java.lang
Class StringBuffer

java.lang.Object
  |
  +--java.lang.StringBuffer

public final class StringBuffer

extends Object

This Class is a growable buffer for characters. It is mainly used to create Strings. The compiler uses it to implement the "+" operator. For example:

	"a" + 4 + "c"
 

is compiled to:

	new StringBuffer().append("a").append(4).append("c").toString()
 

Note that the method toString() does not create a copy of the internal buffer. Instead the buffer is marked as shared. Any further changes to the buffer will cause a copy to be made.

See Also:

String, ByteArrayOutputStream

Constructor Summary

StringBuffer()
Constructs an empty String buffer.

StringBuffer(int length)
Constructs an empty String buffer with the specified initial length.

StringBuffer(String str)
Constructs a String buffer with the specified initial value.

Method Summary

StringBuffer	append(boolean b) Appends a boolean to the end of this buffer.
StringBuffer	append(char c) Appends a character to the end of this buffer.
StringBuffer	append(char[] str) Appends an array of characters to the end of this buffer.
StringBuffer	append(char[] str, int offset, int len) Appends a part of an array of characters to the end of this buffer.
StringBuffer	append(double d) Appends a double to the end of this buffer.
StringBuffer	append(float f) Appends a float to the end of this buffer.
StringBuffer	append(int i) Appends an integer to the end of this buffer.
StringBuffer	append(long l) Appends a long to the end of this buffer.
StringBuffer	append(Object obj) Appends an object to the end of this buffer.
StringBuffer	append(String str) Appends a String to the end of this buffer.
int	capacity() Returns the current capacity of the String buffer.
char	charAt(int index) Returns the character at the specified index.
void	ensureCapacity(int minimumCapacity) Ensures that the capacity of the buffer is at least equal to the specified minimum.
void	getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) Copies the characters of the specified substring (determined by srcBegin and srcEnd) into the character array, starting at the array's dstBegin location.
StringBuffer	insert(int offset, boolean b) Inserts a boolean into the String buffer.
StringBuffer	insert(int offset, char c) Inserts a character into the String buffer.
StringBuffer	insert(int offset, char[] str) Inserts an array of characters into the String buffer.
StringBuffer	insert(int offset, double d) Inserts a double into the String buffer.
StringBuffer	insert(int offset, float f) Inserts a float into the String buffer.
StringBuffer	insert(int offset, int i) Inserts an integer into the String buffer.
StringBuffer	insert(int offset, long l) Inserts a long into the String buffer.
StringBuffer	insert(int offset, Object obj) Inserts an object into the String buffer.
StringBuffer	insert(int offset, String str) Inserts a String into the String buffer.
int	length() Returns the length (character count) of the buffer.
StringBuffer	reverse() Reverse the order of the characters in the String buffer.
void	setCharAt(int index, char ch) Changes the character at the specified index to be ch.
void	setLength(int newLength) Sets the length of the String.
String	toString() Converts to a String representing the data in the buffer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

StringBuffer

public StringBuffer()

Constructs an empty String buffer.

StringBuffer

public StringBuffer(int length)

Constructs an empty String buffer with the specified initial length.

Parameters:

length - the initial length

StringBuffer

public StringBuffer(String str)

Constructs a String buffer with the specified initial value.

Parameters:

str - the initial value of the buffer

Method Detail

length

public int length()

Returns the length (character count) of the buffer.

capacity

public int capacity()

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

ensureCapacity

public void ensureCapacity(int minimumCapacity)

Ensures that the capacity of the buffer is at least equal to the specified minimum.

Parameters:

minimumCapacity - the minimum desired capacity

setLength

public void setLength(int newLength)

Sets the length of the String. If the length is reduced, characters are lost. If the length is extended, the values of the new characters are set to 0.

Parameters:

newLength - the new length of the buffer

Throws:

StringIndexOutOfBoundsException - If the length is invalid.

charAt

public char charAt(int index)

Returns the character at the specified index. An index ranges from 0..length()-1.

Parameters:

index - the index of the desired character

Throws:

StringIndexOutOfBoundsException - If the index is invalid.

getChars

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

Copies the characters of the specified substring (determined by srcBegin and srcEnd) into the character array, starting at the array's dstBegin location. Both srcBegin and srcEnd must be legal indexes into the buffer.

Parameters:

srcBegin - begin copy at this offset in the String

srcEnd - stop copying at this offset in the String

dst - the array to copy the data into

dstBegin - offset into dst

Throws:

StringIndexOutOfBoundsException - If there is an invalid index into the buffer.

setCharAt

public void setCharAt(int index,
                      char ch)

Changes the character at the specified index to be ch.

Parameters:

index - the index of the character

ch - the new character

Throws:

StringIndexOutOfBoundsException - If the index is invalid.

append

public StringBuffer append(Object obj)

Appends an object to the end of this buffer.

Parameters:

obj - the object to be appended

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(String str)

Appends a String to the end of this buffer.

Parameters:

str - the String to be appended

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(char[] str)

Appends an array of characters to the end of this buffer.

Parameters:

str - the characters to be appended

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(char[] str,
                           int offset,
                           int len)

Appends a part of an array of characters to the end of this buffer.

Parameters:

str - the characters to be appended

offset - where to start

len - the number of characters to add

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(boolean b)

Appends a boolean to the end of this buffer.

Parameters:

b - the boolean to be appended

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(char c)

Appends a character to the end of this buffer.

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(int i)

Appends an integer to the end of this buffer.

Parameters:

i - the integer to be appended

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(long l)

Appends a long to the end of this buffer.

Parameters:

l - the long to be appended

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(float f)

Appends a float to the end of this buffer.

Parameters:

f - the float to be appended

Returns:

the StringBuffer itself, NOT a new one.

append

public StringBuffer append(double d)

Appends a double to the end of this buffer.

Parameters:

d - the double to be appended

Returns:

the StringBuffer itself, NOT a new one.

insert

public StringBuffer insert(int offset,
                           Object obj)

Inserts an object into the String buffer.

Parameters:

offset - the offset at which to insert

obj - the object to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

insert

public StringBuffer insert(int offset,
                           String str)

Inserts a String into the String buffer.

Parameters:

offset - the offset at which to insert

str - the String to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

insert

public StringBuffer insert(int offset,
                           char[] str)

Inserts an array of characters into the String buffer.

Parameters:

offset - the offset at which to insert

str - the characters to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

insert

public StringBuffer insert(int offset,
                           boolean b)

Inserts a boolean into the String buffer.

Parameters:

offset - the offset at which to insert

b - the boolean to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

insert

public StringBuffer insert(int offset,
                           char c)

Inserts a character into the String buffer.

Parameters:

offset - the offset at which to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset invalid.

insert

public StringBuffer insert(int offset,
                           int i)

Inserts an integer into the String buffer.

Parameters:

offset - the offset at which to insert

i - the integer to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

insert

public StringBuffer insert(int offset,
                           long l)

Inserts a long into the String buffer.

Parameters:

offset - the offset at which to insert

l - the long to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

insert

public StringBuffer insert(int offset,
                           float f)

Inserts a float into the String buffer.

Parameters:

offset - the offset at which to insert

f - the float to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

insert

public StringBuffer insert(int offset,
                           double d)

Inserts a double into the String buffer.

Parameters:

offset - the offset at which to insert

d - the double to insert

Returns:

the StringBuffer itself, NOT a new one.

Throws:

StringIndexOutOfBoundsException - If the offset is invalid.

reverse

public StringBuffer reverse()

Reverse the order of the characters in the String buffer.

toString

public String toString()

Converts to a String representing the data in the buffer.

Overrides:

toString in class Object