See Also:

String.valueOf(boolean), append(java.lang.String)

append

publicStringBufferappend(char c)

Appends the string representation of the charargument to this sequence.

The argument is appended to the contents of this sequence. The length of this sequence increases by1.

The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(char)and the character in that string were thenappendedto this character sequence.

Specified by:

appendin interface Appendable

Parameters:

c- a char.

Returns:

a reference to this object.

append

publicStringBufferappend(int i)

Appends the string representation of the intargument to this sequence.

The argument is converted to a string as if by the methodString.valueOf, and the characters of that string are then appended to this sequence.

Parameters:

i- an int.

Returns:

a reference to this object.

See Also:

String.valueOf(int), append(java.lang.String)

appendCodePoint

publicStringBufferappendCodePoint(int codePoint)

Appends the string representation of the codePointargument to this sequence.

The argument is appended to the contents of this sequence. The length of this sequence increases byCharacter.charCount(codePoint).

The overall effect is exactly as if the argument were converted to achararray by the methodCharacter.toChars(int)and the character in that array were thenappendedto this character sequence.

Parameters:

codePoint- a Unicode code point

Returns:

a reference to this object.

Since:

1.5

append

publicStringBufferappend(long lng)

Appends the string representation of the longargument to this sequence.

The argument is converted to a string as if by the methodString.valueOf, and the characters of that string are then appended to this sequence.

Parameters:

lng- a long.

Returns:

a reference to this object.

See Also:

String.valueOf(long), append(java.lang.String)

append

publicStringBufferappend(float f)

Appends the string representation of the floatargument to this sequence.

The argument is converted to a string as if by the methodString.valueOf, and the characters of that string are then appended to this string sequence.

Parameters:

f- a float.

Returns:

a reference to this object.

See Also:

String.valueOf(float), append(java.lang.String)

append

publicStringBufferappend(double d)

Appends the string representation of the doubleargument to this sequence.

The argument is converted to a string as if by the methodString.valueOf, and the characters of that string are then appended to this sequence.

Parameters:

d- a double.

Returns:

a reference to this object.

See Also:

String.valueOf(double), append(java.lang.String)

delete

publicStringBufferdelete(int start, int end)

Removes the characters in a substring of this sequence. The substring begins at the specified startand extends to the character at index end - 1or to the end of the sequence if no such character exists. If startis equal to end, no changes are made.

Parameters:

start- The beginning index, inclusive.

end- The ending index, exclusive.

Returns:

This object.

Throws:

StringIndexOutOfBoundsException- if startis negative, greater than length(), or greater than end.

Since:

1.2

deleteCharAt

publicStringBufferdeleteCharAt(int index)

Removes the charat the specified position in this sequence. This sequence is shortened by one char.

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 ofchars to remove by callingCharacter.charCount(thisSequence.codePointAt(index)), wherethisSequenceis this sequence.

Parameters:

index- Index of charto remove

Returns:

This object.

Throws:

StringIndexOutOfBoundsException- if the indexis negative or greater than or equal to length().

Since:

1.2

replace

publicStringBufferreplace(int start, int end,Stringstr)

Replaces the characters in a substring of this sequence with characters in the specified String. The substring begins at the specified startand extends to the character at index end - 1or to the end of the sequence if no such character exists. First the characters in the substring are removed and then the specified Stringis inserted at start. (This sequence will be lengthened to accommodate the specified String if necessary.)

Parameters:

start- The beginning index, inclusive.

end- The ending index, exclusive.

str- String that will replace previous contents.

Returns:

This object.

Throws:

StringIndexOutOfBoundsException- if startis negative, greater than length(), or greater than end.

Since:

1.2

substring

publicStringsubstring(int start)

Returns a new Stringthat contains a subsequence of characters currently contained in this character sequence. The substring begins at the specified index and extends to the end of this sequence.

Parameters:

start- The beginning index, inclusive.

Returns:

The new string.

Throws:

StringIndexOutOfBoundsException- if startis less than zero, or greater than the length of this object.

Since:

1.2

subSequence

publicCharSequencesubSequence(int start, int end)

Returns a new character sequence that is a subsequence of this sequence.

An invocation of this method of the form

sb.subSequence(begin, end)

behaves in exactly the same way as the invocation

sb.substring(begin, end)

This method is provided so that this class can implement the CharSequenceinterface.

Specified by:

subSequencein interface CharSequence

Parameters:

start- the start index, inclusive.

end- the end index, exclusive.

Returns:

the specified subsequence.

Throws:

IndexOutOfBoundsException- if startor endare negative, if endis greater than length(), or if startis greater than end

Since:

1.4

substring

publicStringsubstring(int start, int end)

Returns a new Stringthat contains a subsequence of characters currently contained in this sequence. The substring begins at the specified startand extends to the character at index end - 1.

Parameters:

start- The beginning index, inclusive.

end- The ending index, exclusive.

Returns:

The new string.

Throws:

StringIndexOutOfBoundsException- if startor endare negative or greater than length(), or startis greater than end.

Since:

1.2

insert

publicStringBufferinsert(int index, char[] str, int offset, int len)

Inserts the string representation of a subarray of the strarray argument into this sequence. The subarray begins at the specified offsetand extends len chars. The characters of the subarray are inserted into this sequence at the position indicated by index. The length of this sequence increases by len chars.

Parameters:

index- position at which to insert subarray.

str- A chararray.

offset- the index of the first charin subarray to be inserted.

len- the number of chars in the subarray to be inserted.

Returns:

This object

Throws:

StringIndexOutOfBoundsException- if indexis negative or greater than length(), or offsetor lenare negative, or (offset+len)is greater than str.length.

Since:

1.2

insert

publicStringBufferinsert(int offset,Objectobj)

Inserts the string representation of the Objectargument into this character sequence.

The second argument is converted to a string as if by the methodString.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 to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

obj- an Object.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

insert

publicStringBufferinsert(int offset,Stringstr)

Inserts the string into this character sequence.

The characters of theStringargument 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. Ifstrisnull, then the four characters"null"are inserted into this sequence.

The character at indexkin the new character sequence is equal to:

the character at indexkin the old character sequence, ifkis less thanoffset
the character at indexk-offsetin the argumentstr, ifkis not less thanoffsetbut is less thanoffset+str.length()
the character at indexk-str.length()in the old character sequence, ifkis not less thanoffset+str.length()

The offset argument must be greater than or equal to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

str- a string.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

See Also:

length()

insert

publicStringBufferinsert(int offset, char[] str)

Inserts the string representation of the chararray argument into this sequence.

The characters of the array argument are inserted into the contents of this sequence at the position indicated byoffset. 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 methodString.valueOf(char[])and the characters of that string were theninsertedinto this character sequence at the position indicated byoffset.

Parameters:

offset- the offset.

str- a character array.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

insert

publicStringBufferinsert(int dstOffset,CharSequences)

Inserts the specified CharSequenceinto this sequence.

The characters of theCharSequenceargument 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.

Ifsisnull, then the four characters"null"are inserted into this sequence.

Parameters:

dstOffset- the offset.

s- the sequence to be inserted

Returns:

a reference to this object.

Throws:

IndexOutOfBoundsException- if the offset is invalid.

Since:

1.5

insert

publicStringBufferinsert(int dstOffset,CharSequences, int start, int end)

Inserts a subsequence of the specified CharSequenceinto this sequence.

The subsequence of the argumentsspecified bystartandendare 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 byend - start.

The character at indexkin this sequence becomes equal to:

the character at indexkin this sequence, ifkis less thandstOffset
the character at indexk+start-dstOffsetin the arguments, ifkis greater than or equal todstOffsetbut is less thandstOffset+end-start
the character at indexk-(end-start)in this sequence, ifkis greater than or equal todstOffset+end-start

The dstOffset argument must be greater than or equal to0, and less than or equal to the length of this sequence.

The start argument must be nonnegative, and not greater thanend.

The end argument must be greater than or equal tostart, and less than or equal to the length of s.

Ifsisnull, then this method inserts characters as if the s parameter was a sequence containing the four characters"null".

Parameters:

dstOffset- the offset in this sequence.

s- the sequence to be inserted.

start- the starting index of the subsequence to be inserted.

end- the end index of the subsequence to be inserted.

Returns:

a reference to this object.

Throws:

IndexOutOfBoundsException- if dstOffsetis negative or greater than this.length(), or startor endare negative, or startis greater than endor endis greater than s.length()

Since:

1.5

insert

publicStringBufferinsert(int offset, boolean b)

Inserts the string representation of the booleanargument into this sequence.

The second argument is converted to a string as if by the methodString.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 to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

b- a boolean.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

See Also:

String.valueOf(boolean), insert(int, java.lang.String), length()

insert

publicStringBufferinsert(int offset, char c)

Inserts the string representation of the charargument into this sequence.

The second argument is inserted into the contents of this sequence at the position indicated byoffset. The length of this sequence increases by one.

The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(char)and the character in that string were theninsertedinto this character sequence at the position indicated byoffset.

The offset argument must be greater than or equal to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

c- a char.

Returns:

a reference to this object.

Throws:

IndexOutOfBoundsException- if the offset is invalid.

See Also:

length()

insert

publicStringBufferinsert(int offset, int i)

Inserts the string representation of the second intargument into this sequence.

The second argument is converted to a string as if by the methodString.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 to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

i- an int.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

See Also:

String.valueOf(int), insert(int, java.lang.String), length()

insert

publicStringBufferinsert(int offset, long l)

Inserts the string representation of the longargument into this sequence.

The second argument is converted to a string as if by the methodString.valueOf, and the characters of that string are then inserted into this sequence at the position indicated byoffset.

The offset argument must be greater than or equal to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

l- a long.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

See Also:

String.valueOf(long), insert(int, java.lang.String), length()

insert

publicStringBufferinsert(int offset, float f)

Inserts the string representation of the floatargument into this sequence.

The second argument is converted to a string as if by the methodString.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 to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

f- a float.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

See Also:

String.valueOf(float), insert(int, java.lang.String), length()

insert

publicStringBufferinsert(int offset, double d)

Inserts the string representation of the doubleargument into this sequence.

The second argument is converted to a string as if by the methodString.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 to0, and less than or equal to the length of this sequence.

Parameters:

offset- the offset.

d- a double.

Returns:

a reference to this object.

Throws:

StringIndexOutOfBoundsException- if the offset is invalid.

See Also:

String.valueOf(double), insert(int, java.lang.String), length()

indexOf

public intindexOf(Stringstr)

Returns the index within this string of the first occurrence of the specified substring. The integer returned is the smallest value ksuch that:

this.toString().startsWith(str,k)

is true.

Parameters:

str- any string.

Returns:

if the string argument occurs as a substring within this object, then the index of the first character of the first such substring is returned; if it does not occur as a substring, -1is returned.

Throws:

NullPointerException- if stris null.

Since:

1.4

indexOf

public intindexOf(Stringstr, int fromIndex)

Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. The integer returned is the smallest value kfor which:

k >= Math.min(fromIndex, str.length()) && this.toString().startsWith(str, k)

If no such value of kexists, then -1 is returned.

Parameters:

str- the substring for which to search.

fromIndex- the index from which to start the search.

Returns:

the index within this string of the first occurrence of the specified substring, starting at the specified index.

Throws:

NullPointerException- if stris null.

Since:

1.4

lastIndexOf

public intlastIndexOf(Stringstr)

Returns the index within this string of the rightmost occurrence of the specified substring. The rightmost empty string "" is considered to occur at the index value this.length(). The returned index is the largest value ksuch that

this.toString().startsWith(str, k)

is true.

Parameters:

str- the substring to search for.

Returns:

if the string argument occurs one or more times as a substring within this object, then the index of the first character of the last such substring is returned. If it does not occur as a substring, -1is returned.

Throws:

NullPointerException- if stris null.

Since:

1.4

lastIndexOf

public intlastIndexOf(Stringstr, int fromIndex)

Returns the index within this string of the last occurrence of the specified substring. The integer returned is the largest value ksuch that:

k <= Math.min(fromIndex,="Math.min(fromIndex," str.length())="str.length())" &&="&&" this.toString().startsWith(str,="this.toString().startsWith(str," k)="k)"

If no such value of kexists, then -1 is returned.

Parameters:

str- the substring to search for.

fromIndex- the index to start the search from.

Returns:

the index within this sequence of the last occurrence of the specified substring.

Throws:

NullPointerException- if stris null.

Since:

1.4

reverse

publicStringBufferreverse()

Causes this character sequence to be replaced by the reverse of the sequence. If there are any surrogate pairs included in the sequence, these are treated as single characters for the reverse operation. Thus, the order of the high-low surrogates is never reversed. Let nbe the character length of this character sequence (not the length in charvalues) just prior to execution of the reversemethod. Then the character at index kin the new character sequence is equal to the character at index n-k-1in the old character sequence.

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.

Returns:

a reference to this object.

Since:

JDK1.0.2

toString

publicStringtoString()

Returns a string representing the data in this sequence. A new Stringobject is allocated and initialized to contain the character sequence currently represented by this object. This Stringis then returned. Subsequent changes to this sequence do not affect the contents of the String.

Specified by:

toStringin interface CharSequence

Returns:

a string representation of this sequence of characters.

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