String
public
final
class
String
extends Object
implements
Serializable,
Comparable<String>,
CharSequence
java.lang.Object | |
↳ | java.lang.String |
The 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 is based on the Unicode Standard version
specified by the Character
class.
The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. For additional information on string concatenation and conversion, see 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.
A String
represents a string in the UTF-16 format
in which supplementary characters are represented by surrogate
pairs (see the section Unicode
Character Representations in the Character
class for
more information).
Index values refer to char
code units, so a supplementary
character uses two positions in a String
.
The String
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).
Unless otherwise noted, methods for comparing Strings do not take locale
into account. The Collator
class provides methods for
finer-grain, locale-sensitive String comparison.
Summary
Fields | |
---|---|
public
static
final
Comparator<String> |
CASE_INSENSITIVE_ORDER
A Comparator that orders |
Public constructors | |
---|---|
String()
Initializes a newly created |
|
String(String original)
Initializes a newly created |
|
String(char[] value)
Allocates a new |
|
String(char[] value, int offset, int count)
Allocates a new |
|
String(int[] codePoints, int offset, int count)
Allocates a new |
|
String(byte[] ascii, int hibyte, int offset, int count)
This constructor is 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(byte[] ascii, int hibyte)
This constructor is 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(byte[] bytes, int offset, int length, String charsetName)
|
|
String(byte[] bytes, int offset, int length, Charset charset)
Constructs a new |
|
String(byte[] bytes, String charsetName)
Constructs a new |
|
String(byte[] bytes, Charset charset)
Constructs a new |
|
String(byte[] bytes, int offset, int length)
Constructs a new |
|
String(byte[] bytes)
Constructs a new |
|
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. |
Public methods | |
---|---|
char
|
charAt(int index)
Returns the |
IntStream
|
chars()
Returns a stream of |
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 |
IntStream
|
codePoints()
Returns a stream of code point values from this sequence. |
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(StringBuffer sb)
Compares this string to the specified |
boolean
|
contentEquals(CharSequence cs)
Compares this string to the specified |
static
String
|
copyValueOf(char[] data, int offset, int count)
Equivalent to |
static
String
|
copyValueOf(char[] data)
Equivalent to |
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 |
static
String
|
format(String format, Object... args)
Returns a formatted string using the specified format string and arguments. |
static
String
|
format(Locale l, String format, Object... args)
Returns a formatted string using the specified locale, format string, and arguments. |
String
|
formatted(Object... args)
Formats using this string as the format string, and the supplied arguments. |
byte[]
|
getBytes(String charsetName)
Encodes this |
byte[]
|
getBytes()
Encodes this |
byte[]
|
getBytes(Charset charset)
Encodes this |
void
|
getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)
This method was deprecated
in API level 15.
This method does not properly convert characters into
bytes. As of JDK 1.1, the preferred way to do this is via the
|
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. |
String
|
indent(int n)
Adjusts the indentation of each line of this string based on the value of
|
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(int ch)
Returns the index within this string of the first occurrence of the specified character. |
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
|
isBlank()
Returns |
boolean
|
isEmpty()
Returns |
static
String
|
join(CharSequence delimiter, CharSequence... elements)
Returns a new String composed of copies of the
|
static
String
|
join(CharSequence delimiter, Iterable<? extends CharSequence> elements)
Returns a new |
int
|
lastIndexOf(int ch)
Returns the index within this string of the last occurrence of the specified character. |
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
|
lastIndexOf(String str)
Returns the index within this string of the last occurrence of the specified substring. |
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
|
length()
Returns the length of this string. |
Stream<String>
|
lines()
Returns a stream of lines extracted from this string, separated by line terminators. |
boolean
|
matches(String regex)
Tells whether or not this string matches the given regular expression. |
int
|
offsetByCodePoints(int index, int codePointOffset)
Returns the index within this |
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
|
repeat(int count)
Returns a string whose value is the concatenation of this
string repeated |
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
|
replace(char oldChar, char newChar)
Returns a string resulting from replacing all occurrences of
|
String
|
replaceAll(String regex, String replacement)
Replaces each substring of this string that matches the given regular expression with the given replacement. |
String
|
replaceFirst(String regex, String replacement)
Replaces the first substring of this string that matches the given regular expression with the given replacement. |
String[]
|
split(String regex, int limit)
Splits this string around matches of the given regular expression. |
String[]
|
split(String regex)
Splits this string around matches of the given regular expression. |
boolean
|
startsWith(String prefix)
Tests if this string starts with the specified prefix. |
boolean
|
startsWith(String prefix, int toffset)
Tests if the substring of this string beginning at the specified index starts with the specified prefix. |
String
|
strip()
Returns a string whose value is this string, with all leading
and trailing |
String
|
stripIndent()
Returns a string whose value is this string, with incidental white space removed from the beginning and end of every line. |
String
|
stripLeading()
Returns a string whose value is this string, with all leading
|
String
|
stripTrailing()
Returns a string whose value is this string, with all trailing
|
CharSequence
|
subSequence(int beginIndex, int endIndex)
Returns a character sequence that is a subsequence of this sequence. |
String
|
substring(int beginIndex, int endIndex)
Returns a string that is a substring of this string. |
String
|
substring(int beginIndex)
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
|
toLowerCase(Locale locale)
Converts all of the characters in this |
String
|
toString()
This object (which is already a string!) is itself returned. |
String
|
toUpperCase(Locale locale)
Converts all of the characters in this |
String
|
toUpperCase()
Converts all of the characters in this |
<R>
R
|
transform(Function<? super String, ? extends R> f)
This method allows the application of a function to |
String
|
translateEscapes()
Returns a string whose value is this string, with escape sequences translated as if in a string literal. |
String
|
trim()
Returns a string whose value is this string, with all leading
and trailing space removed, where space is defined
as any character whose codepoint is less than or equal to
|
static
String
|
valueOf(boolean b)
Returns the string representation of the |
static
String
|
valueOf(double d)
Returns the string representation of the |
static
String
|
valueOf(char[] data, int offset, int count)
Returns the string representation of a specific subarray of the
|
static
String
|
valueOf(float f)
Returns the string representation of the |
static
String
|
valueOf(int i)
Returns the string representation of the |
static
String
|
valueOf(char c)
Returns the string representation of the |
static
String
|
valueOf(long l)
Returns the string representation of the |
static
String
|
valueOf(Object obj)
Returns the string representation of the |
static
String
|
valueOf(char[] data)
Returns the string representation of the |
Inherited methods | |
---|---|
Fields
CASE_INSENSITIVE_ORDER
public static final Comparator<String> CASE_INSENSITIVE_ORDER
A Comparator that orders 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 Collator
class provides locale-sensitive comparison.
See also:
Public constructors
String
public String ()
Initializes a newly created String
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 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. Unless an
explicit copy of original
is needed, use of this constructor is
unnecessary since Strings are immutable.
Parameters | |
---|---|
original |
String : A String |
String
public String (char[] value)
Allocates a new 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.
Parameters | |
---|---|
value |
char : The initial value of the string |
String
public String (char[] value, int offset, int count)
Allocates a new 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.
Parameters | |
---|---|
value |
char : Array that is the source of characters |
offset |
int : The initial offset |
count |
int : The length |
Throws | |
---|---|
IndexOutOfBoundsException |
If offset is negative, count is negative, or
offset is greater than value.length - count |
String
public String (int[] codePoints, int offset, int count)
Allocates a new String
that contains characters from a subarray
of the Unicode code point array
argument. The offset
argument is the index of the first code
point of the subarray and the count
argument specifies the
length of the subarray. The contents of the subarray are converted to
char
s; subsequent modification of the int
array does not
affect the newly created string.
Parameters | |
---|---|
codePoints |
int : Array that is the source of Unicode code points |
offset |
int : The initial offset |
count |
int : The length |
Throws | |
---|---|
IllegalArgumentException |
If any invalid Unicode code point is found in codePoints |
IndexOutOfBoundsException |
If offset is negative, count is negative, or
offset is greater than codePoints.length - count |
String
public String (byte[] ascii, int hibyte, int offset, int count)
This constructor is 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.
Allocates a new 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 String(byte[],int)
constructor.
Parameters | |
---|---|
ascii |
byte : The bytes to be converted to characters |
hibyte |
int : The top 8 bits of each 16-bit Unicode code unit |
offset |
int : The initial offset |
count |
int : The length |
Throws | |
---|---|
IndexOutOfBoundsException |
If offset is negative, count is negative, or
offset is greater than ascii.length - count |
String
public String (byte[] ascii, int hibyte)
This constructor is 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.
Allocates a new String
containing characters constructed from
an array of 8-bit integer values. Each character c in the
resulting string is constructed from the corresponding component
b in the byte array such that:
c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
Parameters | |
---|---|
ascii |
byte : The bytes to be converted to characters |
hibyte |
int : The top 8 bits of each 16-bit Unicode code unit |
String
public String (byte[] bytes, int offset, int length, String charsetName)
Parameters | |
---|---|
bytes |
byte |
offset |
int |
length |
int |
charsetName |
String |
Throws | |
---|---|
UnsupportedEncodingException |
String
public String (byte[] bytes, int offset, int length, Charset charset)
Constructs a new String
by decoding the specified subarray of
bytes using the specified charset.
The length of the new String
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. The CharsetDecoder
class should be used when more control
over the decoding process is required.
Parameters | |
---|---|
bytes |
byte : The bytes to be decoded into characters |
offset |
int : The index of the first byte to decode |
length |
int : The number of bytes to decode |
charset |
Charset : The charset to be used to
decode the bytes |
Throws | |
---|---|
IndexOutOfBoundsException |
If offset is negative, length is negative, or
offset is greater than bytes.length - length |
String
public String (byte[] bytes, String charsetName)
Constructs a new String
by decoding the specified array of bytes
using the specified charset. The
length of the new String
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. The CharsetDecoder
class should be used when more control
over the decoding process is required.
Parameters | |
---|---|
bytes |
byte : The bytes to be decoded into characters |
charsetName |
String : The name of a supported charset |
Throws | |
---|---|
UnsupportedEncodingException |
If the named charset is not supported |
String
public String (byte[] bytes, Charset charset)
Constructs a new String
by decoding the specified array of
bytes using the specified charset.
The length of the new String
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. The CharsetDecoder
class should be used when more control
over the decoding process is required.
Parameters | |
---|---|
bytes |
byte : The bytes to be decoded into characters |
charset |
Charset : The charset to be used to
decode the bytes |
String
public String (byte[] bytes, int offset, int length)
Constructs a new String
by decoding the specified subarray of
bytes using the platform's default charset. The length of the new
String
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. The CharsetDecoder
class should be used when more control
over the decoding process is required.
Parameters | |
---|---|
bytes |
byte : The bytes to be decoded into characters |
offset |
int : The index of the first byte to decode |
length |
int : The number of bytes to decode |
Throws | |
---|---|
IndexOutOfBoundsException |
If offset is negative, length is negative, or
offset is greater than bytes.length - length |
String
public String (byte[] bytes)
Constructs a new String
by decoding the specified array of bytes
using the platform's default charset. The length of the new String
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. The CharsetDecoder
class should be used when more control
over the decoding process is required.
Parameters | |
---|---|
bytes |
byte : The bytes to be decoded into characters |
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 |
StringBuffer : A StringBuffer |
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 to StringBuilder
. Obtaining a string from a string builder via the toString
method is likely to run faster and is generally preferred.
Parameters | |
---|---|
builder |
StringBuilder : A StringBuilder |
Public methods
charAt
public char charAt (int index)
Returns the char
value at the
specified index. An index ranges from 0
to
length() - 1
. The first char
value of the sequence
is at index 0
, the next at index 1
,
and so on, as for array indexing.
If the char
value specified by the index is a
surrogate, the surrogate
value is returned.
Parameters | |
---|---|
index |
int : the index of the char value. |
Returns | |
---|---|
char |
the char value at the specified index of this string.
The first char value is at index 0 . |
Throws | |
---|---|
IndexOutOfBoundsException |
if the index
argument is negative or not less than the length of this
string. |
chars
public IntStream chars ()
Returns a stream of int
zero-extending the char
values
from this sequence. Any char which maps to a surrogate code
point is passed through uninterpreted.
Returns | |
---|---|
IntStream |
an IntStream of char values from this sequence |
codePointAt
public int codePointAt (int index)
Returns the character (Unicode code point) at the specified
index. The index refers to char
values
(Unicode code units) and ranges from 0
to
length()
- 1
.
If the char
value specified at the given index
is in the high-surrogate range, the following index is less
than the length of this String
, and the
char
value at the following index is in the
low-surrogate range, then the supplementary code point
corresponding to this surrogate pair is returned. Otherwise,
the char
value at the given index is returned.
Parameters | |
---|---|
index |
int : the index to the char values |
Returns | |
---|---|
int |
the code point value of the character at the
index |
Throws | |
---|---|
IndexOutOfBoundsException |
if the index
argument is negative or not less than the length of this
string. |
codePointBefore
public int codePointBefore (int index)
Returns the character (Unicode code point) before the specified
index. The index refers to char
values
(Unicode code units) and ranges from 1
to length
.
If the char
value at (index - 1)
is in the low-surrogate range, (index - 2)
is not
negative, and the char
value at (index -
2)
is in the high-surrogate range, then the
supplementary code point value of the surrogate pair is
returned. If the char
value at index -
1
is an unpaired low-surrogate or a high-surrogate, the
surrogate value is returned.
Parameters | |
---|---|
index |
int : the index following the code point that should be returned |
Returns | |
---|---|
int |
the Unicode code point value before the given index. |
Throws | |
---|---|
IndexOutOfBoundsException |
if the index
argument is less than 1 or greater than the length
of this string. |
codePointCount
public int codePointCount (int beginIndex, int endIndex)
Returns the number of Unicode code points in the specified text
range of this String
. The text range begins at the
specified beginIndex
and extends to the
char
at index endIndex - 1
. Thus the
length (in char
s) of the text range is
endIndex-beginIndex
. Unpaired surrogates within
the text range count as one code point each.
Parameters | |
---|---|
beginIndex |
int : the index to the first char of
the text range. |
endIndex |
int : the index after the last char of
the text range. |
Returns | |
---|---|
int |
the number of Unicode code points in the specified text range |
Throws | |
---|---|
IndexOutOfBoundsException |
if the
beginIndex is negative, or endIndex
is larger than the length of this String , or
beginIndex is larger than endIndex . |
codePoints
public IntStream codePoints ()
Returns a stream of code point values from this sequence. Any surrogate
pairs encountered in the sequence are combined as if by Character.toCodePoint and the result is passed
to the stream. Any other code units, including ordinary BMP characters,
unpaired surrogates, and undefined code units, are zero-extended to
int
values which are then passed to the stream.
Returns | |
---|---|
IntStream |
an IntStream of Unicode code points from this sequence |
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 this
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(java.lang.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()
For finer-grained String comparison, refer to
Collator
.
Parameters | |
---|---|
anotherString |
String : the String to be compared. |
Returns | |
---|---|
int |
the value 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. |
compareToIgnoreCase
public int compareToIgnoreCase (String str)
Compares two strings lexicographically, ignoring case
differences. This method returns an integer whose sign is that of
calling 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 Collator
class provides locale-sensitive comparison.
Parameters | |
---|---|
str |
String : the String to be compared. |
Returns | |
---|---|
int |
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. |
See also:
concat
public String concat (String str)
Concatenates the specified string to the end of this string.
If the length of the argument string is 0
, then this
String
object is returned. Otherwise, a
String
object is returned that represents 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"
Parameters | |
---|---|
str |
String : the String that is concatenated to the end
of this String . |
Returns | |
---|---|
String |
a string that represents the concatenation of this object's characters followed by the string argument's characters. |
contains
public boolean contains (CharSequence s)
Returns true if and only if this string contains the specified sequence of char values.
Parameters | |
---|---|
s |
CharSequence : the sequence to search for |
Returns | |
---|---|
boolean |
true if this string contains s , false otherwise |
contentEquals
public boolean contentEquals (StringBuffer sb)
Compares this string to the specified StringBuffer
. The result
is true
if and only if this String
represents the same
sequence of characters as the specified StringBuffer
. This method
synchronizes on the StringBuffer
.
For finer-grained String comparison, refer to
Collator
.
Parameters | |
---|---|
sb |
StringBuffer : The StringBuffer to compare this String against |
Returns | |
---|---|
boolean |
true if this String represents the same
sequence of characters as the specified StringBuffer ,
false otherwise |
contentEquals
public boolean contentEquals (CharSequence cs)
Compares this string to the specified CharSequence
. The
result is true
if and only if this String
represents the
same sequence of char values as the specified sequence. Note that if the
CharSequence
is a StringBuffer
then the method
synchronizes on it.
For finer-grained String comparison, refer to
Collator
.
Parameters | |
---|---|
cs |
CharSequence : The sequence to compare this String against |
Returns | |
---|---|
boolean |
true if this String represents the same
sequence of char values as the specified sequence, false otherwise |
copyValueOf
public static String copyValueOf (char[] data, int offset, int count)
Equivalent to valueOf(char[], int, int)
.
Parameters | |
---|---|
data |
char : the character array. |
offset |
int : initial offset of the subarray. |
count |
int : length of the subarray. |
Returns | |
---|---|
String |
a String that contains the characters of the
specified subarray of the character array. |
Throws | |
---|---|
IndexOutOfBoundsException |
if offset is
negative, or count is negative, or
offset+count is larger than
data.length . |
copyValueOf
public static String copyValueOf (char[] data)
Equivalent to valueOf(char[])
.
Parameters | |
---|---|
data |
char : the character array. |
Returns | |
---|---|
String |
a String that contains the characters of the
character array. |
endsWith
public boolean endsWith (String suffix)
Tests if this string ends with the specified suffix.
Parameters | |
---|---|
suffix |
String : the suffix. |
Returns | |
---|---|
boolean |
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(java.lang.Object) method. |
equals
public boolean equals (Object anObject)
Compares this string to the specified object. The result is 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.
For finer-grained String comparison, refer to
Collator
.
Parameters | |
---|---|
anObject |
Object : The object to compare this String against |
Returns | |
---|---|
boolean |
true if the given object represents a String
equivalent to this string, false otherwise |
equalsIgnoreCase
public boolean equalsIgnoreCase (String anotherString)
Compares this 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:
- The two characters are the same (as compared by the
==
operator) - Calling
Character.toLowerCase(Character.toUpperCase(char))
on each character produces the same result
Note that this method does not take locale into account, and
will result in unsatisfactory results for certain locales. The
Collator
class provides locale-sensitive comparison.
Parameters | |
---|---|
anotherString |
String : The String to compare this String against |
Returns | |
---|---|
boolean |
true if the argument is not null and it
represents an equivalent String ignoring case; false otherwise |
See also:
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 by Locale.getDefault(Locale.Category)
with
FORMAT
category specified.
Parameters | |
---|---|
format |
String : A format string |
args |
Object : 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 by
The Java™ Virtual Machine Specification.
The behaviour on a
null argument depends on the conversion. |
Returns | |
---|---|
String |
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 the Details section of the formatter class specification. |
See also:
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 |
Locale : The locale to apply during
formatting. If l is null then no localization
is applied. |
format |
String : A format string |
args |
Object : 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 by
The Java™ Virtual Machine Specification.
The behaviour on a
null argument depends on the
conversion. |
Returns | |
---|---|
String |
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 the Details section of the formatter class specification |
See also:
formatted
public String formatted (Object... args)
Formats using this string as the format string, and the supplied arguments.
Implementation Requirements:
- This method is equivalent to
String.format(this, args)
.
Parameters | |
---|---|
args |
Object : Arguments referenced by the format specifiers in this string. |
Returns | |
---|---|
String |
A formatted string |
See also:
getBytes
public byte[] getBytes (String charsetName)
Encodes this String
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. The CharsetEncoder
class should be used when more control
over the encoding process is required.
Parameters | |
---|---|
charsetName |
String : The name of a supported charset |
Returns | |
---|---|
byte[] |
The resultant byte array |
Throws | |
---|---|
UnsupportedEncodingException |
If the named charset is not supported |
getBytes
public byte[] getBytes ()
Encodes this String
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. The CharsetEncoder
class should be used when more control
over the encoding process is required.
Returns | |
---|---|
byte[] |
The resultant byte array |
getBytes
public byte[] getBytes (Charset charset)
Encodes this String
into a sequence of bytes using the given
charset, 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. The
CharsetEncoder
class should be used when more
control over the encoding process is required.
Parameters | |
---|---|
charset |
Charset : The Charset to be used to encode
the String |
Returns | |
---|---|
byte[] |
The resultant byte array |
getBytes
public void getBytes (int srcBegin, int srcEnd, byte[] dst, int dstBegin)
This method was deprecated
in API level 15.
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.
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 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
Parameters | |
---|---|
srcBegin |
int : Index of the first character in the string to copy |
srcEnd |
int : Index after the last character in the string to copy |
dst |
byte : The destination array |
dstBegin |
int : The start offset in the destination array |
Throws | |
---|---|
IndexOutOfBoundsException |
If any of the following is true:
|
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 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
Parameters | |
---|---|
srcBegin |
int : index of the first character in the string
to copy. |
srcEnd |
int : index after the last character in the string
to copy. |
dst |
char : the destination array. |
dstBegin |
int : the start offset in the destination array. |
Throws | |
---|---|
IndexOutOfBoundsException |
If any of the following
is true:
|
hashCode
public int hashCode ()
Returns a hash code for this string. The hash code for a
String
object is computed as
using s[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.)
Returns | |
---|---|
int |
a hash code value for this object. |
indent
public String indent (int n)
Adjusts the indentation of each line of this string based on the value of
n
, and normalizes line termination characters.
This string is conceptually separated into lines using
String#lines()
. Each line is then adjusted as described below
and then suffixed with a line feed "\n"
(U+000A). The resulting
lines are then concatenated and returned.
If n > 0
then n
spaces (U+0020) are inserted at the
beginning of each line.
If n < 0
then up to n
white space characters are removed
from the beginning of each line. If a given line does not contain
sufficient white space then all leading
white space characters are removed.
Each white space character is treated as a single character. In
particular, the tab character "\t"
(U+0009) is considered a
single character; it is not expanded.
If n == 0
then the line remains unchanged. However, line
terminators are still normalized.
Parameters | |
---|---|
n |
int : number of leading
white space characters
to add or remove |
Returns | |
---|---|
String |
string with indentation adjusted and line endings normalized |
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 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. For values
of ch
in the range from 0 to 0xFFFF (inclusive),
this is the smallest value k such that:
is true. For other values of (this.charAt(k) == ch)&&
(k >= fromIndex)
ch
, it is the
smallest value k such that:
is true. In either case, if no such character occurs in this string at or after position (this.codePointAt(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.
All indices are specified in char
values
(Unicode code units).
Parameters | |
---|---|
ch |
int : a character (Unicode code point). |
fromIndex |
int : the index to start the search from. |
Returns | |
---|---|
int |
the index of the first occurrence of the character in the
character sequence represented by this object that is greater
than or equal to fromIndex , or -1
if the character does not occur. |
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 value k
for which:
this.startsWith(str, k)
k
exists, then -1
is returned.
Parameters | |
---|---|
str |
String : the substring to search for. |
Returns | |
---|---|
int |
the index of the first occurrence of the specified substring,
or -1 if there is no such occurrence. |
indexOf
public int indexOf (int ch)
Returns the index within this string of the first occurrence of
the specified character. If a character with value
ch
occurs in the character sequence represented by
this String
object, then the index (in Unicode
code units) of the first such occurrence is returned. For
values of ch
in the range from 0 to 0xFFFF
(inclusive), this is the smallest value k such that:
is true. For other values of this.charAt(k) == ch
ch
, it is the
smallest value k such that:
is true. In either case, if no such character occurs in this string, then this.codePointAt(k) == ch
-1
is returned.
Parameters | |
---|---|
ch |
int : a character (Unicode code point). |
Returns | |
---|---|
int |
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 (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 value k
for which:
k >= Math.min(fromIndex, this.length()) &&
this.startsWith(str, k)
k
exists, then -1
is returned.
Parameters | |
---|---|
str |
String : the substring to search for. |
fromIndex |
int : the index from which to start the search. |
Returns | |
---|---|
int |
the index of the first occurrence of the specified substring,
starting at the specified index,
or -1 if there is no such occurrence. |
intern
public String intern ()
Returns a canonical representation for the string object.
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(java.lang.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 section 3.10.5 of the The Java™ Language Specification.
Returns | |
---|---|
String |
a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings. |
isBlank
public boolean isBlank ()
Returns true
if the string is empty or contains only
white space
codepoints,
otherwise false
.
Returns | |
---|---|
boolean |
true if the string is empty or contains only
white space codepoints,
otherwise false |
See also:
isEmpty
public boolean isEmpty ()
Returns true
if, and only if, length()
is 0
.
Returns | |
---|---|
boolean |
true if length() is 0 , otherwise
false |
join
public static String 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
.
For example,Note that if an element is null, thenString message = String.join("-", "Java", "is", "cool"); // message returned is: "Java-is-cool"
"null"
is added.
Parameters | |
---|---|
delimiter |
CharSequence : the delimiter that separates each element |
elements |
CharSequence : the elements to join together. |
Returns | |
---|---|
String |
a new String that is composed of the elements
separated by the delimiter |
Throws | |
---|---|
NullPointerException |
If delimiter or elements
is null |
See also:
join
public static String join (CharSequence delimiter, Iterable<? extends CharSequence> elements)
Returns a new String
composed of copies of the
CharSequence elements
joined together with a copy of the
specified delimiter
.
For example,Note that if an individual element isList<String> strings = List.of("Java", "is", "cool"); String message = String.join(" ", strings); //message returned is: "Java is cool" Set<String> strings = new LinkedHashSet<>(List.of("Java", "is", "very", "cool")); String message = String.join("-", strings); //message returned is: "Java-is-very-cool"
null
, then "null"
is added.
Parameters | |
---|---|
delimiter |
CharSequence : a sequence of characters that is used to separate each
of the elements in the resulting String |
elements |
Iterable : an Iterable that will have its elements
joined together. |
Returns | |
---|---|
String |
a new String that is composed from the elements
argument |
Throws | |
---|---|
NullPointerException |
If delimiter or elements
is null |
lastIndexOf
public int lastIndexOf (int ch)
Returns the index within this string of the last occurrence of
the specified character. For values of ch
in the
range from 0 to 0xFFFF (inclusive), the index (in Unicode code
units) returned is the largest value k such that:
is true. For other values of this.charAt(k) == ch
ch
, it is the
largest value k such that:
is true. In either case, if no such character occurs in this string, then this.codePointAt(k) == ch
-1
is returned. The
String
is searched backwards starting at the last
character.
Parameters | |
---|---|
ch |
int : a character (Unicode code point). |
Returns | |
---|---|
int |
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 (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 value k
for which:
k <= Math.min(fromIndex, this.length()) &&
this.startsWith(str, k)
k
exists, then -1
is returned.
Parameters | |
---|---|
str |
String : the substring to search for. |
fromIndex |
int : the index to start the search from. |
Returns | |
---|---|
int |
the index of the last occurrence of the specified substring,
searching backward from 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 value this.length()
.
The returned index is the largest value k
for which:
this.startsWith(str, k)
k
exists, then -1
is returned.
Parameters | |
---|---|
str |
String : the substring to search for. |
Returns | |
---|---|
int |
the index of the last occurrence of the specified substring,
or -1 if there is no such occurrence. |
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 of ch
in the range
from 0 to 0xFFFF (inclusive), the index returned is the largest
value k such that:
is true. For other values of (this.charAt(k) == ch)&&
(k <= fromIndex)
ch
, it is the
largest value k such that:
is true. In either case, if no such character occurs in this string at or before position (this.codePointAt(k) == ch)&&
(k <= fromIndex)
fromIndex
, then
-1
is returned.
All indices are specified in char
values
(Unicode code units).
Parameters | |
---|---|
ch |
int : a character (Unicode code point). |
fromIndex |
int : 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. |
Returns | |
---|---|
int |
the index of the last occurrence of the character in the
character sequence represented by this object that is less
than or equal to fromIndex , or -1
if the character does not occur before that point. |
length
public int length ()
Returns the length of this string. The length is equal to the number of Unicode code units in the string.
Returns | |
---|---|
int |
the length of the sequence of characters represented by this object. |
lines
public Stream<String> lines ()
Returns a stream of lines extracted from this string, separated by line terminators.
A line terminator is one of the following:
a line feed character "\n"
(U+000A),
a carriage return character "\r"
(U+000D),
or a carriage return followed immediately by a line feed
"\r\n"
(U+000D U+000A).
A line is either a sequence of zero or more characters followed by a line terminator, or it is a sequence of one or more characters followed by the end of the string. A line does not include the line terminator.
The stream returned by this method contains the lines from this string in the order in which they occur.
API Note:
- This definition of line implies that an empty string has zero lines and that there is no empty line following a line terminator at the end of a string.
Implementation Note:
- This method provides better performance than split("\R") by supplying elements lazily and by faster search of new line terminators.
Returns | |
---|---|
Stream<String> |
the stream of lines extracted from this string |
matches
public boolean matches (String regex)
Tells whether or not this string matches the given regular expression.
An invocation of this method of the form
str.matches(
regex)
yields exactly the
same result as the expression
Pattern
.matches(regex, str)
Parameters | |
---|---|
regex |
String : the regular expression to which this string is to be matched |
Returns | |
---|---|
boolean |
true if, and only if, this string matches the
given regular expression |
Throws | |
---|---|
PatternSyntaxException |
if the regular expression's syntax is invalid |
See also:
offsetByCodePoints
public int offsetByCodePoints (int index, int codePointOffset)
Returns the index within this String
that is
offset from the given index
by
codePointOffset
code points. Unpaired surrogates
within the text range given by index
and
codePointOffset
count as one code point each.
Parameters | |
---|---|
index |
int : the index to be offset |
codePointOffset |
int : the offset in code points |
Returns | |
---|---|
int |
the index within this String |
Throws | |
---|---|
IndexOutOfBoundsException |
if index
is negative or larger then the length of this
String , or if codePointOffset is positive
and the substring starting with index has fewer
than codePointOffset code points,
or if codePointOffset is negative and the substring
before index has fewer than the absolute value
of codePointOffset code points. |
regionMatches
public boolean regionMatches (boolean ignoreCase, int toffset, String other, int ooffset, int len)
Tests if two string regions are equal.
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:
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 integer k less thanlen
such that:this.charAt(toffset+k) != other.charAt(ooffset+k)
ignoreCase
istrue
and there is some nonnegative integer k less thanlen
such that:Character.toLowerCase(Character.toUpperCase(this.charAt(toffset+k))) != Character.toLowerCase(Character.toUpperCase(other.charAt(ooffset+k)))
Note that this method does not take locale into account,
and will result in unsatisfactory results for certain locales when
ignoreCase
is true
. The Collator
class
provides locale-sensitive comparison.
Parameters | |
---|---|
ignoreCase |
boolean : if true , ignore case when comparing
characters. |
toffset |
int : the starting offset of the subregion in this
string. |
other |
String : the string argument. |
ooffset |
int : the starting offset of the subregion in the string
argument. |
len |
int : the number of characters to compare. |
Returns | |
---|---|
boolean |
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. |
regionMatches
public boolean regionMatches (int toffset, String other, int ooffset, int len)
Tests if two string regions are equal.
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
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 integer k less than
len
such that:this.charAt(toffset +
k) != other.charAt(ooffset +
k)
Note that this method does not take locale into account. The
Collator
class provides locale-sensitive comparison.
Parameters | |
---|---|
toffset |
int : the starting offset of the subregion in this string. |
other |
String : the string argument. |
ooffset |
int : the starting offset of the subregion in the string
argument. |
len |
int : the number of characters to compare. |
Returns | |
---|---|
boolean |
true if the specified subregion of this string
exactly matches the specified subregion of the string argument;
false otherwise. |
repeat
public String repeat (int count)
Returns a string whose value is the concatenation of this
string repeated count
times.
If this string is empty or count is zero then the empty string is returned.
Parameters | |
---|---|
count |
int : number of times to repeat |
Returns | |
---|---|
String |
A string composed of this string repeated
count times or the empty string if this
string is empty or count is zero |
Throws | |
---|---|
IllegalArgumentException |
if the count is
negative. |
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 |
CharSequence : The sequence of char values to be replaced |
replacement |
CharSequence : The replacement sequence of char values |
Returns | |
---|---|
String |
The resulting string |
replace
public String replace (char oldChar, char newChar)
Returns a string resulting from replacing all occurrences of
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 String
object is returned 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)
Parameters | |
---|---|
oldChar |
char : the old character. |
newChar |
char : the new character. |
Returns | |
---|---|
String |
a string derived from this string by replacing every
occurrence of oldChar with newChar . |
replaceAll
public String replaceAll (String regex, String replacement)
Replaces each substring of this string that matches the given regular expression with the given replacement.
An invocation of this method of the form
str.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; see
Matcher.replaceAll
.
Use Matcher.quoteReplacement(String)
to suppress the special
meaning of these characters, if desired.
Parameters | |
---|---|
regex |
String : the regular expression to which this string is to be matched |
replacement |
String : the string to be substituted for each match |
Returns | |
---|---|
String |
The resulting String |
Throws | |
---|---|
PatternSyntaxException |
if the regular expression's syntax is invalid |
See also:
replaceFirst
public String replaceFirst (String regex, String replacement)
Replaces the first substring of this string that matches the given regular expression with the given replacement.
An invocation of this method of the form
str.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; see
Matcher.replaceFirst(String)
.
Use Matcher.quoteReplacement(String)
to suppress the special
meaning of these characters, if desired.
Parameters | |
---|---|
regex |
String : the regular expression to which this string is to be matched |
replacement |
String : the string to be substituted for the first match |
Returns | |
---|---|
String |
The resulting String |
Throws | |
---|---|
PatternSyntaxException |
if the regular expression's syntax is invalid |
See also:
split
public String[] split (String regex, int limit)
Splits this string around matches of the given regular 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.
The limit
parameter controls the number of times the
pattern is applied and therefore affects the length of the resulting
array.
If the limit is positive then the pattern will be applied at most limit - 1 times, the array's length will be no greater than limit, and the array's last entry will contain all input beyond the last matched delimiter.
If the limit 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.
If the limit is negative then the pattern will be applied as many times as possible and the array can have any length.
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", "", "" }
-2 { "b", "", ":and:f", "", "" }
0 { "b", "", ":and:f" }
An invocation of this method of the form
str.split(
regex,
n)
yields the same result as the expression
Pattern
.compile
(regex).split
(str, n)
Parameters | |
---|---|
regex |
String : the delimiting regular expression |
limit |
int : the result threshold, as described above |
Returns | |
---|---|
String[] |
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 |
See also:
split
public String[] split (String regex)
Splits this string around matches of the given regular expression.
This method works as if by invoking the two-argument 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" }
Parameters | |
---|---|
regex |
String : the delimiting regular expression |
Returns | |
---|---|
String[] |
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 |
See also:
startsWith
public boolean startsWith (String prefix)
Tests if this string starts with the specified prefix.
Parameters | |
---|---|
prefix |
String : the prefix. |
Returns | |
---|---|
boolean |
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(java.lang.Object) method. |
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 |
String : the prefix. |
toffset |
int : where to begin looking in this string. |
Returns | |
---|---|
boolean |
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) |
strip
public String strip ()
Returns a string whose value is this string, with all leading
and trailing white space
removed.
If this String
object represents an empty string,
or if all code points in this string are
white space
, then an empty string
is returned.
Otherwise, returns a substring of this string beginning with the first
code point that is not a white space
up to and including the last code point that is not a
white space
.
This method may be used to strip
white space
from
the beginning and end of a string.
Returns | |
---|---|
String |
a string whose value is this string, with all leading and trailing white space removed |
See also:
stripIndent
public String stripIndent ()
Returns a string whose value is this string, with incidental white space removed from the beginning and end of every line.
Incidental white space is often present in a text block to align the content with the opening delimiter. For example, in the following code, dots represent incidental white space:
This method treats the incidental white space as indentation to be stripped, producing a string that preserves the relative indentation of the content. Using | to visualize the start of each line of the string: String html = """ ..............<html> .............. <body> .............. <p>Hello, world</p> .............. </body> ..............</html> ..............""";
First, the individual lines of this string are extracted. A line is a sequence of zero or more characters followed by either a line terminator or the end of the string. If the string has at least one line terminator, the last line consists of the characters between the last terminator and the end of the string. Otherwise, if the string has no terminators, the last line is the start of the string to the end of the string, in other words, the entire string. A line does not include the line terminator. |<html> | <body> | <p>Hello, world</p> | </body> |</html>
Then, the minimum indentation (min) is determined as follows:
For each non-blank line (as defined by
String#isBlank()
), the leading white space characters are counted.The leading white space characters on the last line are also counted even if blank.
The min value is the smallest of these counts.
For each non-blank line, min leading white space characters are removed, and any trailing space characters are removed. Blank lines are replaced with the empty string.
Finally, the lines are joined into a new string, using the LF character
"\n"
(U+000A) to separate lines.
API Note:
- This method's primary purpose is to shift a block of lines as far as possible to the left, while preserving relative indentation. Lines that were indented the least will thus have no leading white space. The result will have the same number of line terminators as this string. If this string ends with a line terminator then the result will end with a line terminator.
Implementation Requirements:
- This method treats all white space characters as having equal width. As long as the indentation on every line is consistently composed of the same character sequences, then the result will be as described above.
Returns | |
---|---|
String |
string with incidental indentation removed and line terminators normalized |
stripLeading
public String stripLeading ()
Returns a string whose value is this string, with all leading
white space
removed.
If this String
object represents an empty string,
or if all code points in this string are
white space
, then an empty string
is returned.
Otherwise, returns a substring of this string beginning with the first
code point that is not a white space
up to to and including the last code point of this string.
This method may be used to trim
white space
from
the beginning of a string.
Returns | |
---|---|
String |
a string whose value is this string, with all leading white space removed |
See also:
stripTrailing
public String stripTrailing ()
Returns a string whose value is this string, with all trailing
white space
removed.
If this String
object represents an empty string,
or if all characters in this string are
white space
, then an empty string
is returned.
Otherwise, returns a substring of this string beginning with the first
code point of this string up to and including the last code point
that is not a white space
.
This method may be used to trim
white space
from
the end of a string.
Returns | |
---|---|
String |
a string whose value is this string, with all trailing white space removed |
See also:
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
behaves in exactly the same way as the invocation str.subSequence(begin, end)
str.substring(begin, end)
API Note:
- This method is defined so that the
String
class can implement theCharSequence
interface.
Parameters | |
---|---|
beginIndex |
int : the begin index, inclusive. |
endIndex |
int : the end index, exclusive. |
Returns | |
---|---|
CharSequence |
the specified subsequence. |
Throws | |
---|---|
IndexOutOfBoundsException |
if beginIndex or endIndex is negative,
if endIndex is greater than length() ,
or if beginIndex is greater than endIndex |
substring
public String substring (int beginIndex, int endIndex)
Returns a string that is a substring of this string. The
substring begins at the specified 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"
Parameters | |
---|---|
beginIndex |
int : the beginning index, inclusive. |
endIndex |
int : the ending index, exclusive. |
Returns | |
---|---|
String |
the specified substring. |
Throws | |
---|---|
IndexOutOfBoundsException |
if the
beginIndex is negative, or
endIndex is larger than the length of
this String object, or
beginIndex is larger than
endIndex . |
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 |
int : the beginning index, inclusive. |
Returns | |
---|---|
String |
the specified substring. |
Throws | |
---|---|
IndexOutOfBoundsException |
if
beginIndex is negative or larger than the
length of this String object. |
toCharArray
public char[] toCharArray ()
Converts this string to a new character array.
Returns | |
---|---|
char[] |
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. |
toLowerCase
public String toLowerCase ()
Converts all of the characters in this String
to lower
case using the rules of the default locale. This is equivalent to calling
toLowerCase(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, use
toLowerCase(Locale.ROOT)
.
Returns | |
---|---|
String |
the String , converted to lowercase. |
See also:
toLowerCase
public String toLowerCase (Locale locale)
Converts all of the characters in this String
to lower
case using the rules of the given Locale
. Case mapping is based
on the Unicode Standard version specified by the Character
class. 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) | ΙΧΘΥΣ | ιχθυσ | lowercased all chars in String |
Parameters | |
---|---|
locale |
Locale : use the case transformation rules for this locale |
Returns | |
---|---|
String |
the String , converted to lowercase. |
toString
public String toString ()
This object (which is already a string!) is itself returned.
Returns | |
---|---|
String |
the string itself. |
toUpperCase
public String toUpperCase (Locale locale)
Converts all of the characters in this String
to upper
case using the rules of the given Locale
. Case mapping is based
on the Unicode Standard version specified by the Character
class. 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 |
Parameters | |
---|---|
locale |
Locale : use the case transformation rules for this locale |
Returns | |
---|---|
String |
the String , converted to uppercase. |
toUpperCase
public String toUpperCase ()
Converts all of the characters in this String
to upper
case using the rules of the default locale. This method is equivalent to
toUpperCase(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, use
toUpperCase(Locale.ROOT)
.
Returns | |
---|---|
String |
the String , converted to uppercase. |
See also:
transform
public R transform (Function<? super String, ? extends R> f)
This method allows the application of a function to this
string. The function should expect a single String argument
and produce an R
result.
Any exception thrown by f.apply()
will be propagated to the
caller.
Parameters | |
---|---|
f |
Function : a function to apply |
Returns | |
---|---|
R |
the result of applying the function to this string |
See also:
translateEscapes
public String translateEscapes ()
Returns a string whose value is this string, with escape sequences translated as if in a string literal.
Escape sequences are translated as follows;
Escape | Name | Translation |
---|---|---|
\b |
backspace | U+0008 |
\t |
horizontal tab | U+0009 |
\n |
line feed | U+000A |
\f |
form feed | U+000C |
\r |
carriage return | U+000D |
\s |
space | U+0020 |
\" |
double quote | U+0022 |
\' |
single quote | U+0027 |
\\ |
backslash | U+005C |
\0 - \377 |
octal escape | code point equivalents |
\<line-terminator> |
continuation | discard |
Implementation Note:
- This method does not translate Unicode escapes such as "
\u2022
". Unicode escapes are translated by the Java compiler when reading input characters and are not part of the string literal specification.
Returns | |
---|---|
String |
String with escape sequences translated. |
Throws | |
---|---|
IllegalArgumentException |
when an escape sequence is malformed. |
trim
public String trim ()
Returns a string whose value is this string, with all leading
and trailing space removed, where space is defined
as any character whose codepoint is less than or equal to
'U+0020'
(the space character).
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
that are not space (as defined above), then a
reference to this String
object is returned.
Otherwise, if all characters in this string are space (as
defined above), then a String
object representing an
empty string is returned.
Otherwise, let k be the index of the first character in the
string whose code is not a space (as defined above) and let
m be the index of the last character in the string whose code
is not a space (as defined above). A String
object is returned, 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 space (as defined above) from the beginning and end of a string.
Returns | |
---|---|
String |
a string whose value is this string, with all leading and trailing space removed, or this string if it has no leading or trailing space. |
valueOf
public static String valueOf (boolean b)
Returns the string representation of the boolean
argument.
Parameters | |
---|---|
b |
boolean : a boolean . |
Returns | |
---|---|
String |
if the argument is true , a string equal to
"true" is returned; otherwise, a string equal to
"false" is returned. |
valueOf
public static String valueOf (double d)
Returns the string representation of the double
argument.
The representation is exactly the one returned by the
Double.toString
method of one argument.
Parameters | |
---|---|
d |
double : a double . |
Returns | |
---|---|
String |
a string representation of the double argument. |
See also:
valueOf
public static String valueOf (char[] data, int offset, int count)
Returns the string representation of a specific subarray of the
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 returned string.
Parameters | |
---|---|
data |
char : the character array. |
offset |
int : initial offset of the subarray. |
count |
int : length of the subarray. |
Returns | |
---|---|
String |
a String that contains the characters of the
specified subarray of the character array. |
Throws | |
---|---|
IndexOutOfBoundsException |
if offset is
negative, or count is negative, or
offset+count is larger than
data.length . |
valueOf
public static String valueOf (float f)
Returns the string representation of the float
argument.
The representation is exactly the one returned by the
Float.toString
method of one argument.
Parameters | |
---|---|
f |
float : a float . |
Returns | |
---|---|
String |
a string representation of the float argument. |
See also:
valueOf
public static String valueOf (int i)
Returns the string representation of the int
argument.
The representation is exactly the one returned by the
Integer.toString
method of one argument.
Parameters | |
---|---|
i |
int : an int . |
Returns | |
---|---|
String |
a string representation of the int argument. |
See also:
valueOf
public static String valueOf (char c)
Returns the string representation of the char
argument.
Parameters | |
---|---|
c |
char : a char . |
Returns | |
---|---|
String |
a string of length 1 containing
as its single character the argument c . |
valueOf
public static String valueOf (long l)
Returns the string representation of the long
argument.
The representation is exactly the one returned by the
Long.toString
method of one argument.
Parameters | |
---|---|
l |
long : a long . |
Returns | |
---|---|
String |
a string representation of the long argument. |
See also:
valueOf
public static String valueOf (Object obj)
Returns the string representation of the Object
argument.
Parameters | |
---|---|
obj |
Object : an Object . |
Returns | |
---|---|
String |
if the argument is null , then a string equal to
"null" ; otherwise, the value of
obj.toString() is returned. |
See also:
valueOf
public static String valueOf (char[] data)
Returns the string representation of the char
array
argument. The contents of the character array are copied; subsequent
modification of the character array does not affect the returned
string.
Parameters | |
---|---|
data |
char : the character array. |
Returns | |
---|---|
String |
a String that contains the characters of the
character array. |