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java.lang.Object
- java.lang.String

All Implemented Interfaces:
Serializable,CharSequence,Comparable<String>
```
public final classStringextendsObjectimplementsSerializable,Comparable<String>,CharSequence
```
TheString class represents character strings. All string literals in Java programs, such as"abc", are implemented as instances of this class.
Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. For example:
```
     String str = "abc";
```
is equivalent to:
```
     char data[] = {'a', 'b', 'c'};     String str = new String(data);
```
Here are some more examples of how strings can be used:
```
     System.out.println("abc");     String cde = "cde";     System.out.println("abc" + cde);     String c = "abc".substring(2,3);     String d = cde.substring(1, 2);
```
The classString includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for extracting substrings, and for creating a copy of a string with all characters translated to uppercase or to lowercase. Case mapping is based on the Unicode Standard version specified by theCharacter class.
The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through theStringBuilder(orStringBuffer) class and itsappend method. String conversions are implemented through the methodtoString, defined byObject and inherited by all classes in Java. For additional information on string concatenation and conversion, see Gosling, Joy, and Steele,The Java Language Specification.
Unless otherwise noted, passing anull argument to a constructor or method in this class will cause aNullPointerException to be thrown.
AString represents a string in the UTF-16 format in whichsupplementary characters are represented bysurrogate pairs (see the sectionUnicode Character Representations in theCharacter class for more information). Index values refer tochar code units, so a supplementary character uses two positions in aString.
TheString class provides methods for dealing with Unicode code points (i.e., characters), in addition to those for dealing with Unicode code units (i.e.,char values).
Since:
JDK1.0
See Also:
Object.toString(),StringBuffer,StringBuilder,Charset,Serialized Form

Field Summary
Fields
Modifier and Type Field Description
staticComparator<String> CASE_INSENSITIVE_ORDER
A Comparator that ordersString objects as bycompareToIgnoreCase.

Fields
Modifier and Type	Field	Description
`staticComparator<String>`	`CASE_INSENSITIVE_ORDER`	A Comparator that orders`String` objects as by`compareToIgnoreCase`.

Constructor Summary

Constructors
Constructor	Description
`String()`	Initializes a newly created`String` object so that it represents an empty character sequence.
`String(byte[] bytes)`	Constructs a new`String` by decoding the specified array of bytes using the platform's default charset.
`String(byte[] bytes,Charset charset)`	Constructs a new`String` by decoding the specified array of bytes using the specifiedcharset.
`String(byte[] ascii, int hibyte)`	Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the`String` constructors that take a`Charset`, charset name, or that use the platform's default charset.
`String(byte[] bytes, int offset, int length)`	Constructs a new`String` by decoding the specified subarray of bytes using the platform's default charset.
`String(byte[] bytes, int offset, int length,Charset charset)`	Constructs a new`String` by decoding the specified subarray of bytes using the specifiedcharset.
`String(byte[] ascii, int hibyte, int offset, int count)`	Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the`String` constructors that take a`Charset`, charset name, or that use the platform's default charset.
`String(byte[] bytes, int offset, int length,String charsetName)`	Constructs a new`String` by decoding the specified subarray of bytes using the specified charset.
`String(byte[] bytes,String charsetName)`	Constructs a new`String` by decoding the specified array of bytes using the specifiedcharset.
`String(char[] value)`	Allocates a new`String` so that it represents the sequence of characters currently contained in the character array argument.
`String(char[] value, int offset, int count)`	Allocates a new`String` that contains characters from a subarray of the character array argument.
`String(int[] codePoints, int offset, int count)`	Allocates a new`String` that contains characters from a subarray of theUnicode code point array argument.
`String(String original)`	Initializes a newly created`String` object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string.
`String(StringBuffer buffer)`	Allocates a new string that contains the sequence of characters currently contained in the string buffer argument.
`String(StringBuilder builder)`	Allocates a new string that contains the sequence of characters currently contained in the string builder argument.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method	Description
`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)`	Compares this string to the specified`CharSequence`.
`boolean`	`contentEquals(StringBuffer sb)`	Compares this string to the specified`StringBuffer`.
`staticString`	`copyValueOf(char[] data)`	Equivalent to`valueOf(char[])`.
`staticString`	`copyValueOf(char[] data, int offset, int count)`	Equivalent to`valueOf(char[], int, int)`.
`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.
`staticString`	`format(Locale l,String format,Object... args)`	Returns a formatted string using the specified locale, format string, and arguments.
`staticString`	`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.
`byte[]`	`getBytes(Charset charset)`	Encodes this`String` into a sequence of bytes using the givencharset, 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.
`boolean`	`isEmpty()`	Returns`true` if, and only if,`length()` is`0`.
`staticString`	`join(CharSequence delimiter,CharSequence... elements)`	Returns a new String composed of copies of the`CharSequence elements` joined together with a copy of the specified`delimiter`.
`staticString`	`join(CharSequence delimiter,Iterable<? extendsCharSequence> elements)`	Returns a new`String` composed of copies of the`CharSequence elements` joined together with a copy of the specified`delimiter`.
`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 last 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 givenregular 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 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 givenregular expression with the given replacement.
`String`	`replaceFirst(String regex,String replacement)`	Replaces the first substring of this string that matches the givenregular expression with the given replacement.
`String[]`	`split(String regex)`	Splits this string around matches of the givenregular expression.
`String[]`	`split(String regex, int limit)`	Splits this string around matches of the givenregular expression.
`boolean`	`startsWith(String prefix)`	Tests if this string starts with the specified prefix.
`boolean`	`startsWith(String prefix, int toffset)`	Tests if the substring of this string beginning at the specified index starts with the specified prefix.
`CharSequence`	`subSequence(int beginIndex, int endIndex)`	Returns a character sequence that is a subsequence of this sequence.
`String`	`substring(int beginIndex)`	Returns a string that is a substring of this string.
`String`	`substring(int beginIndex, int endIndex)`	Returns a 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 string whose value is this string, with any leading and trailing whitespace removed.
`staticString`	`valueOf(boolean b)`	Returns the string representation of the`boolean` argument.
`staticString`	`valueOf(char c)`	Returns the string representation of the`char` argument.
`staticString`	`valueOf(char[] data)`	Returns the string representation of the`char` array argument.
`staticString`	`valueOf(char[] data, int offset, int count)`	Returns the string representation of a specific subarray of the`char` array argument.
`staticString`	`valueOf(double d)`	Returns the string representation of the`double` argument.
`staticString`	`valueOf(float f)`	Returns the string representation of the`float` argument.
`staticString`	`valueOf(int i)`	Returns the string representation of the`int` argument.
`staticString`	`valueOf(long l)`	Returns the string representation of the`long` argument.
`staticString`	`valueOf(Object obj)`	Returns the string representation of the`Object` argument.

Methods inherited from class java.lang.Object
clone,finalize,getClass,notify,notifyAll,wait,wait,wait

Methods inherited from interface java.lang.CharSequence
chars,codePoints

Field Detail
- CASE_INSENSITIVE_ORDER
```
public static final Comparator<String> CASE_INSENSITIVE_ORDER
```
  A Comparator that ordersString objects as bycompareToIgnoreCase. This comparator is serializable.
  Note that this Comparator doesnot take locale into account, and will result in an unsatisfactory ordering for certain locales. The java.text package providesCollators to allow locale-sensitive ordering.
  Since:
  1.2
  See Also:
  Collator.compare(String, String)

Constructor Detail
- String
```
public String()
```
  Initializes a newly createdString object so that it represents an empty character sequence. Note that use of this constructor is unnecessary since Strings are immutable.
- String
```
public String(String original)
```
  Initializes a newly createdString object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string. Unless an explicit copy oforiginal is needed, use of this constructor is unnecessary since Strings are immutable.
  Parameters:
  original - AString
- String
```
public String(char[] value)
```
  Allocates a newString so that it represents the sequence of characters currently contained in the character array argument. The contents of the character array are copied; subsequent modification of the character array does not affect the newly created string.
  Parameters:
  value - The initial value of the string
- String
```
public String(char[] value,              int offset,              int count)
```
  Allocates a newString that contains characters from a subarray of the character array argument. Theoffset argument is the index of the first character of the subarray and thecount argument specifies the length of the subarray. The contents of the subarray are copied; subsequent modification of the character array does not affect the newly created string.
  Parameters:
  value - Array that is the source of characters
  offset - The initial offset
  count - The length
  Throws:
  IndexOutOfBoundsException - If theoffset andcount arguments index characters outside the bounds of thevalue array
- String
```
public String(int[] codePoints,              int offset,              int count)
```
  Allocates a newString that contains characters from a subarray of theUnicode code point array argument. Theoffset argument is the index of the first code point of the subarray and thecount argument specifies the length of the subarray. The contents of the subarray are converted tochars; subsequent modification of theint array does not affect the newly created string.
  Parameters:
  codePoints - Array that is the source of Unicode code points
  offset - The initial offset
  count - The length
  Throws:
  IllegalArgumentException - If any invalid Unicode code point is found incodePoints
  IndexOutOfBoundsException - If theoffset andcount arguments index characters outside the bounds of thecodePoints array
  Since:
  1.5
- String
```
@Deprecatedpublic String(byte[] ascii,                          int hibyte,                          int offset,                          int count)
```
  Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via theString constructors that take aCharset, charset name, or that use the platform's default charset.
  Allocates a newString constructed from a subarray of an array of 8-bit integer values.
  Theoffset argument is the index of the first byte of the subarray, and thecount argument specifies the length of the subarray.
  Eachbyte in the subarray is converted to achar as specified in the method above.
  Parameters:
  ascii - The bytes to be converted to characters
  hibyte - The top 8 bits of each 16-bit Unicode code unit
  offset - The initial offset
  count - The length
  Throws:
  IndexOutOfBoundsException - If theoffset orcount argument is invalid
  See Also:
  String(byte[], int),String(byte[], int, int, java.lang.String),String(byte[], int, int, java.nio.charset.Charset),String(byte[], int, int),String(byte[], java.lang.String),String(byte[], java.nio.charset.Charset),String(byte[])
- String
```
@Deprecatedpublic String(byte[] ascii,                          int hibyte)
```
  Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via theString constructors that take aCharset, charset name, or that use the platform's default charset.
  Allocates a newString containing characters constructed from an array of 8-bit integer values. Each charactercin the resulting string is constructed from the corresponding componentb in the byte array such that:
```
c == (char)(((hibyte & 0xff) << 8)                         | (b & 0xff))
```
  Parameters:
  ascii - The bytes to be converted to characters
  hibyte - The top 8 bits of each 16-bit Unicode code unit
  See Also:
  String(byte[], int, int, java.lang.String),String(byte[], int, int, java.nio.charset.Charset),String(byte[], int, int),String(byte[], java.lang.String),String(byte[], java.nio.charset.Charset),String(byte[])
- String
```
public String(byte[] bytes,              int offset,              int length,String charsetName)       throwsUnsupportedEncodingException
```
  Constructs a newString by decoding the specified subarray of bytes using the specified charset. The length of the newString is a function of the charset, and hence may not be equal to the length of the subarray.
  The behavior of this constructor when the given bytes are not valid in the given charset is unspecified. TheCharsetDecoder class should be used when more control over the decoding process is required.
  Parameters:
  bytes - The bytes to be decoded into characters
  offset - The index of the first byte to decode
  length - The number of bytes to decode
  charsetName - The name of a supportedcharset
  Throws:
  UnsupportedEncodingException - If the named charset is not supported
  IndexOutOfBoundsException - If theoffset andlength arguments index characters outside the bounds of thebytes array
  Since:
  JDK1.1
- String
```
public String(byte[] bytes,              int offset,              int length,Charset charset)
```
  Constructs a newString by decoding the specified subarray of bytes using the specifiedcharset. The length of the newString is a function of the charset, and hence may not be equal to the length of the subarray.
  This method always replaces malformed-input and unmappable-character sequences with this charset's default replacement string. TheCharsetDecoder class should be used when more control over the decoding process is required.
  Parameters:
  bytes - The bytes to be decoded into characters
  offset - The index of the first byte to decode
  length - The number of bytes to decode
  charset - Thecharset to be used to decode thebytes
  Throws:
  IndexOutOfBoundsException - If theoffset andlength arguments index characters outside the bounds of thebytes array
  Since:
  1.6
- String
```
public String(byte[] bytes,String charsetName)       throwsUnsupportedEncodingException
```
  Constructs a newString by decoding the specified array of bytes using the specifiedcharset. The length of the newString is a function of the charset, and hence may not be equal to the length of the byte array.
  The behavior of this constructor when the given bytes are not valid in the given charset is unspecified. TheCharsetDecoder class should be used when more control over the decoding process is required.
  Parameters:
  bytes - The bytes to be decoded into characters
  charsetName - The name of a supportedcharset
  Throws:
  UnsupportedEncodingException - If the named charset is not supported
  Since:
  JDK1.1
- String
```
public String(byte[] bytes,Charset charset)
```
  Constructs a newString by decoding the specified array of bytes using the specifiedcharset. The length of the newString is a function of the charset, and hence may not be equal to the length of the byte array.
  This method always replaces malformed-input and unmappable-character sequences with this charset's default replacement string. TheCharsetDecoder class should be used when more control over the decoding process is required.
  Parameters:
  bytes - The bytes to be decoded into characters
  charset - Thecharset to be used to decode thebytes
  Since:
  1.6
- String
```
public String(byte[] bytes,              int offset,              int length)
```
  Constructs a newString by decoding the specified subarray of bytes using the platform's default charset. The length of the newString is a function of the charset, and hence may not be equal to the length of the subarray.
  The behavior of this constructor when the given bytes are not valid in the default charset is unspecified. TheCharsetDecoder class should be used when more control over the decoding process is required.
  Parameters:
  bytes - The bytes to be decoded into characters
  offset - The index of the first byte to decode
  length - The number of bytes to decode
  Throws:
  IndexOutOfBoundsException - If theoffset and thelength arguments index characters outside the bounds of thebytes array
  Since:
  JDK1.1
- String
```
public String(byte[] bytes)
```
  Constructs a newString by decoding the specified array of bytes using the platform's default charset. The length of the newString is a function of the charset, and hence may not be equal to the length of the byte array.
  The behavior of this constructor when the given bytes are not valid in the default charset is unspecified. TheCharsetDecoder class should be used when more control over the decoding process is required.
  Parameters:
  bytes - The bytes to be decoded into characters
  Since:
  JDK1.1
- String
```
public String(StringBuffer buffer)
```
  Allocates a new string that contains the sequence of characters currently contained in the string buffer argument. The contents of the string buffer are copied; subsequent modification of the string buffer does not affect the newly created string.
  Parameters:
  buffer - AStringBuffer
- String
```
public String(StringBuilder builder)
```
  Allocates a new string that contains the sequence of characters currently contained in the string builder argument. The contents of the string builder are copied; subsequent modification of the string builder does not affect the newly created string.
  This constructor is provided to ease migration toStringBuilder. Obtaining a string from a string builder via thetoString method is likely to run faster and is generally preferred.
  Parameters:
  builder - AStringBuilder
  Since:
  1.5

Method Detail

length
```
public int length()
```
Returns the length of this string. The length is equal to the number ofUnicode code units in the string.
Specified by:
length in interface CharSequence
Returns:
the length of the sequence of characters represented by this object.

isEmpty
```
public boolean isEmpty()
```
Returnstrue if, and only if,length() is0.
Returns:
true iflength() is0, otherwisefalse
Since:
1.6

charAt
```
public char charAt(int index)
```
Returns thechar value at the specified index. An index ranges from0 tolength() - 1. The firstchar value of the sequence is at index0, the next at index1, and so on, as for array indexing.
If thechar value specified by the index is asurrogate, the surrogate value is returned.
Specified by:
charAt in interface CharSequence
Parameters:
index - the index of thechar value.
Returns:
thechar value at the specified index of this string. The firstchar value is at index0.
Throws:
IndexOutOfBoundsException - if theindex argument is negative or not less than the length of this string.

codePointAt
```
public int codePointAt(int index)
```
Returns the character (Unicode code point) at the specified index. The index refers tochar values (Unicode code units) and ranges from0 tolength()- 1.
If thechar value specified at the given index is in the high-surrogate range, the following index is less than the length of thisString, and thechar value at the following index is in the low-surrogate range, then the supplementary code point corresponding to this surrogate pair is returned. Otherwise, thechar value at the given index is returned.
Parameters:
index - the index to thechar values
Returns:
the code point value of the character at theindex
Throws:
IndexOutOfBoundsException - if theindex argument is negative or not less than the length of this string.
Since:
1.5

codePointBefore
```
public int codePointBefore(int index)
```
Returns the character (Unicode code point) before the specified index. The index refers tochar values (Unicode code units) and ranges from1 tolength.
If thechar value at(index - 1) is in the low-surrogate range,(index - 2) is not negative, and thechar value at(index - 2) is in the high-surrogate range, then the supplementary code point value of the surrogate pair is returned. If thechar value atindex - 1 is an unpaired low-surrogate or a high-surrogate, the surrogate value is returned.
Parameters:
index - the index following the code point that should be returned
Returns:
the Unicode code point value before the given index.
Throws:
IndexOutOfBoundsException - if theindex argument is less than 1 or greater than the length of this string.
Since:
1.5

codePointCount
```
public int codePointCount(int beginIndex,                          int endIndex)
```
Returns the number of Unicode code points in the specified text range of thisString. The text range begins at the specifiedbeginIndex and extends to thechar at indexendIndex - 1. Thus the length (inchars) of the text range isendIndex-beginIndex. Unpaired surrogates within the text range count as one code point each.
Parameters:
beginIndex - the index to the firstchar of the text range.
endIndex - the index after the lastchar of the text range.
Returns:
the number of Unicode code points in the specified text range
Throws:
IndexOutOfBoundsException - if thebeginIndex is negative, orendIndex is larger than the length of thisString, orbeginIndex is larger thanendIndex.
Since:
1.5

offsetByCodePoints
```
public int offsetByCodePoints(int index,                              int codePointOffset)
```
Returns the index within thisString that is offset from the givenindex bycodePointOffset code points. Unpaired surrogates within the text range given byindex andcodePointOffset count as one code point each.
Parameters:
index - the index to be offset
codePointOffset - the offset in code points
Returns:
the index within thisString
Throws:
IndexOutOfBoundsException - ifindex is negative or larger then the length of thisString, or ifcodePointOffset is positive and the substring starting withindex has fewer thancodePointOffset code points, or ifcodePointOffset is negative and the substring beforeindex has fewer than the absolute value ofcodePointOffset code points.
Since:
1.5

getChars
```
public void getChars(int srcBegin,                     int srcEnd,                     char[] dst,                     int dstBegin)
```
Copies characters from this string into the destination character array.
The first character to be copied is at indexsrcBegin; the last character to be copied is at indexsrcEnd-1 (thus the total number of characters to be copied issrcEnd-srcBegin). The characters are copied into the subarray ofdst starting at indexdstBegin and ending at index:
```
     dstBegin + (srcEnd-srcBegin) - 1
```
Parameters:
srcBegin - index of the first character in the string to copy.
srcEnd - index after the last character in the string to copy.
dst - the destination array.
dstBegin - the start offset in the destination array.
Throws:
IndexOutOfBoundsException - If any of the following is true:
- srcBegin is negative.
- srcBegin is greater thansrcEnd
- srcEnd is greater than the length of this string
- dstBegin is negative
- dstBegin+(srcEnd-srcBegin) is larger thandst.length

getBytes
```
@Deprecatedpublic 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 thegetBytes() method, which uses the platform's default charset.
Copies characters from this string into the destination byte array. Each byte receives the 8 low-order bits of the corresponding character. The eight high-order bits of each character are not copied and do not participate in the transfer in any way.
The first character to be copied is at indexsrcBegin; the last character to be copied is at indexsrcEnd-1. The total number of characters to be copied issrcEnd-srcBegin. The characters, converted to bytes, are copied into the subarray ofdst starting at indexdstBegin and ending at index:
```
     dstBegin + (srcEnd-srcBegin) - 1
```
Parameters:
srcBegin - Index of the first character in the string to copy
srcEnd - Index after the last character in the string to copy
dst - The destination array
dstBegin - The start offset in the destination array
Throws:
IndexOutOfBoundsException - If any of the following is true:
- srcBegin is negative
- srcBegin is greater thansrcEnd
- srcEnd is greater than the length of this String
- dstBegin is negative
- dstBegin+(srcEnd-srcBegin) is larger thandst.length

getBytes
```
public byte[] getBytes(String charsetName)                throwsUnsupportedEncodingException
```
Encodes thisString into a sequence of bytes using the named charset, storing the result into a new byte array.
The behavior of this method when this string cannot be encoded in the given charset is unspecified. TheCharsetEncoder class should be used when more control over the encoding process is required.
Parameters:
charsetName - The name of a supportedcharset
Returns:
The resultant byte array
Throws:
UnsupportedEncodingException - If the named charset is not supported
Since:
JDK1.1

getBytes
```
public byte[] getBytes(Charset charset)
```
Encodes thisString into a sequence of bytes using the givencharset, storing the result into a new byte array.
This method always replaces malformed-input and unmappable-character sequences with this charset's default replacement byte array. TheCharsetEncoder class should be used when more control over the encoding process is required.
Parameters:
charset - TheCharset to be used to encode theString
Returns:
The resultant byte array
Since:
1.6

getBytes
```
public byte[] getBytes()
```
Encodes thisString into a sequence of bytes using the platform's default charset, storing the result into a new byte array.
The behavior of this method when this string cannot be encoded in the default charset is unspecified. TheCharsetEncoder class should be used when more control over the encoding process is required.
Returns:
The resultant byte array
Since:
JDK1.1

equals
```
public boolean equals(Object anObject)
```
Compares this string to the specified object. The result istrue if and only if the argument is notnull and is aString object that represents the same sequence of characters as this object.
Overrides:
equals in class Object
Parameters:
anObject - The object to compare thisString against
Returns:
true if the given object represents aString equivalent to this string,false otherwise
See Also:
compareTo(String),equalsIgnoreCase(String)

contentEquals
```
public boolean contentEquals(StringBuffer sb)
```
Compares this string to the specifiedStringBuffer. The result istrue if and only if thisString represents the same sequence of characters as the specifiedStringBuffer. This method synchronizes on theStringBuffer.
Parameters:
sb - TheStringBuffer to compare thisString against
Returns:
true if thisString represents the same sequence of characters as the specifiedStringBuffer,false otherwise
Since:
1.4

contentEquals
```
public boolean contentEquals(CharSequence cs)
```
Compares this string to the specifiedCharSequence. The result istrue if and only if thisString represents the same sequence of char values as the specified sequence. Note that if theCharSequence is aStringBuffer then the method synchronizes on it.
Parameters:
cs - The sequence to compare thisString against
Returns:
true if thisString represents the same sequence of char values as the specified sequence,false otherwise
Since:
1.5

equalsIgnoreCase
```
public boolean equalsIgnoreCase(String anotherString)
```
Compares thisString to anotherString, ignoring case considerations. Two strings are considered equal ignoring case if they are of the same length and corresponding characters in the two strings are equal ignoring case.
Two charactersc1 andc2 are considered the same ignoring case if at least one of the following is true:
- The two characters are the same (as compared by the== operator)
- Applying the methodCharacter.toUpperCase(char) to each character produces the same result
- Applying the methodCharacter.toLowerCase(char) to each character produces the same result
Parameters:
anotherString - TheString to compare thisString against
Returns:
true if the argument is notnull and it represents an equivalentString ignoring case;false otherwise
See Also:
equals(Object)

compareTo
```
public int compareTo(String anotherString)
```
Compares two strings lexicographically. The comparison is based on the Unicode value of each character in the strings. The character sequence represented by thisString object is compared lexicographically to the character sequence represented by the argument string. The result is a negative integer if thisString object lexicographically precedes the argument string. The result is a positive integer if thisString object lexicographically follows the argument string. The result is zero if the strings are equal;compareTo returns0 exactly when theequals(Object) method would returntrue.
This is the definition of lexicographic ordering. If two strings are different, then either they have different characters at some index that is a valid index for both strings, or their lengths are different, or both. If they have different characters at one or more index positions, letk be the smallest such index; then the string whose character at positionk has the smaller value, as determined by using the < operator, lexicographically precedes the other string. In this case,compareTo returns the difference of the two character values at positionk in the two string -- that is, the value:
```
 this.charAt(k)-anotherString.charAt(k)
```
If there is no index position at which they differ, then the shorter string lexicographically precedes the longer string. In this case,compareTo returns the difference of the lengths of the strings -- that is, the value:
```
 this.length()-anotherString.length()
```
Specified by:
compareTo in interface Comparable<String>
Parameters:
anotherString - theString to be compared.
Returns:
the value0 if the argument string is equal to this string; a value less than0 if this string is lexicographically less than the string argument; and a value greater than0 if this string is lexicographically greater than the string argument.

compareToIgnoreCase
```
public int compareToIgnoreCase(String str)
```
Compares two strings lexicographically, ignoring case differences. This method returns an integer whose sign is that of callingcompareTo with normalized versions of the strings where case differences have been eliminated by callingCharacter.toLowerCase(Character.toUpperCase(character)) on each character.
Note that this method doesnot take locale into account, and will result in an unsatisfactory ordering for certain locales. The java.text package providescollators to allow locale-sensitive ordering.
Parameters:
str - theString to be compared.
Returns:
a negative integer, zero, or a positive integer as the specified String is greater than, equal to, or less than this String, ignoring case considerations.
Since:
1.2
See Also:
Collator.compare(String, String)

regionMatches
```
public boolean regionMatches(int toffset,String other,                             int ooffset,                             int len)
```
Tests if two string regions are equal.
A substring of thisString object is compared to a substring of the argument other. The result is true if these substrings represent identical character sequences. The substring of thisString object to be compared begins at indextoffset and has lengthlen. The substring of other to be compared begins at indexooffset and has lengthlen. The result isfalse if and only if at least one of the following is true:
- toffset is negative.
- ooffset is negative.
- toffset+len is greater than the length of thisString object.
- ooffset+len is greater than the length of the other argument.
- There is some nonnegative integerk less thanlen such that:this.charAt(toffset +k) != other.charAt(ooffset +k)
Parameters:
toffset - the starting offset of the subregion in this string.
other - the string argument.
ooffset - the starting offset of the subregion in the string argument.
len - the number of characters to compare.
Returns:
true if the specified subregion of this string exactly matches the specified subregion of the string argument;false otherwise.

regionMatches
```
public boolean regionMatches(boolean ignoreCase,                             int toffset,String other,                             int ooffset,                             int len)
```
Tests if two string regions are equal.
A substring of thisString object is compared to a substring of the argumentother. The result istrue if these substrings represent character sequences that are the same, ignoring case if and only ifignoreCase is true. The substring of thisString object to be compared begins at indextoffset and has lengthlen. The substring ofother to be compared begins at indexooffset and has lengthlen. The result isfalse if and only if at least one of the following is true:
- toffset is negative.
- ooffset is negative.
- toffset+len is greater than the length of thisString object.
- ooffset+len is greater than the length of the other argument.
- ignoreCase isfalse and there is some nonnegative integerk less thanlen such that:
```
 this.charAt(toffset+k) != other.charAt(ooffset+k)
```
- ignoreCase istrue and there is some nonnegative integerk less thanlen such that:
```
 Character.toLowerCase(this.charAt(toffset+k)) !=     Character.toLowerCase(other.charAt(ooffset+k))
```
  and:
```
 Character.toUpperCase(this.charAt(toffset+k)) !=         Character.toUpperCase(other.charAt(ooffset+k))
```
Parameters:
ignoreCase - iftrue, ignore case when comparing characters.
toffset - the starting offset of the subregion in this string.
other - the string argument.
ooffset - the starting offset of the subregion in the string argument.
len - the number of characters to compare.
Returns:
true if the specified subregion of this string matches the specified subregion of the string argument;false otherwise. Whether the matching is exact or case insensitive depends on theignoreCase argument.

startsWith
```
public boolean startsWith(String prefix,                          int toffset)
```
Tests if the substring of this string beginning at the specified index starts with the specified prefix.
Parameters:
prefix - the prefix.
toffset - where to begin looking in this string.
Returns:
true if the character sequence represented by the argument is a prefix of the substring of this object starting at indextoffset;false otherwise. The result isfalse iftoffset is negative or greater than the length of thisString object; otherwise the result is the same as the result of the expression
```
          this.substring(toffset).startsWith(prefix)
```

startsWith
```
public boolean startsWith(String prefix)
```
Tests if this string starts with the specified prefix.
Parameters:
prefix - the prefix.
Returns:
true if the character sequence represented by the argument is a prefix of the character sequence represented by this string;false otherwise. Note also thattrue will be returned if the argument is an empty string or is equal to thisString object as determined by theequals(Object) method.
Since:
1. 0

endsWith
```
public boolean endsWith(String suffix)
```
Tests if this string ends with the specified suffix.
Parameters:
suffix - the suffix.
Returns:
true if the character sequence represented by the argument is a suffix of the character sequence represented by this object;false otherwise. Note that the result will betrue if the argument is the empty string or is equal to thisString object as determined by theequals(Object) method.

hashCode
```
public int hashCode()
```
Returns a hash code for this string. The hash code for aString object is computed as
```
 s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
```
usingint arithmetic, wheres[i] is theith character of the string,n is the length of the string, and^ indicates exponentiation. (The hash value of the empty string is zero.)
Overrides:
hashCode in class Object
Returns:
a hash code value for this object.
See Also:
Object.equals(java.lang.Object),System.identityHashCode(java.lang.Object)

indexOf
```
public int indexOf(int ch)
```
Returns the index within this string of the first occurrence of the specified character. If a character with valuech occurs in the character sequence represented by thisString object, then the index (in Unicode code units) of the first such occurrence is returned. For values ofch in the range from 0 to 0xFFFF (inclusive), this is the smallest valuek such that:
```
 this.charAt(k) == ch
```
is true. For other values ofch, it is the smallest valuek such that:
```
 this.codePointAt(k) == ch
```
is true. In either case, if no such character occurs in this string, then-1 is returned.
Parameters:
ch - a character (Unicode code point).
Returns:
the index of the first occurrence of the character in the character sequence represented by this object, or-1 if the character does not occur.

indexOf
```
public 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.
If a character with valuech occurs in the character sequence represented by thisString object at an index no smaller thanfromIndex, then the index of the first such occurrence is returned. For values ofch in the range from 0 to 0xFFFF (inclusive), this is the smallest valuek such that:
```
 (this.charAt(k) == ch) && (k >= fromIndex)
```
is true. For other values ofch, it is the smallest valuek such that:
```
 (this.codePointAt(k) == ch) && (k >= fromIndex)
```
is true. In either case, if no such character occurs in this string at or after positionfromIndex, then-1 is returned.
There is no restriction on the value offromIndex. If it is negative, it has the same effect as if it were zero: this entire string may be searched. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string:-1 is returned.
All indices are specified inchar values (Unicode code units).
Parameters:
ch - a character (Unicode code point).
fromIndex - the index to start the search from.
Returns:
the index of the first occurrence of the character in the character sequence represented by this object that is greater than or equal tofromIndex, or-1 if the character does not occur.

lastIndexOf
```
public int lastIndexOf(int ch)
```
Returns the index within this string of the last occurrence of the specified character. For values ofch in the range from 0 to 0xFFFF (inclusive), the index (in Unicode code units) returned is the largest valuek such that:
```
 this.charAt(k) == ch
```
is true. For other values ofch, it is the largest valuek such that:
```
 this.codePointAt(k) == ch
```
is true. In either case, if no such character occurs in this string, then-1 is returned. TheString is searched backwards starting at the last character.
Parameters:
ch - a character (Unicode code point).
Returns:
the index of the last occurrence of the character in the character sequence represented by this object, or-1 if the character does not occur.

lastIndexOf
```
public 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. For values ofch in the range from 0 to 0xFFFF (inclusive), the index returned is the largest valuek such that:
```
 (this.charAt(k) == ch) && (k <= fromIndex)
```
is true. For other values ofch, it is the largest valuek such that:
```
 (this.codePointAt(k) == ch) && (k <= fromIndex)
```
is true. In either case, if no such character occurs in this string at or before positionfromIndex, then-1 is returned.
All indices are specified inchar values (Unicode code units).
Parameters:
ch - a character (Unicode code point).
fromIndex - the index to start the search from. There is no restriction on the value offromIndex. If it is greater than or equal to the length of this string, it has the same effect as if it were equal to one less than the length of this string: this entire string may be searched. If it is negative, it has the same effect as if it were -1: -1 is returned.
Returns:
the index of the last occurrence of the character in the character sequence represented by this object that is less than or equal tofromIndex, or-1 if the character does not occur before that point.

indexOf
```
public int indexOf(String str)
```
Returns the index within this string of the first occurrence of the specified substring.
The returned index is the smallest valuek for which:
```
 this.startsWith(str,k)
```
If no such value ofk exists, then-1 is returned.
Parameters:
str - the substring to search for.
Returns:
the index of the first occurrence of the specified substring, or-1 if there is no such occurrence.

indexOf
```
public 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.
The returned index is the smallest valuek for which:
```
k >= fromIndex && this.startsWith(str,k)
```
If no such value ofk exists, then-1 is returned.
Parameters:
str - the substring to search for.
fromIndex - the index from which to start the search.
Returns:
the index of the first occurrence of the specified substring, starting at the specified index, or-1 if there is no such occurrence.

lastIndexOf
```
public int lastIndexOf(String str)
```
Returns the index within this string of the last occurrence of the specified substring. The last occurrence of the empty string "" is considered to occur at the index valuethis.length().
The returned index is the largest valuek for which:
```
 this.startsWith(str,k)
```
If no such value ofk exists, then-1 is returned.
Parameters:
str - the substring to search for.
Returns:
the index of the last occurrence of the specified substring, or-1 if there is no such occurrence.

lastIndexOf
```
public 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.
The returned index is the largest valuek for which:
```
k <= fromIndex && this.startsWith(str,k)
```
If no such value ofk exists, then-1 is returned.
Parameters:
str - the substring to search for.
fromIndex - the index to start the search from.
Returns:
the index of the last occurrence of the specified substring, searching backward from the specified index, or-1 if there is no such occurrence.

substring
```
public String substring(int beginIndex)
```
Returns a string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string.
Examples:
```
 "unhappy".substring(2) returns "happy" "Harbison".substring(3) returns "bison" "emptiness".substring(9) returns "" (an empty string)
```
Parameters:
beginIndex - the beginning index, inclusive.
Returns:
the specified substring.
Throws:
IndexOutOfBoundsException - ifbeginIndex is negative or larger than the length of thisString object.

substring
```
public String substring(int beginIndex,                        int endIndex)
```
Returns a string that is a substring of this string. The substring begins at the specifiedbeginIndex and extends to the character at indexendIndex - 1. Thus the length of the substring isendIndex-beginIndex.
Examples:
```
 "hamburger".substring(4, 8) returns "urge" "smiles".substring(1, 5) returns "mile"
```
Parameters:
beginIndex - the beginning index, inclusive.
endIndex - the ending index, exclusive.
Returns:
the specified substring.
Throws:
IndexOutOfBoundsException - if thebeginIndex is negative, orendIndex is larger than the length of thisString object, orbeginIndex is larger thanendIndex.

subSequence
```
public CharSequence subSequence(int beginIndex,                                int endIndex)
```
Returns a character sequence that is a subsequence of this sequence.
An invocation of this method of the form
```
 str.subSequence(begin, end)
```
behaves in exactly the same way as the invocation
```
 str.substring(begin, end)
```
Specified by:
subSequence in interface CharSequence
API Note:
This method is defined so that theString class can implement theCharSequence interface.
Parameters:
beginIndex - the begin index, inclusive.
endIndex - the end index, exclusive.
Returns:
the specified subsequence.
Throws:
IndexOutOfBoundsException - ifbeginIndex orendIndex is negative, ifendIndex is greater thanlength(), or ifbeginIndex is greater thanendIndex
Since:
1.4

concat
```
public String concat(String str)
```
Concatenates the specified string to the end of this string.
If the length of the argument string is0, then thisString object is returned. Otherwise, aString object is returned that represents a character sequence that is the concatenation of the character sequence represented by thisString object and the character sequence represented by the argument string.
Examples:
```
 "cares".concat("s") returns "caress" "to".concat("get").concat("her") returns "together"
```
Parameters:
str - theString that is concatenated to the end of thisString.
Returns:
a string that represents the concatenation of this object's characters followed by the string argument's characters.

replace
```
public String replace(char oldChar,                      char newChar)
```
Returns a string resulting from replacing all occurrences ofoldChar in this string withnewChar.
If the characteroldChar does not occur in the character sequence represented by thisString object, then a reference to thisString object is returned. Otherwise, aString object is returned that represents a character sequence identical to the character sequence represented by thisString object, except that every occurrence ofoldChar is replaced by an occurrence ofnewChar.
Examples:
```
 "mesquite in your cellar".replace('e', 'o')         returns "mosquito in your collar" "the war of baronets".replace('r', 'y')         returns "the way of bayonets" "sparring with a purple porpoise".replace('p', 't')         returns "starring with a turtle tortoise" "JonL".replace('q', 'x') returns "JonL" (no change)
```
Parameters:
oldChar - the old character.
newChar - the new character.
Returns:
a string derived from this string by replacing every occurrence ofoldChar withnewChar.

matches
```
public boolean matches(String regex)
```
Tells whether or not this string matches the givenregular expression.
An invocation of this method of the formstr.matches(regex) yields exactly the same result as the expression
Pattern.matches(regex,str)
Parameters:
regex - the regular expression to which this string is to be matched
Returns:
true if, and only if, this string matches the given regular expression
Throws:
PatternSyntaxException - if the regular expression's syntax is invalid
Since:
1.4
See Also:
Pattern

contains
```
public boolean contains(CharSequence s)
```
Returns true if and only if this string contains the specified sequence of char values.
Parameters:
s - the sequence to search for
Returns:
true if this string containss, false otherwise
Since:
1.5

replaceFirst
```
public String replaceFirst(String regex,String replacement)
```
Replaces the first substring of this string that matches the givenregular expression with the given replacement.
An invocation of this method of the formstr.replaceFirst(regex,repl) yields exactly the same result as the expression
Pattern.compile(regex).matcher(str).replaceFirst(repl)
Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; seeMatcher.replaceFirst(java.lang.String). UseMatcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.
Parameters:
regex - the regular expression to which this string is to be matched
replacement - the string to be substituted for the first match
Returns:
The resultingString
Throws:
PatternSyntaxException - if the regular expression's syntax is invalid
Since:
1.4
See Also:
Pattern

replaceAll
```
public String replaceAll(String regex,String replacement)
```
Replaces each substring of this string that matches the givenregular expression with the given replacement.
An invocation of this method of the formstr.replaceAll(regex,repl) yields exactly the same result as the expression
Pattern.compile(regex).matcher(str).replaceAll(repl)
Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; seeMatcher.replaceAll. UseMatcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.
Parameters:
regex - the regular expression to which this string is to be matched
replacement - the string to be substituted for each match
Returns:
The resultingString
Throws:
PatternSyntaxException - if the regular expression's syntax is invalid
Since:
1.4
See Also:
Pattern

replace
```
public String replace(CharSequence target,CharSequence replacement)
```
Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. The replacement proceeds from the beginning of the string to the end, for example, replacing "aa" with "b" in the string "aaa" will result in "ba" rather than "ab".
Parameters:
target - The sequence of char values to be replaced
replacement - The replacement sequence of char values
Returns:
The resulting string
Since:
1.5

split
```
public String[] split(String regex,                      int limit)
```
Splits this string around matches of the givenregular expression.
The array returned by this method contains each substring of this string that is terminated by another substring that matches the given expression or is terminated by the end of the string. The substrings in the array are in the order in which they occur in this string. If the expression does not match any part of the input then the resulting array has just one element, namely this string.
When there is a positive-width match at the beginning of this string then an empty leading substring is included at the beginning of the resulting array. A zero-width match at the beginning however never produces such empty leading substring.
Thelimit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limitn is greater than zero then the pattern will be applied at mostn - 1 times, the array's length will be no greater thann, and the array's last entry will contain all input beyond the last matched delimiter. Ifn is non-positive then the pattern will be applied as many times as possible and the array can have any length. Ifn is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.
The string"boo:and:foo", for example, yields the following results with these parameters:
Regex Limit Result
: 2 { "boo", "and:foo" }
: 5 { "boo", "and", "foo" }
: -2 { "boo", "and", "foo" }
o 5 { "b", "", ":and:f", "", "" }
o -2 { "b", "", ":and:f", "", "" }
o 0 { "b", "", ":and:f" }
An invocation of this method of the formstr.split(regex, n) yields the same result as the expression
Pattern.compile(regex).split(str, n)
Parameters:
regex - the delimiting regular expression
limit - the result threshold, as described above
Returns:
the array of strings computed by splitting this string around matches of the given regular expression
Throws:
PatternSyntaxException - if the regular expression's syntax is invalid
Since:
1.4
See Also:
Pattern

Regex	Limit	Result
:	2	`{ "boo", "and:foo" }`
:	5	`{ "boo", "and", "foo" }`
:	-2	`{ "boo", "and", "foo" }`
o	5	`{ "b", "", ":and:f", "", "" }`
o	-2	`{ "b", "", ":and:f", "", "" }`
o	0	`{ "b", "", ":and:f" }`

split
```
public String[] split(String regex)
```
Splits this string around matches of the givenregular expression.
This method works as if by invoking the two-argumentsplit method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.
The string"boo:and:foo", for example, yields the following results with these expressions:
Regex Result
: { "boo", "and", "foo" }
o { "b", "", ":and:f" }
Parameters:
regex - the delimiting regular expression
Returns:
the array of strings computed by splitting this string around matches of the given regular expression
Throws:
PatternSyntaxException - if the regular expression's syntax is invalid
Since:
1.4
See Also:
Pattern

Regex	Result
:	`{ "boo", "and", "foo" }`
o	`{ "b", "", ":and:f" }`

join
```
public static String join(CharSequence delimiter,CharSequence... elements)
```
Returns a new String composed of copies of theCharSequence elements joined together with a copy of the specifieddelimiter.
For example,
```
     String message = String.join("-", "Java", "is", "cool");     // message returned is: "Java-is-cool"
```
Note that if an element is null, then"null" is added.
Parameters:
delimiter - the delimiter that separates each element
elements - the elements to join together.
Returns:
a newString that is composed of theelements separated by thedelimiter
Throws:
NullPointerException - Ifdelimiter orelements isnull
Since:
1.8
See Also:
StringJoiner

join
```
public static String join(CharSequence delimiter,Iterable<? extendsCharSequence> elements)
```
Returns a newString composed of copies of theCharSequence elements joined together with a copy of the specifieddelimiter.
For example,
```
     List<String> strings = new LinkedList<>();     strings.add("Java");strings.add("is");     strings.add("cool");     String message = String.join(" ", strings);     //message returned is: "Java is cool"     Set<String> strings = new LinkedHashSet<>();     strings.add("Java"); strings.add("is");     strings.add("very"); strings.add("cool");     String message = String.join("-", strings);     //message returned is: "Java-is-very-cool"
```
Note that if an individual element isnull, then"null" is added.
Parameters:
delimiter - a sequence of characters that is used to separate each of theelements in the resultingString
elements - anIterable that will have itselements joined together.
Returns:
a newString that is composed from theelements argument
Throws:
NullPointerException - Ifdelimiter orelements isnull
Since:
1.8
See Also:
join(CharSequence,CharSequence...),StringJoiner

toLowerCase

public String toLowerCase(Locale locale)

Converts all of the characters in thisString to lower case using the rules of the givenLocale. Case mapping is based on the Unicode Standard version specified by theCharacter class. Since case mappings are not always 1:1 char mappings, the resultingString may be a different length than the originalString.

Examples of lowercase mappings are in the following table:

Language Code of Locale	Upper Case	Lower Case	Description
tr (Turkish)	\u0130	\u0069	capital letter I with dot above -> small letter i
tr (Turkish)	\u0049	\u0131	capital letter I -> small letter dotless i
(all)	French Fries	french fries	lowercased all chars in String
(all)			lowercased all chars in String

Parameters:: locale - use the case transformation rules for this locale
Returns:: theString, converted to lowercase.
Since:: 1.1
See Also:: toLowerCase(),toUpperCase(),toUpperCase(Locale)

toLowerCase
```
public String toLowerCase()
```
Converts all of the characters in thisString to lower case using the rules of the default locale. This is equivalent to callingtoLowerCase(Locale.getDefault()).
Note: This method is locale sensitive, and may produce unexpected results if used for strings that are intended to be interpreted locale independently. Examples are programming language identifiers, protocol keys, and HTML tags. For instance,"TITLE".toLowerCase() in a Turkish locale returns"t\u0131tle", where '\u0131' is the LATIN SMALL LETTER DOTLESS I character. To obtain correct results for locale insensitive strings, usetoLowerCase(Locale.ROOT).
Returns:
theString, converted to lowercase.
See Also:
toLowerCase(Locale)

toUpperCase

public String toUpperCase(Locale locale)

Converts all of the characters in thisString to upper case using the rules of the givenLocale. Case mapping is based on the Unicode Standard version specified by theCharacter class. Since case mappings are not always 1:1 char mappings, the resultingString may be a different length than the originalString.

Examples of locale-sensitive and 1:M case mappings are in the following table.

Language Code of Locale	Lower Case	Upper Case	Description
tr (Turkish)	\u0069	\u0130	small letter i -> capital letter I with dot above
tr (Turkish)	\u0131	\u0049	small letter dotless i -> capital letter I
(all)	\u00df	\u0053 \u0053	small letter sharp s -> two letters: SS
(all)	Fahrvergnügen	FAHRVERGNÜGEN

Parameters:: locale - use the case transformation rules for this locale
Returns:: theString, converted to uppercase.
Since:: 1.1
See Also:: toUpperCase(),toLowerCase(),toLowerCase(Locale)

toUpperCase
```
public String toUpperCase()
```
Converts all of the characters in thisString to upper case using the rules of the default locale. This method is equivalent totoUpperCase(Locale.getDefault()).
Note: This method is locale sensitive, and may produce unexpected results if used for strings that are intended to be interpreted locale independently. Examples are programming language identifiers, protocol keys, and HTML tags. For instance,"title".toUpperCase() in a Turkish locale returns"T\u0130TLE", where '\u0130' is the LATIN CAPITAL LETTER I WITH DOT ABOVE character. To obtain correct results for locale insensitive strings, usetoUpperCase(Locale.ROOT).
Returns:
theString, converted to uppercase.
See Also:
toUpperCase(Locale)

trim
```
public String trim()
```
Returns a string whose value is this string, with any leading and trailing whitespace removed.
If thisString object represents an empty character sequence, or the first and last characters of character sequence represented by thisString object both have codes greater than'\u0020' (the space character), then a reference to thisString object is returned.
Otherwise, if there is no character with a code greater than'\u0020' in the string, then aString object representing an empty string is returned.
Otherwise, letk be the index of the first character in the string whose code is greater than'\u0020', and letm be the index of the last character in the string whose code is greater than'\u0020'. AString object is returned, representing the substring of this string that begins with the character at indexk and ends with the character at indexm-that is, the result ofthis.substring(k, m + 1).
This method may be used to trim whitespace (as defined above) from the beginning and end of a string.
Returns:
A string whose value is this string, with any leading and trailing white space removed, or this string if it has no leading or trailing white space.

toString
```
public String toString()
```
This object (which is already a string!) is itself returned.
Specified by:
toString in interface CharSequence
Overrides:
toString in class Object
Returns:
the string itself.

toCharArray
```
public char[] toCharArray()
```
Converts this string to a new character array.
Returns:
a newly allocated character array whose length is the length of this string and whose contents are initialized to contain the character sequence represented by this string.

format
```
public static String format(String format,Object... args)
```
Returns a formatted string using the specified format string and arguments.
The locale always used is the one returned byLocale.getDefault().
Parameters:
format - Aformat string
args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined byThe Java™ Virtual Machine Specification. The behaviour on anull argument depends on theconversion.
Returns:
A formatted string
Throws:
IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see theDetails section of the formatter class specification.
Since:
1.5
See Also:
Formatter

format
```
public static String format(Locale l,String format,Object... args)
```
Returns a formatted string using the specified locale, format string, and arguments.
Parameters:
l - Thelocale to apply during formatting. Ifl isnull then no localization is applied.
format - Aformat string
args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined byThe Java™ Virtual Machine Specification. The behaviour on anull argument depends on theconversion.
Returns:
A formatted string
Throws:
IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see theDetails section of the formatter class specification
Since:
1.5
See Also:
Formatter

valueOf
```
public static String valueOf(Object obj)
```
Returns the string representation of theObject argument.
Parameters:
obj - anObject.
Returns:
if the argument isnull, then a string equal to"null"; otherwise, the value ofobj.toString() is returned.
See Also:
Object.toString()

valueOf
```
public static String valueOf(char[] data)
```
Returns the string representation of thechar array argument. The contents of the character array are copied; subsequent modification of the character array does not affect the returned string.
Parameters:
data - the character array.
Returns:
aString that contains the characters of the character array.

valueOf
```
public static String valueOf(char[] data,                             int offset,                             int count)
```
Returns the string representation of a specific subarray of thechar array argument.
Theoffset argument is the index of the first character of the subarray. Thecount argument specifies the length of the subarray. The contents of the subarray are copied; subsequent modification of the character array does not affect the returned string.
Parameters:
data - the character array.
offset - initial offset of the subarray.
count - length of the subarray.
Returns:
aString that contains the characters of the specified subarray of the character array.
Throws:
IndexOutOfBoundsException - ifoffset is negative, orcount is negative, oroffset+count is larger thandata.length.

copyValueOf
```
public static String copyValueOf(char[] data,                                 int offset,                                 int count)
```
Equivalent tovalueOf(char[], int, int).
Parameters:
data - the character array.
offset - initial offset of the subarray.
count - length of the subarray.
Returns:
aString that contains the characters of the specified subarray of the character array.
Throws:
IndexOutOfBoundsException - ifoffset is negative, orcount is negative, oroffset+count is larger thandata.length.

copyValueOf
```
public static String copyValueOf(char[] data)
```
Equivalent tovalueOf(char[]).
Parameters:
data - the character array.
Returns:
aString that contains the characters of the character array.

valueOf
```
public static String valueOf(boolean b)
```
Returns the string representation of theboolean argument.
Parameters:
b - aboolean.
Returns:
if the argument istrue, a string equal to"true" is returned; otherwise, a string equal to"false" is returned.

valueOf
```
public static String valueOf(char c)
```
Returns the string representation of thechar argument.
Parameters:
c - achar.
Returns:
a string of length1 containing as its single character the argumentc.

valueOf
```
public static String valueOf(int i)
```
Returns the string representation of theint argument.
The representation is exactly the one returned by theInteger.toString method of one argument.
Parameters:
i - anint.
Returns:
a string representation of theint argument.
See Also:
Integer.toString(int, int)

valueOf
```
public static String valueOf(long l)
```
Returns the string representation of thelong argument.
The representation is exactly the one returned by theLong.toString method of one argument.
Parameters:
l - along.
Returns:
a string representation of thelong argument.
See Also:
Long.toString(long)

valueOf
```
public static String valueOf(float f)
```
Returns the string representation of thefloat argument.
The representation is exactly the one returned by theFloat.toString method of one argument.
Parameters:
f - afloat.
Returns:
a string representation of thefloat argument.
See Also:
Float.toString(float)

valueOf
```
public static String valueOf(double d)
```
Returns the string representation of thedouble argument.
The representation is exactly the one returned by theDouble.toString method of one argument.
Parameters:
d - adouble.
Returns:
a string representation of thedouble argument.
See Also:
Double.toString(double)

intern
```
public String intern()
```
Returns a canonical representation for the string object.
A pool of strings, initially empty, is maintained privately by the classString.
When the intern method is invoked, if the pool already contains a string equal to thisString object as determined by theequals(Object) method, then the string from the pool is returned. Otherwise, thisString object is added to the pool and a reference to thisString object is returned.
It follows that for any two stringss andt,s.intern() == t.intern() istrue if and only ifs.equals(t) istrue.
All literal strings and string-valued constant expressions are interned. String literals are defined in section 3.10.5 of theThe Java™ Language Specification.
Returns:
a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings.

Movatterモバイル変換

Class String

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.CharSequence

Field Detail

CASE_INSENSITIVE_ORDER

Constructor Detail

String

String

String

String

String

String

String

String

String

String

String

String

String

String

String

Method Detail

length

isEmpty

charAt

codePointAt

codePointBefore

codePointCount

offsetByCodePoints

getChars

getBytes

getBytes

getBytes

getBytes

equals

contentEquals

contentEquals

equalsIgnoreCase

compareTo

compareToIgnoreCase

regionMatches

regionMatches

startsWith

startsWith

endsWith

hashCode

indexOf

indexOf

lastIndexOf

lastIndexOf

indexOf

indexOf

lastIndexOf

lastIndexOf

substring

substring

subSequence

concat

replace

matches

contains

replaceFirst

replaceAll

replace

split

split

join

join

toLowerCase

toLowerCase

toUpperCase

toUpperCase

trim

toString

toCharArray

format