StringBuffer

Class StringBuffer

public final class StringBuffer extends AbstractStringBuilder implements Serializable, CharSequence

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).

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 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.

Since: JDK1.0

Version: 1.89, 07/11/03

Author: Arthur van Hoff

See Also: java.lang.StringBuilder String

Constructor Summary
	StringBuffer() Constructs a string buffer with no characters in it and an initial capacity of 16 characters.
	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.
	StringBuffer(CharSequence seq) Constructs a string buffer that contains the same characters as the specified `CharSequence`.

Constructor Summary

StringBuffer()

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

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.

StringBuffer(CharSequence seq)

Constructs a string buffer that contains the same characters as the specified CharSequence.

Method Summary
StringBuffer	append(Object obj)
StringBuffer	append(String str)
StringBuffer	append(StringBuffer sb) Appends the specified `StringBuffer` to this sequence.
StringBuffer	append(CharSequence s) Appends the specified `CharSequence` to this sequence.
StringBuffer	append(CharSequence s, int srcOffset, int len) Appends a subsequence of the specified `CharSequence` to this sequence.
StringBuffer	append(char[] str)
StringBuffer	append(char[] str, int offset, int len)
StringBuffer	append(boolean b)
StringBuffer	append(char c)
StringBuffer	append(int i)
StringBuffer	append(long lng)
StringBuffer	append(float f)
StringBuffer	append(double d)
int	capacity()
char	charAt(int index)
StringBuffer	delete(int start, int end)
StringBuffer	deleteCharAt(int index)
void	ensureCapacity(int minimumCapacity)
void	getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
int	indexOf(String str)
int	indexOf(String str, int fromIndex)
StringBuffer	insert(int index, char[] str, int offset, int len)
StringBuffer	insert(int offset, Object obj)
StringBuffer	insert(int offset, String str)
StringBuffer	insert(int offset, char[] str)
StringBuffer	insert(int dstOffset, CharSequence s)
StringBuffer	insert(int dstOffset, CharSequence s, int srcOffset, int len)
StringBuffer	insert(int offset, boolean b)
StringBuffer	insert(int offset, char c)
StringBuffer	insert(int offset, int i)
StringBuffer	insert(int offset, long l)
StringBuffer	insert(int offset, float f)
StringBuffer	insert(int offset, double d)
int	lastIndexOf(String str)
int	lastIndexOf(String str, int fromIndex)
int	length()
StringBuffer	replace(int start, int end, String str)
StringBuffer	reverse()
void	setCharAt(int index, char ch)
void	setLength(int newLength)
CharSequence	subSequence(int start, int end)
String	substring(int start)
String	substring(int start, int end)
String	toString()
void	trimToSize()