java.lang包学习--String，StringBuffer类

在lang包中，常用的类也是大家非常熟悉的一个就是String类了，说到String就不能不想到StringBuffer

1.String和StringBuffer的区别

String类描述了固定长度的字符串，内容不变，适用于字符串常量；StringBuffer描述的是长度可变且内容可变的字符串，适用于对字符串中的字符进行各种操作的字符串常量。

2.String类的方法

String类可以说是一个宝藏，每一个方法都是那么重要，是我们编程过程经常会遇到会使用的一个类，看看String类提供的方法

Method Summary
char	charAt(int index)           Returns the char value 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 String.
int	compareTo(String anotherString)           Compares two strings lexicographically.
int	compareToIgnoreCase(String str)           Compares two strings lexicographically, ignoring case differences.
String	concat(String str)           Concatenates the specified string to the end of this string.
boolean	contains(CharSequence s)           Returns true if and only if this string contains the specified sequence of char values.
boolean	contentEquals(CharSequence cs)           Returns true if and only if this String represents the same sequence of char values as the specified sequence.
boolean	contentEquals(StringBuffer sb)           Returns true if and only if this String represents the same sequence of characters as the specified StringBuffer.
static String	copyValueOf(char[] data)           Returns a String that represents the character sequence in the array specified.
static String	copyValueOf(char[] data,            int offset,            int count)           Returns a String that represents the character sequence in the array specified.
boolean	endsWith(String suffix)           Tests if this string ends with the specified suffix.
boolean	equals(Object anObject)           Compares this string to the specified object.
boolean	equalsIgnoreCase(String anotherString)           Compares this String to another String, ignoring case considerations.
static String	format(Locale l,       String format,       Object... args)           Returns a formatted string using the specified locale, format string, and arguments.
static String	format(String format,       Object... args)           Returns a formatted string using the specified format string and arguments.
byte[]	getBytes()           Encodes this String into a sequence of bytes using the platform's default charset, storing the result into a new byte array.
void	getBytes(int srcBegin,         int srcEnd,         byte[] dst,         int dstBegin)           Deprecated. This method does not properly convert characters into bytes. As of JDK 1.1, the preferred way to do this is via the getBytes() method, which uses the platform's default charset.
byte[]	getBytes(String charsetName)           Encodes this String into a sequence of bytes using the named charset, storing the result into a new byte array.
void	getChars(int srcBegin,         int srcEnd,         char[] dst,         int dstBegin)           Copies characters from this string into the destination character array.
int	hashCode()           Returns a hash code for this string.
int	indexOf(int ch)           Returns the index within this string of the first occurrence of the specified character.
int	indexOf(int ch,        int fromIndex)           Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index.
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.
String	intern()           Returns a canonical representation for the string object.
int	lastIndexOf(int ch)           Returns the index within this string of the last occurrence of the specified character.
int	lastIndexOf(int ch,            int fromIndex)           Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index.
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, searching backward starting at the specified index.
int	length()           Returns the length of this string.
boolean	matches(String regex)           Tells whether or not this string matches the given regular expression.
int	offsetByCodePoints(int index,                   int codePointOffset)           Returns the index within this String that is offset from the given index by codePointOffset code points.
boolean	regionMatches(boolean ignoreCase,              int toffset,              String other,              int ooffset,              int len)           Tests if two string regions are equal.
boolean	regionMatches(int toffset,              String other,              int ooffset,              int len)           Tests if two string regions are equal.
String	replace(char oldChar,        char newChar)           Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.
String	replace(CharSequence target,        CharSequence replacement)           Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence.
String	replaceAll(String regex,           String replacement)           Replaces each substring of this string that matches the given regular expression with the given replacement.
String	replaceFirst(String regex,             String replacement)           Replaces the first substring of this string that matches the given regular expression with the given replacement.
String[]	split(String regex)           Splits this string around matches of the given  regular expression.
String[]	split(String regex,      int limit)           Splits this string around matches of the given  regular expression.
boolean	startsWith(String prefix)            Tests if this string starts with the specified prefix.
boolean	startsWith(String prefix,           int toffset)           Tests if this string starts with the specified prefix beginning a specified index.
CharSequence	subSequence(int beginIndex,            int endIndex)           Returns a new character sequence that is a subsequence of this sequence.
String	substring(int beginIndex)           Returns a new string that is a substring of this string.
String	substring(int beginIndex,          int endIndex)           Returns a new string that is a substring of this string.
char[]	toCharArray()           Converts this string to a new character array.
String	toLowerCase()           Converts all of the characters in this String to lower case using the rules of the default locale.
String	toLowerCase(Locale locale)           Converts all of the characters in this String to lower case using the rules of the given Locale.
String	toString()           This object (which is already a string!) is itself returned.
String	toUpperCase()           Converts all of the characters in this String to upper case using the rules of the default locale.
String	toUpperCase(Locale locale)           Converts all of the characters in this String to upper case using the rules of the given Locale.
String	trim()           Returns a copy of the string, with leading and trailing whitespace omitted.
static String	valueOf(boolean b)           Returns the string representation of the boolean argument.
static String	valueOf(char c)           Returns the string representation of the char argument.
static String	valueOf(char[] data)           Returns the string representation of the char array argument.
static String	valueOf(char[] data,        int offset,        int count)           Returns the string representation of a specific subarray of the char array argument.
static String	valueOf(double d)           Returns the string representation of the double argument.
static String	valueOf(float f)           Returns the string representation of the float argument.
static String	valueOf(int i)           Returns the string representation of the int argument.
static String	valueOf(long l)           Returns the string representation of the long argument.
static String	valueOf(Object obj)           Returns the string representation of the Object argument.

其中从Object父类继承的有

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

 3.StringBuffer类的方法

Method Summary
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.

Methods inherited from class java.lang.Object

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

 

wait