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javaSE-常用类-StringBufferAndStringBuilder

2014-01-16 20:11 585 查看

StringBuffer

字符串的组成原理就是通过该类实现的。

StringBuffer可以对字符串内容进行增删。

StringBuffer是一个容器。

很多方法与String相同。

StingBuffer是可变长度的。

StringBuffer特有方法

StringBuffer append(int x);

StringBuffer delete(int start, int end );

StringBuffer insert(int index,String str);

StringBuffer reverse();

JDK1.5出现一个StringBuilder，区别是StringBuffer是同步的，StringBuilder是非同步的。

public static void main(String[] args) {

/*
* StringBuffer,字符串缓冲区。 特点： 1，可以存储任意类型的数据。 2，长度不固定。
* 3，无论存储什么类型的元素，存储进来以后最终都会变成字符串。
*
*
* 容器常见功能： 1，添加，插入。 append insert./ 2，删除。
*
* 3，替换。
*
*
* JDK1.5版本出现了StringBuilder。 StringBuffer是线程安全的。 StringBuilder是线程不安全的。
*/

// 创建一个字符串缓冲区对象。
StringBuffer sb = new StringBuffer();

// StringBuilder sb = new StringBuilder();

// 添加元素。
// sb.append("abc").append(true);
// sb.append(new Object());
// System.out.println(sb.toString());
// System.out.println(sb.length());

sb.append("abcd");

// 想要在任意位置插入指定的数据。
sb.insert(2, "qq");// abqqcd
// 删除。
// sb.delete(1, 3);

// 替换。
// sb.replace(1, 4, "ak47");
// sb.reverse();

// sb.setCharAt(2, 'K');

sb.setLength(3);
sb.setLength(6);
System.out.println(sb + "-");

String str = "a" + 7 + 'q' + true;
//这两者等价
str = new StringBuffer().append("a").append(7).append('q').append(true)
.toString();
}

Constructor Summary

Constructors

Constructor and Description
StringBuffer() Constructs a string buffer with no characters in it and an initial capacity of 16 characters.
StringBuffer(CharSequence seq) 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(String str) Constructs a string buffer initialized to the contents of the specified string.

Method Summary

Methods

Modifier and Type	Method and Description
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(CharSequence s) Appends the specified CharSequence to this sequence.
StringBuffer	append(CharSequence s, 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(Object obj) Appends the string representation of the Object argument.
StringBuffer	append(String str) Appends the specified string to this character sequence.
StringBuffer	append(StringBuffer sb) 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(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.
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, CharSequence s) Inserts the specified CharSequence into this sequence.
StringBuffer	insert(int dstOffset, CharSequence s, 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, Object obj) Inserts the string representation of the Object argument into this character sequence.
StringBuffer	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.
StringBuffer	replace(int start, int end, String str) 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.

java.lang

Class StringBuilder

java.lang.Object

java.lang.StringBuilder

All Implemented Interfaces:Serializable, Appendable, CharSequence

Constructor Summary

Constructors

Constructor and Description
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

Methods

Modifier and Type	Method and Description
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.

总结 StringBuffer是线程安全的StringBulider是线程不安全的

方法体内用StringBulider类里面的变量用StringBuffer

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