java.lang
Class StringBuilder

java.lang.Object
  java.lang.StringBuilder

All Implemented Interfaces:

Serializable, Appendable, CharSequence

public final class StringBuilder
extends Object
implements Serializable, CharSequence

A mutable sequence of characters. This class provides an API compatible with StringBuffer, but with no guarantee of synchronization. This class is designed for use as a drop-in replacement for StringBuffer in places where the string buffer was being used by a single thread (as is generally the case). Where possible, it is recommended that this class be used in preference to StringBuffer as it will be faster under most implementations.

The principal operations on a StringBuilder 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 builder. The append method always adds these characters at the end of the builder; the insert method adds the characters at a specified point.

For example, if z refers to a string builder object whose current contents are "start", then the method call z.append("le") would cause the string builder to contain "startle", whereas z.insert(4, "le") would alter the string builder to contain "starlet".

In general, if sb refers to an instance of a StringBuilder, then sb.append(x) has the same effect as sb.insert(sb.length(), x). Every string builder has a capacity. As long as the length of the character sequence contained in the string builder does not exceed the capacity, it is not necessary to allocate a new internal buffer. If the internal buffer overflows, it is automatically made larger.

Instances of StringBuilder are not safe for use by multiple threads. If such synchronization is required then it is recommended that StringBuffer be used.

Since:

1.5

See Also:

StringBuffer, String, Serialized Form

Constructor Summary

StringBuilder()
Constructs a string builder with no characters in it and an initial capacity of 16 characters.

StringBuilder(CharSequence seq)
Constructs a string builder that contains the same characters as the specified CharSequence.

StringBuilder(int capacity)
Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.

StringBuilder(String str)
Constructs a string builder initialized to the contents of the specified string.

Method Summary

StringBuilder	append(boolean b) Appends the string representation of the boolean argument to the sequence.
StringBuilder	append(char c) Appends the string representation of the char argument to this sequence.
StringBuilder	append(char[] str) Appends the string representation of the char array argument to this sequence.
StringBuilder	append(char[] str, int offset, int len) Appends the string representation of a subarray of the char array argument to this sequence.
StringBuilder	append(CharSequence s) Appends the specified character sequence to this Appendable.
StringBuilder	append(CharSequence s, int start, int end) Appends a subsequence of the specified CharSequence to this sequence.
StringBuilder	append(double d) Appends the string representation of the double argument to this sequence.
StringBuilder	append(float f) Appends the string representation of the float argument to this sequence.
StringBuilder	append(int i) Appends the string representation of the int argument to this sequence.
StringBuilder	append(long lng) Appends the string representation of the long argument to this sequence.
StringBuilder	append(Object obj) Appends the string representation of the Object argument.
StringBuilder	append(String str) Appends the specified string to this character sequence.
StringBuilder	append(StringBuffer sb) Appends the specified StringBuffer to this sequence.
StringBuilder	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.
StringBuilder	delete(int start, int end) Removes the characters in a substring of this sequence.
StringBuilder	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.
StringBuilder	insert(int offset, boolean b) Inserts the string representation of the boolean argument into this sequence.
StringBuilder	insert(int offset, char c) Inserts the string representation of the char argument into this sequence.
StringBuilder	insert(int offset, char[] str) Inserts the string representation of the char array argument into this sequence.
StringBuilder	insert(int index, char[] str, int offset, int len) Inserts the string representation of a subarray of the str array argument into this sequence.
StringBuilder	insert(int dstOffset, CharSequence s) Inserts the specified CharSequence into this sequence.
StringBuilder	insert(int dstOffset, CharSequence s, int start, int end) Inserts a subsequence of the specified CharSequence into this sequence.
StringBuilder	insert(int offset, double d) Inserts the string representation of the double argument into this sequence.
StringBuilder	insert(int offset, float f) Inserts the string representation of the float argument into this sequence.
StringBuilder	insert(int offset, int i) Inserts the string representation of the second int argument into this sequence.
StringBuilder	insert(int offset, long l) Inserts the string representation of the long argument into this sequence.
StringBuilder	insert(int offset, Object obj) Inserts the string representation of the Object argument into this character sequence.
StringBuilder	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.
StringBuilder	replace(int start, int end, String str) Replaces the characters in a substring of this sequence with characters in the specified String.
StringBuilder	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

Methods inherited from interface java.lang.CharSequence

charAt, length, subSequence

Constructor Detail

StringBuilder

public StringBuilder()

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

StringBuilder

public StringBuilder(int capacity)

Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.

Parameters:

capacity - the initial capacity.

Throws:

NegativeArraySizeException - if the capacity argument is less than 0.

StringBuilder

public StringBuilder(