String
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 class String
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 relies heavily on the information provided by the Unicode Consortium's Unicode 3.0 specification. The specification's UnicodeData.txt and SpecialCasing.txt files are used extensively to provide case mapping.
The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuffer
class and its append
method. String conversions are implemented through the method toString
, defined by Object
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 a null argument to a constructor or method in this class will cause a NullPointerException to be thrown.
Field Detail |
private char[] value
private int offset
private int count
private int hash
private static final long serialVersionUID
private static final ObjectStreamField[] serialPersistentFields
TC_STRING
(utf String)
The String is written by method DataOutput.writeUTF
. A new handle is generated to refer to all future references to the string instance within the stream.public static final Comparator CASE_INSENSITIVE_ORDER
String
objects as by compareToIgnoreCase
. This comparator is serializable. Note that this Comparator does not take locale into account, and will result in an unsatisfactory ordering for certain locales. The java.text package provides Collators to allow locale-sensitive ordering.
Constructor Detail |
public String()
String
object so that it represents an empty character sequence. Note that use of this constructor is unnecessary since Strings are immutable.public String(String original)
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. Unless an explicit copy of original
is needed, use of this constructor is unnecessary since Strings are immutable.original
- a String
.public String(char[] value)
String
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.value
- the initial value of the string.public String(char[] value, int offset, int count)
String
that contains characters from a subarray of the character array argument. The offset
argument is the index of the first character of the subarray and the count
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.value
- array that is the source of characters.offset
- the initial offset.count
- the length.IndexOutOfBoundsException
- if the offset
and count
arguments index characters outside the bounds of the value
array.public String(byte[] ascii, int hibyte, int offset, int count)
String
constructors that take a charset name or that use the platform's default charset.String
constructed from a subarray of an array of 8-bit integer values. The offset
argument is the index of the first byte of the subarray, and the count
argument specifies the length of the subarray.
Each byte
in the subarray is converted to a char
as specified in the method above.
ascii
- the bytes to be converted to characters.hibyte
- the top 8 bits of each 16-bit Unicode character.offset
- the initial offset.count
- the length.IndexOutOfBoundsException
- if the offset
or count
argument is invalid.public String(byte[] ascii, int hibyte)
String
constructors that take a charset name or that use the platform's default charset.String
containing characters constructed from an array of 8-bit integer values. Each character cin the resulting string is constructed from the corresponding component b in the byte array such that: c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
ascii
- the bytes to be converted to characters.hibyte
- the top 8 bits of each 16-bit Unicode character.public String(byte[] bytes, int offset, int length, String charsetName)
The behavior of this constructor when the given bytes are not valid in the given charset is unspecified. The java.nio.charset.CharsetDecoder class should be used when more control over the decoding process is required.
bytes
- the bytes to be decoded into charactersoffset
- the index of the first byte to decodelength
- the number of bytes to decodecharsetName
- the name of a supported charset
UnsupportedEncodingException
- if the named charset is not supportedIndexOutOfBoundsException
- if the offset and length arguments index characters outside the bounds of the bytes arraypublic String(byte[] bytes, String charsetName)
The behavior of this constructor when the given bytes are not valid in the given charset is unspecified. The java.nio.charset.CharsetDecoder class should be used when more control over the decoding process is required.
bytes
- the bytes to be decoded into characterscharsetName
- the name of a supported charset
UnsupportedEncodingException
- If the named charset is not supportedpublic String(byte[] bytes, int offset, int length)
The behavior of this constructor when the given bytes are not valid in the default charset is unspecified. The java.nio.charset.CharsetDecoder class should be used when more control over the decoding process is required.
bytes
- the bytes to be decoded into charactersoffset
- the index of the first byte to decodelength
- the number of bytes to decodeIndexOutOfBoundsException
- if the offset
and the length
arguments index characters outside the bounds of the bytes
arraypublic String(byte[] bytes)
The behavior of this constructor when the given bytes are not valid in the default charset is unspecified. The java.nio.charset.CharsetDecoder class should be used when more control over the decoding process is required.
bytes
- the bytes to be decoded into characterspublic String(StringBuffer buffer)
buffer
- a StringBuffer
.Method Detail |
public int length()
public char charAt(int index)
0
to length() - 1
. The first character of the sequence is at index 0
, the next at index 1
, and so on, as for array indexing.index
- the index of the character.0
.IndexOutOfBoundsException
- if the index
argument is negative or not less than the length of this string.public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
The first character to be copied is at index srcBegin
; the last character to be copied is at index srcEnd-1
(thus the total number of characters to be copied is srcEnd-srcBegin
). The characters are copied into the subarray of dst
starting at index dstBegin
and ending at index:
dstbegin + (srcEnd-srcBegin) - 1
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.IndexOutOfBoundsException
- If any of the following is true: srcBegin
is negative. srcBegin
is greater than srcEnd
srcEnd
is greater than the length of this string dstBegin
is negative dstBegin+(srcEnd-srcBegin)
is larger than dst.length
public void getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)
getBytes()
method, which uses the platform's default charset. The first character to be copied is at index srcBegin
; the last character to be copied is at index srcEnd-1
. The total number of characters to be copied is srcEnd-srcBegin
. The characters, converted to bytes, are copied into the subarray of dst
starting at index dstBegin
and ending at index:
dstbegin + (srcEnd-srcBegin) - 1
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.IndexOutOfBoundsException
- if any of the following is true: srcBegin
is negative srcBegin
is greater than srcEnd
srcEnd
is greater than the length of this String dstBegin
is negative dstBegin+(srcEnd-srcBegin)
is larger than dst.length
public byte[] getBytes(String charsetName)
The behavior of this method when this string cannot be encoded in the given charset is unspecified. The java.nio.charset.CharsetEncoder class should be used when more control over the encoding process is required.
charsetName
- the name of a supported charset
UnsupportedEncodingException
- If the named charset is not supportedpublic byte[] getBytes()
The behavior of this method when this string cannot be encoded in the default charset is unspecified. The java.nio.charset.CharsetEncoder class should be used when more control over the encoding process is required.
public boolean equals(Object anObject)
true
if and only if the argument is not null
and is a String
object that represents the same sequence of characters as this object.anObject
- the object to compare this String
against.true
if the String
are equal; false
otherwise.public boolean contentEquals(StringBuffer sb)
sb
- the StringBuffer to compare to.public boolean equalsIgnoreCase(String anotherString)
String
to another String
, 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 characters c1
and c2
are considered the same, ignoring case if at least one of the following is true:
==
operator). anotherString
- the String
to compare this String
against.true
if the argument is not null
and the String
s are equal, ignoring case; false
otherwise.public int compareTo(String anotherString)
String
object is compared lexicographically to the character sequence represented by the argument string. The result is a negative integer if this String
object lexicographically precedes the argument string. The result is a positive integer if this String
object lexicographically follows the argument string. The result is zero if the strings are equal; compareTo
returns 0
exactly when the #equals(Object) method would return true
. 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, let k be the smallest such index; then the string whose character at position k 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 position k
in the two string -- that is, the value:
If there is no index position at which they differ, then the shorter string lexicographically precedes the longer string. In this case,this.charAt(k)-anotherString.charAt(k)
compareTo
returns the difference of the lengths of the strings -- that is, the value: this.length()-anotherString.length()
anotherString
- the String
to be compared.0
if the argument string is equal to this string; a value less than 0
if this string is lexicographically less than the string argument; and a value greater than 0
if this string is lexicographically greater than the string argument.public int compareTo(Object o)
compareTo(String)
. Otherwise, it throws a ClassCastException
(as Strings are comparable only to other Strings).o
- the Object
to be compared.0
if the argument is a string lexicographically equal to this string; a value less than 0
if the argument is a string lexicographically greater than this string; and a value greater than 0
if the argument is a string lexicographically less than this string.ClassCastException
- if the argument is not a String
.public int compareToIgnoreCase(String str)
compareTo
with normalized versions of the strings where case differences have been eliminated by calling Character.toLowerCase(Character.toUpperCase(character))
on each character. Note that this method does not take locale into account, and will result in an unsatisfactory ordering for certain locales. The java.text package provides collators to allow locale-sensitive ordering.
str
- the String
to be compared.public boolean regionMatches(int toffset, String other, int ooffset, int len)
A substring of this String object is compared to a substring of the argument other. The result is true if these substrings represent identical character sequences. The substring of this String object to be compared begins at index toffset and has length len. The substring of other to be compared begins at index ooffset and has length len. The result is false if and only if at least one of the following is true:
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.true
if the specified subregion of this string exactly matches the specified subregion of the string argument; false
otherwise.public boolean regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)
A substring of this String object is compared to a substring of the argument other. The result is true if these substrings represent character sequences that are the same, ignoring case if and only if ignoreCase is true. The substring of this String object to be compared begins at index toffset and has length len. The substring of other to be compared begins at index ooffset and has length len. The result is false if and only if at least one of the following is true:
this.charAt(toffset+k) != other.charAt(ooffset+k)
and:Character.toLowerCase(this.charAt(toffset+k)) != Character.toLowerCase(other.charAt(ooffset+k))
Character.toUpperCase(this.charAt(toffset+k)) != Character.toUpperCase(other.charAt(ooffset+k))
ignoreCase
- if true
, 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.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 the ignoreCase
argument.public boolean startsWith(String prefix, int toffset)
prefix
- the prefix.toffset
- where to begin looking in the string.true
if the character sequence represented by the argument is a prefix of the substring of this object starting at index toffset
; false
otherwise. The result is false
if toffset
is negative or greater than the length of this String
object; otherwise the result is the same as the result of the expression this.subString(toffset).startsWith(prefix)
public boolean startsWith(String prefix)
prefix
- the prefix.true
if the character sequence represented by the argument is a prefix of the character sequence represented by this string; false
otherwise. Note also that true
will be returned if the argument is an empty string or is equal to this String
object as determined by the #equals(Object) method.public boolean endsWith(String suffix)
suffix
- the suffix.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 be true
if the argument is the empty string or is equal to this String
object as determined by the #equals(Object) method.public int hashCode()
String
object is computed as usings[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
int
arithmetic, where s[i]
is the ith character of the string, n
is the length of the string, and ^
indicates exponentiation. (The hash value of the empty string is zero.)public int indexOf(int ch)
ch
occurs in the character sequence represented by this String
object, then the index of the first such occurrence is returned -- that is, the smallest value k such that: isthis.charAt(k) == ch
true
. If no such character occurs in this string, then -1
is returned.ch
- a character.-1
if the character does not occur.public int indexOf(int ch, int fromIndex)
If a character with value ch
occurs in the character sequence represented by this String
object at an index no smaller than fromIndex
, then the index of the first such occurrence is returned--that is, the smallest value k such that:
is true. If no such character occurs in this string at or after position(this.charAt(k) == ch) && (k >= fromIndex)
fromIndex
, then -1
is returned. There is no restriction on the value of fromIndex
. 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.
ch
- a character.fromIndex
- the index to start the search from.fromIndex
, or -1
if the character does not occur.public int lastIndexOf(int ch)
is true. The String is searched backwards starting at the last character.this.charAt(k) == ch
ch
- a character.-1
if the character does not occur.public int lastIndexOf(int ch, int fromIndex)
is true.this.charAt(k) == ch) && (k <= fromIndex)
ch
- a character.fromIndex
- the index to start the search from. There is no restriction on the value of fromIndex
. 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.fromIndex
, or -1
if the character does not occur before that point.public int indexOf(String str)
isthis.startsWith(str, k)
true
.str
- any string.-1
is returned.public int indexOf(String str, int fromIndex)
If no such value of k exists, then -1 is returned.k >= Math.min(fromIndex, str.length()) && this.startsWith(str, k)
str
- the substring for which to search.fromIndex
- the index from which to start the search.static int indexOf(char[] source, int sourceOffset, int sourceCount, char[] target, int targetOffset, int targetCount, int fromIndex)
source
- the characters being searched.sourceOffset
- offset of the source string.sourceCount
- count of the source string.target
- the characters being searched for.targetOffset
- offset of the target string.targetCount
- count of the target string.fromIndex
- the index to begin searching from.public int lastIndexOf(String str)
this.length()
. The returned index is the largest value k such that is true.this.startsWith(str, k)
str
- the substring to search for.-1
is returned.public int lastIndexOf(String str, int fromIndex)
If no such value of k exists, then -1 is returned.k <= Math.min(fromIndex, str.length()) && this.startsWith(str, k)
str
- the substring to search for.fromIndex
- the index to start the search from.static int lastIndexOf(char[] source, int sourceOffset, int sourceCount, char[] target, int targetOffset, int targetCount, int fromIndex)
source
- the characters being searched.sourceOffset
- offset of the source string.sourceCount
- count of the source string.target
- the characters being searched for.targetOffset
- offset of the target string.targetCount
- count of the target string.fromIndex
- the index to begin searching from.public String substring(int beginIndex)
Examples:
"unhappy".substring(2) returns "happy" "Harbison".substring(3) returns "bison" "emptiness".substring(9) returns "" (an empty string)
beginIndex
- the beginning index, inclusive.IndexOutOfBoundsException
- if beginIndex
is negative or larger than the length of this String
object.public String substring(int beginIndex, int endIndex)
beginIndex
and extends to the character at index endIndex - 1
. Thus the length of the substring is endIndex-beginIndex
. Examples:
"hamburger".substring(4, 8) returns "urge" "smiles".substring(1, 5) returns "mile"
beginIndex
- the beginning index, inclusive.endIndex
- the ending index, exclusive.IndexOutOfBoundsException
- if the beginIndex
is negative, or endIndex
is larger than the length of this String
object, or beginIndex
is larger than endIndex
.public CharSequence subSequence(int beginIndex, int endIndex)
An invocation of this method of the form
behaves in exactly the same way as the invocationstr.subSequence(begin, end)
This method is defined so that the String class can implement the CharSequence interface.str.substring(begin, end)
beginIndex
- the begin index, inclusive.endIndex
- the end index, exclusive.IndexOutOfBoundsException
- if beginIndex or endIndex are negative, if endIndex is greater than length(), or if beginIndex is greater than startIndexpublic String concat(String str)
If the length of the argument string is 0
, then this String
object is returned. Otherwise, a new String
object is created, representing a character sequence that is the concatenation of the character sequence represented by this String
object and the character sequence represented by the argument string.
Examples:
"cares".concat("s") returns "caress" "to".concat("get").concat("her") returns "together"
str
- the String
that is concatenated to the end of this String
.public String replace(char oldChar, char newChar)
oldChar
in this string with newChar
. If the character oldChar
does not occur in the character sequence represented by this String
object, then a reference to this String
object is returned. Otherwise, a new String
object is created that represents a character sequence identical to the character sequence represented by this String
object, except that every occurrence of oldChar
is replaced by an occurrence of newChar
.
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)
oldChar
- the old character.newChar
- the new character.oldChar
with newChar
.public boolean matches(String regex)
An invocation of this method of the form str.matches(regex) yields exactly the same result as the expression
java.util.regex.Pattern.matches(regex, str)
regex
- the regular expression to which this string is to be matchedPatternSyntaxException
- if the regular expression's syntax is invalidpublic String replaceFirst(String regex, String replacement)
An invocation of this method of the form str.replaceFirst(regex, repl) yields exactly the same result as the expression
java.util.regex.Pattern.compile(regex).matcher(str).replaceFirst(repl)
regex
- the regular expression to which this string is to be matchedPatternSyntaxException
- if the regular expression's syntax is invalidpublic String replaceAll(String regex, String replacement)
An invocation of this method of the form str.replaceAll(regex, repl) yields exactly the same result as the expression
java.util.regex.Pattern.compile(regex).matcher(str).replaceAll(repl)
regex
- the regular expression to which this string is to be matchedPatternSyntaxException
- if the regular expression's syntax is invalidpublic String[] split(String regex, int limit)
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.
The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n - 1 times, the array's length will be no greater than n, and the array's last entry will contain all input beyond the last matched delimiter. If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. If n 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 form str.split(regex, n) yields the same result as the expression
java.util.regex.Pattern.compile(regex).split(str, n)
regex
- the delimiting regular expressionlimit
- the result threshold, as described abovePatternSyntaxException
- if the regular expression's syntax is invalidpublic String[] split(String regex)
This method works as if by invoking the two-argument int) split 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" }
regex
- the delimiting regular expressionPatternSyntaxException
- if the regular expression's syntax is invalidpublic String toLowerCase(Locale locale)
String
to lower case using the rules of the given Locale
. Case mappings rely heavily on the Unicode specification's character data. Since case mappings are not always 1:1 char mappings, the resulting String
may be a different length than the original String
. 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 |
locale
- use the case transformation rules for this localeString
, converted to lowercase.public String toLowerCase()
String
to lower case using the rules of the default locale. This is equivalent to calling toLowerCase(Locale.getDefault())
. String
, converted to lowercase.public String toUpperCase(Locale locale)
String
to upper case using the rules of the given Locale
. Case mappings rely heavily on the Unicode specification's character data. Since case mappings are not always 1:1 char mappings, the resulting String
may be a different length than the original String
. 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 |
locale
- use the case transformation rules for this localeString
, converted to uppercase.public String toUpperCase()
String
to upper case using the rules of the default locale. This method is equivalent to toUpperCase(Locale.getDefault())
. String
, converted to uppercase.public String trim()
If this String
object represents an empty character sequence, or the first and last characters of character sequence represented by this String
object both have codes greater than '\u0020'
(the space character), then a reference to this String
object is returned.
Otherwise, if there is no character with a code greater than '\u0020'
in the string, then a new String
object representing an empty string is created and returned.
Otherwise, let k be the index of the first character in the string whose code is greater than '\u0020'
, and let m be the index of the last character in the string whose code is greater than '\u0020'
. A new String
object is created, representing the substring of this string that begins with the character at index k and ends with the character at index m-that is, the result of this.substring(k, m+1)
.
This method may be used to trim whitespace from the beginning and end of a string; in fact, it trims all ASCII control characters as well.
public String toString()
public char[] toCharArray()
public static String valueOf(Object obj)
Object
argument.obj
- an Object
.null
, then a string equal to "null"
; otherwise, the value of obj.toString()
is returned.public static String valueOf(char[] data)
char
array argument. The contents of the character array are copied; subsequent modification of the character array does not affect the newly created string.data
- a char
array.public static String valueOf(char[] data, int offset, int count)
char
array argument. The offset
argument is the index of the first character of the subarray. The count
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.
data
- the character array.offset
- the initial offset into the value of the String
.count
- the length of the value of the String
.IndexOutOfBoundsException
- if offset
is negative, or count
is negative, or offset+count
is larger than data.length
.public static String copyValueOf(char[] data, int offset, int count)
data
- the character array.offset
- initial offset of the subarray.count
- length of the subarray.String
that contains the characters of the specified subarray of the character array.public static String copyValueOf(char[] data)
data
- the character array.String
that contains the characters of the character array.public static String valueOf(boolean b)
boolean
argument.b
- a boolean
.true
, a string equal to "true"
is returned; otherwise, a string equal to "false"
is returned.public static String valueOf(char c)
char
argument.c
- a char
.1
containing as its single character the argument c
.public static String valueOf(int i)
int
argument. The representation is exactly the one returned by the Integer.toString
method of one argument.
i
- an int
.int
argument.public static String valueOf(long l)
long
argument. The representation is exactly the one returned by the Long.toString
method of one argument.
l
- a long
.long
argument.public static String valueOf(float f)
float
argument. The representation is exactly the one returned by the Float.toString
method of one argument.
f
- a float
.float
argument.public static String valueOf(double d)
double
argument. The representation is exactly the one returned by the Double.toString
method of one argument.
d
- a double
.double
argument.public native String intern()
A pool of strings, initially empty, is maintained privately by the class String
.
When the intern method is invoked, if the pool already contains a string equal to this String
object as determined by the #equals(Object) method, then the string from the pool is returned. Otherwise, this String
object is added to the pool and a reference to this String
object is returned.
It follows that for any two strings s
and t
, s.intern() == t.intern()
is true
if and only if s.equals(t)
is true
.
All literal strings and string-valued constant expressions are interned. String literals are defined in §3.10.5 of the Java Language Specification