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java.lang

Class StringBuffer

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

All Implemented Interfaces:

Serializable, CharSequence


public final class StringBuffer

extends Object

implements Serializable, CharSequence

StringBuffer represents a changeable String. It provides the operations required to modify the StringBuffer, including insert, replace, delete, append, and reverse. It is thread-safe; meaning that all modifications to a buffer are in synchronized methods.

StringBuffers 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 StringBuffer 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 StringBuffer operation:
a + b
is the same as
new StringBuffer().append(a).append(b).toString().

Classpath's StringBuffer is capable of sharing memory with Strings for efficiency. This will help when a StringBuffer is converted to a String and the StringBuffer is not changed after that (quite common when performing string concatenation).

Since:Authors:See Also:

Constructor Summary

StringBuffer()

Create a new StringBuffer with default capacity 16.
StringBuffer(int capacity)

Create an empty StringBuffer with the specified initial capacity.
StringBuffer(java.lang.String str)

Create a new StringBuffer with the characters in the specified String.

Method Summary

java.lang.StringBufferappend(java.lang.Object obj)

Append the String value of the argument to this StringBuffer.
synchronized java.lang.StringBufferappend(java.lang.String str)

Append the String to this StringBuffer.
synchronized java.lang.StringBufferappend(java.lang.StringBuffer stringBuffer)

Append the StringBuffer value of the argument to this StringBuffer.
java.lang.StringBufferappend(char[] data)

Append the char array to this StringBuffer.
synchronized java.lang.StringBufferappend(char[] data, int offset, int count)

Append part of the char array to this StringBuffer.
java.lang.StringBufferappend(boolean bool)

Append the String value of the argument to this StringBuffer.
synchronized java.lang.StringBufferappend(char ch)

Append the char to this StringBuffer.
java.lang.StringBufferappend(int inum)

Append the String value of the argument to this StringBuffer.
java.lang.StringBufferappend(long lnum)

Append the String value of the argument to this StringBuffer.
java.lang.StringBufferappend(float fnum)

Append the String value of the argument to this StringBuffer.
java.lang.StringBufferappend(double dnum)

Append the String value of the argument to this StringBuffer.
synchronized intcapacity()

Get the total number of characters this StringBuffer can support before it must be grown.
synchronized charcharAt(int index)

Get the character at the specified index.
synchronized java.lang.StringBufferdelete(int start, int end)

Delete characters from this StringBuffer.
java.lang.StringBufferdeleteCharAt(int index)

Delete a character from this StringBuffer.
synchronized voidensureCapacity(int minimumCapacity)

Increase the capacity of this StringBuffer.
synchronized voidgetChars(int srcOffset, int srcEnd, char[] dst, int dstOffset)

Get the specified array of characters.
intindexOf(java.lang.String str)

Finds the first instance of a substring in this StringBuffer.
synchronized intindexOf(java.lang.String str, int fromIndex)

Finds the first instance of a String in this StringBuffer, starting at a given index.
synchronized java.lang.StringBufferinsert(int offset, char[] str, int str_offset, int len)

Insert a subarray of the char[] argument into this StringBuffer.
java.lang.StringBufferinsert(int offset, java.lang.Object obj)

Insert the String value of the argument into this StringBuffer.
synchronized java.lang.StringBufferinsert(int offset, java.lang.String str)

Insert the String argument into this StringBuffer.
java.lang.StringBufferinsert(int offset, char[] data)

Insert the char[] argument into this StringBuffer.
java.lang.StringBufferinsert(int offset, boolean bool)

Insert the String value of the argument into this StringBuffer.
synchronized java.lang.StringBufferinsert(int offset, char ch)

Insert the char argument into this StringBuffer.
java.lang.StringBufferinsert(int offset, int inum)

Insert the String value of the argument into this StringBuffer.
java.lang.StringBufferinsert(int offset, long lnum)

Insert the String value of the argument into this StringBuffer.
java.lang.StringBufferinsert(int offset, float fnum)

Insert the String value of the argument into this StringBuffer.
java.lang.StringBufferinsert(int offset, double dnum)

Insert the String value of the argument into this StringBuffer.
intlastIndexOf(java.lang.String str)

Finds the last instance of a substring in this StringBuffer.
synchronized intlastIndexOf(java.lang.String str, int fromIndex)

Finds the last instance of a String in this StringBuffer, starting at a given index.
synchronized intlength()

Get the length of the String this StringBuffer would create.
synchronized java.lang.StringBufferreplace(int start, int end, java.lang.String str)

Replace characters between index start (inclusive) and end (exclusive) with str.
synchronized java.lang.StringBufferreverse()

Reverse the characters in this StringBuffer.
synchronized voidsetCharAt(int index, char ch)

Set the character at the specified index.
synchronized voidsetLength(int newLength)

Set the length of this StringBuffer.
java.lang.CharSequencesubSequence(int beginIndex, int endIndex)

Creates a substring of this StringBuffer, starting at a specified index and ending at one character before a specified index.
java.lang.Stringsubstring(int beginIndex)

Creates a substring of this StringBuffer, starting at a specified index and ending at the end of this StringBuffer.
synchronized java.lang.Stringsubstring(int beginIndex, int endIndex)

Creates a substring of this StringBuffer, starting at a specified index and ending at one character before a specified index.
java.lang.StringtoString()

Convert this StringBuffer to a String.

Constructor Details

StringBuffer

public StringBuffer()

Create a new StringBuffer with default capacity 16.


StringBuffer

public StringBuffer(int capacity)

Create an empty StringBuffer with the specified initial capacity.

Parameters:

Throws:


StringBuffer

public StringBuffer(java.lang.String str)

Create a new StringBuffer with the characters in the specified String. Initial capacity will be the size of the String plus 16.

Parameters:

Throws:


Method Details

append

public StringBuffer append(boolean bool)

Append the String value of the argument to this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

See Also:


append

public StringBuffer append(char[] data)

Append the char array to this StringBuffer. This is similar (but more efficient) than append(new String(data)), except in the case of null.

Parameters:

Returns:

Throws:

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append

public synchronized StringBuffer append(char ch)

Append the char to this StringBuffer.

Parameters:

Returns:


append

public synchronized StringBuffer append(char[] data, int offset, int count)

Append part of the char array to this StringBuffer. This is similar (but more efficient) than append(new String(data, offset, count)), except in the case of null.

Parameters:

Returns:

Throws:


append

public StringBuffer append(double dnum)

Append the String value of the argument to this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

See Also:


append

public StringBuffer append(float fnum)

Append the String value of the argument to this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

See Also:


append

public StringBuffer append(int inum)

Append the String value of the argument to this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

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append

public StringBuffer append(java.lang.Object obj)

Append the String value of the argument to this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

See Also:


append

public synchronized StringBuffer append(java.lang.String str)

Append the String to this StringBuffer. If str is null, the String "null" is appended.

Parameters:

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append

public synchronized StringBuffer append(java.lang.StringBuffer stringBuffer)

Append the StringBuffer value of the argument to this StringBuffer. This behaves the same as append((Object) stringBuffer), except it is more efficient.

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append

public StringBuffer append(long lnum)

Append the String value of the argument to this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

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capacity

public synchronized int capacity()

Get the total number of characters this StringBuffer can support before it must be grown. Not to be confused with length.

Returns:

See Also:


charAt

public synchronized char charAt(int index)

Get the character at the specified index.

Parameters:

Returns:

Throws:


delete

public synchronized StringBuffer delete(int start, int end)

Delete characters from this StringBuffer. delete(10, 12) will delete 10 and 11, but not 12. It is harmless for end to be larger than length().

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deleteCharAt

public StringBuffer deleteCharAt(int index)

Delete a character from this StringBuffer.

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ensureCapacity

public synchronized void ensureCapacity(int minimumCapacity)

Increase the capacity of this 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.

Parameters:

See Also:


getChars

public synchronized void getChars(int srcOffset, int srcEnd, char[] dst, int dstOffset)

Get the specified array of characters. srcOffset - srcEnd characters will be copied into the array you pass in.

Parameters:

Throws:

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indexOf

public int indexOf(java.lang.String str)

Finds the first instance of a substring in this StringBuffer.

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indexOf

public synchronized int indexOf(java.lang.String str, int fromIndex)

Finds the first instance of a String in this StringBuffer, starting at a given index. If starting index is less than 0, the search starts at the beginning of this String. If the starting index is greater than the length of this String, or the substring is not found, -1 is returned.

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insert

public StringBuffer insert(int offset, boolean bool)

Insert the String value of the argument into this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

Throws:

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insert

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

Insert the char[] argument into this StringBuffer.

Parameters:

Returns:

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insert

public synchronized StringBuffer insert(int offset, char ch)

Insert the char argument into this StringBuffer.

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insert

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

Insert a subarray of the char[] argument into this StringBuffer.

Since:Parameters:

Returns:

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insert

public StringBuffer insert(int offset, double dnum)

Insert the String value of the argument into this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

Throws:

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insert

public StringBuffer insert(int offset, float fnum)

Insert the String value of the argument into this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

Throws:

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insert

public StringBuffer insert(int offset, int inum)

Insert the String value of the argument into this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

Throws:

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insert

public StringBuffer insert(int offset, java.lang.Object obj)

Insert the String value of the argument into this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

Throws:

See Also:


insert

public synchronized StringBuffer insert(int offset, java.lang.String str)

Insert the String argument into this StringBuffer. If str is null, the String "null" is used instead.

Parameters:

Returns:

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insert

public StringBuffer insert(int offset, long lnum)

Insert the String value of the argument into this StringBuffer. Uses String.valueOf() to convert to String.

Parameters:

Returns:

Throws:

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lastIndexOf

public int lastIndexOf(java.lang.String str)

Finds the last instance of a substring in this StringBuffer.

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lastIndexOf

public synchronized int lastIndexOf(java.lang.String str, int fromIndex)

Finds the last instance of a String in this StringBuffer, starting at a given index. If starting index is greater than the maximum valid index, then the search begins at the end of this String. If the starting index is less than zero, or the substring is not found, -1 is returned.

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length

public synchronized int length()

Get the length of the String this StringBuffer would create. Not to be confused with the capacity of the StringBuffer.

Returns:

See Also:


replace

public synchronized StringBuffer replace(int start, int end, java.lang.String str)

Replace characters between index start (inclusive) and end (exclusive) with str. If end is larger than the size of this StringBuffer, all characters after start are replaced.

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reverse

public synchronized StringBuffer reverse()

Reverse the characters in this StringBuffer. The same sequence of characters exists, but in the reverse index ordering.

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setCharAt

public synchronized void setCharAt(int index, char ch)

Set the character at the specified index.

Parameters:

Throws:


setLength

public synchronized void setLength(int newLength)

Set the length of this StringBuffer. If the new length is greater than the current length, all the new characters are set to '\0'. If the new length is less than the current length, the first newLength characters of the old array will be preserved, and the remaining characters are truncated.

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subSequence

public CharSequence subSequence(int beginIndex, int endIndex)

Creates a substring of this StringBuffer, starting at a specified index and ending at one character before a specified index. This is implemented the same as substring(beginIndex, endIndex), to satisfy the CharSequence interface.

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substring

public String substring(int beginIndex)

Creates a substring of this StringBuffer, starting at a specified index and ending at the end of this StringBuffer.

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substring

public synchronized String substring(int beginIndex, int endIndex)

Creates a substring of this StringBuffer, starting at a specified index and ending at one character before a specified index.

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toString

public String toString()

Convert this StringBuffer to a String. The String is composed of the characters currently in this StringBuffer. Note that the result is a copy, and that future modifications to this buffer do not affect the String.

Returns: