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String name = new String("Alex");
Based on 8 examples
StringBuffer sb = …;
String s = sb.toString();
Based on 6 examples
public final class String extends Object implements Serializable, Comparable, CharSequence
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 {@link java.lang.Character Character} class.
The Java language provides special support for the string
concatenation operator ( + ), and for conversion of
other objects to strings. String concatenation is implemented
through the StringBuilder
(or 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 {@link 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).
Field Summary | |
---|---|
static Comparator |
CASE_INSENSITIVE_ORDER
A Comparator that orders String objects as by
compareToIgnoreCase . |
Constructor Summary | |
---|---|
String() Initializes a newly created object so that it represents an empty character sequence. |
|
String(byte[] bytes) Constructs a new by decoding the specified array of bytes using the platform's default charset. |
|
Constructs a new by decoding the specified array of bytes using the specified java.nio.charset.Charset. |
|
String(byte[] ascii, int hibyte) Allocates a new containing characters constructed from an array of 8-bit integer values. |
|
String(byte[] bytes, int offset, int length) Constructs a new by decoding the specified subarray of bytes using the platform's default charset. |
|
Constructs a new by decoding the specified subarray of bytes using the specified java.nio.charset.Charset. |
|
String(byte[] ascii, int hibyte, int offset, int count) Allocates a new constructed from a subarray of an array of 8-bit integer values. |
|
Constructs a new by decoding the specified subarray of bytes using the specified charset. |
|
Constructs a new by decoding the specified array of bytes using the specified java.nio.charset.Charset. |
|
String(char[] value) Allocates a new so that it represents the sequence of characters currently contained in the character array argument. |
|
String(char[] value, int offset, int count) Allocates a new that contains characters from a subarray of the character array argument. |
|
String(int[] codePoints, int offset, int count) Allocates a new that contains characters from a subarray of the Unicode code point array argument. |
|
Initializes a newly created object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string. |
|
String(StringBuffer buffer) Allocates a new string that contains the sequence of characters currently contained in the string buffer argument. |
|
String(StringBuilder builder) Allocates a new string that contains the sequence of characters currently contained in the string builder argument. |
Method Summary | |
---|---|
char |
charAt(int index) Returns the char value at the
specified index.
|
int |
codePointAt(int index) Returns the character (Unicode code point) at the specified index. |
int |
codePointBefore(int index) Returns the character (Unicode code point) before the specified index. |
int |
codePointCount(int beginIndex, int endIndex) Returns the number of Unicode code points in the specified text range of this String .
|
int |
Compares two strings lexicographically. |
int |
Compares two strings lexicographically, ignoring case differences. |
String |
Concatenates the specified string to the end of this string. |
boolean |
Returns true if and only if this string contains the specified sequence of char values. |
boolean |
Compares this string to the specified . |
boolean |
Compares this string to the specified . |
static String |
copyValueOf(char[] data) Returns a String that represents the character sequence in the array specified. |
static String |
copyValueOf(char[] data, int offset, int count) Returns a String that represents the character sequence in the array specified. |
boolean |
Tests if this string ends with the specified suffix. |
boolean |
Compares this string to the specified object. |
boolean |
equalsIgnoreCase(String anotherString) Compares this to another , ignoring case considerations. |
static String |
Returns a formatted string using the specified locale, format string, and arguments. |
static String |
Returns a formatted string using the specified format string and arguments. |
byte[] |
getBytes() Encodes this into a sequence of bytes using the platform's default charset, storing the result into a new byte array. |
byte[] |
Encodes this into a sequence of bytes using the given java.nio.charset.Charset, storing the result into a new byte array. |
void |
getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin) Copies characters from this string into the destination byte array. |
byte[] |
Encodes this into a sequence of bytes using the named charset, storing the result into a new byte array. |
void |
getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) Copies characters from this string into the destination character array. |
int |
hashCode() Returns a hash code for this string. |
int |
indexOf(int ch) Returns the index within this string of the first occurrence of the specified character. |
int |
indexOf(int ch, int fromIndex) Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index. |
int |
Returns the index within this string of the first occurrence of the specified substring. |
int |
Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. |
native String |
intern() Returns a canonical representation for the string object. |
boolean |
isEmpty() Returns true if, and only if, java.lang.String.length is 0. |
int |
lastIndexOf(int ch) Returns the index within this string of the last occurrence of the specified character. |
int |
lastIndexOf(int ch, int fromIndex) Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index. |
int |
lastIndexOf(String str) Returns the index within this string of the rightmost occurrence of the specified substring. |
int |
lastIndexOf(String str, int fromIndex) Returns the index within this string of the last occurrence of the specified substring, searching backward starting at the specified index. |
int |
length() Returns the length of this string. |
boolean |
Tells whether or not this string matches the given regular expression. |
int |
offsetByCodePoints(int index, int codePointOffset) Returns the index within this String that is
offset from the given index by
codePointOffset code points.
|
boolean |
regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len) Tests if two string regions are equal. |
boolean |
regionMatches(int toffset, String other, int ooffset, int len) Tests if two string regions are equal. |
String |
replace(char oldChar, char newChar) Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar .
|
String |
replace(CharSequence target, CharSequence replacement) Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. |
String |
replaceAll(String regex, String replacement) Replaces each substring of this string that matches the given regular expression with the given replacement. |
String |
replaceFirst(String regex, String replacement) Replaces the first substring of this string that matches the given regular expression with the given replacement. |
String[] |
Splits this string around matches of the given regular expression. |
String[] |
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. |
CharSequence |
subSequence(int beginIndex, int endIndex) Returns a new character sequence that is a subsequence of this sequence. |
String |
substring(int beginIndex) Returns a new string that is a substring of this string. |
String |
substring(int beginIndex, int endIndex) Returns a new string that is a substring of this string. |
char[] |
Converts this string to a new character array. |
String |
Converts all of the characters in this String to lower
case using the rules of the default locale.
|
String |
toLowerCase(Locale locale) Converts all of the characters in this String to lower
case using the rules of the given Locale .
|
String |
toString() This object (which is already a string!) is itself returned. |
String |
Converts all of the characters in this String to upper
case using the rules of the default locale.
|
String |
toUpperCase(Locale locale) Converts all of the characters in this String to upper
case using the rules of the given Locale .
|
String |
trim() Returns a copy of the string, with leading and trailing whitespace omitted. |
String |
truncate(int maxLength) Returns a new string with a length no longer than maxLength characters.
|
static String |
valueOf(boolean b) Returns the string representation of the boolean argument.
|
static String |
valueOf(char c) Returns the string representation of the char
argument.
|
static String |
valueOf(char[] data) Returns the string representation of the char array
argument.
|
static String |
valueOf(char[] data, int offset, int count) Returns the string representation of a specific subarray of the char array argument.
|
static String |
valueOf(double d) Returns the string representation of the double argument.
|
static String |
valueOf(float f) Returns the string representation of the float argument.
|
static String |
valueOf(int i) Returns the string representation of the int argument.
|
static String |
valueOf(long l) Returns the string representation of the long argument.
|
static String |
Returns the string representation of the Object argument.
|
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
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()
public String(byte[] bytes)
The behavior of this constructor when the given bytes are not valid in the default charset is unspecified. The {@link 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(byte[] bytes, Charset charset)
This method always replaces malformed-input and unmappable-character sequences with this charset's default replacement string. The {@link java.nio.charset.CharsetDecoder} class should be used when more control over the decoding process is required.
bytes
- The bytes to be decoded into characterscharset
- The {@linkplain java.nio.charset.Charset charset} to be used to
decode the {@code bytes}public String(byte[] ascii, int hibyte)
c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
ascii
- The bytes to be converted to charactershibyte
- The top 8 bits of each 16-bit Unicode code unitpublic 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 {@link 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 decodepublic String(byte[] bytes, int offset, int length, Charset charset)
This method always replaces malformed-input and unmappable-character sequences with this charset's default replacement string. The {@link 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 decodecharset
- The {@linkplain java.nio.charset.Charset charset} to be used to
decode the {@code bytes}public String(byte[] ascii, int hibyte, int offset, int count)
The {@code offset} argument is the index of the first byte of the subarray, and the {@code count} argument specifies the length of the subarray.
Each {@code byte} in the subarray is converted to a {@code char} as specified in the method above.
ascii
- The bytes to be converted to charactershibyte
- The top 8 bits of each 16-bit Unicode code unitoffset
- The initial offsetcount
- The lengthpublic String(byte[] bytes, int offset, int length, String charsetName) throws UnsupportedEncodingException
The behavior of this constructor when the given bytes are not valid in the given charset is unspecified. The {@link 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 {@linkplain java.nio.charset.Charset
charset}UnsupportedEncodingException
- If the named charset is not supportedpublic String(byte[] bytes, String charsetName) throws UnsupportedEncodingException
The behavior of this constructor when the given bytes are not valid in the given charset is unspecified. The {@link 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 {@linkplain java.nio.charset.Charset
charset}UnsupportedEncodingException
- If the named charset is not supportedpublic String(char[] value)
value
- The initial value of the stringpublic String(char[] value, int offset, int count)
value
- Array that is the source of charactersoffset
- The initial offsetcount
- The lengthpublic String(int[] codePoints, int offset, int count)
codePoints
- Array that is the source of Unicode code pointsoffset
- The initial offsetcount
- The lengthpublic String(String original)
original
- A {@code String}public String(StringBuffer buffer)
buffer
- A {@code StringBuffer}public String(StringBuilder builder)
This constructor is provided to ease migration to {@code StringBuilder}. Obtaining a string from a string builder via the {@code toString} method is likely to run faster and is generally preferred.
builder
- A {@code StringBuilder}Method Detail |
---|
public char charAt(int index)
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.
index
- the index of the char
value.char
value at the specified index of this string.
The first char
value is at index 0
.public int codePointAt(int index)
char
values
(Unicode code units) and ranges from 0
to
{@link #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.
index
- the index to the char
valuesindex
public int codePointBefore(int index)
char
values
(Unicode code units) and ranges from 1
to {@link
CharSequence#length() 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.
index
- the index following the code point that should be returnedpublic int codePointCount(int beginIndex, int endIndex)
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.
beginIndex
- the index to the first char
of
the text range.endIndex
- the index after the last char
of
the text range.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 {@link #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 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 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 boolean contains(CharSequence s)
s
- the sequence to search fors
, false otherwisepublic boolean contentEquals(CharSequence cs)
cs
- The sequence to compare this {@code String} againstpublic boolean contentEquals(StringBuffer sb)
sb
- The {@code StringBuffer} to compare this {@code String} againstpublic static String copyValueOf(char[] data)
data
- the character array.String
that contains the characters of the
character array.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 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 {@link #equals(Object)} method.public boolean equals(Object anObject)
equals
in class Object
anObject
- The object to compare this {@code String} againstpublic boolean equalsIgnoreCase(String anotherString)
Two characters {@code c1} and {@code c2} are considered the same ignoring case if at least one of the following is true:
anotherString
- The {@code String} to compare this {@code String} againstpublic static String format(Locale l, String format, Object[] args)
l
- The {@linkplain java.util.Locale locale} to apply during
formatting. If l is null then no localization
is applied.format
- A format stringargs
- 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.public static String format(String format, Object[] args)
The locale always used is the one returned by {@link java.util.Locale#getDefault() Locale.getDefault()}.
format
- A format stringargs
- 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.public byte[] getBytes()
The behavior of this method when this string cannot be encoded in the default charset is unspecified. The {@link java.nio.charset.CharsetEncoder} class should be used when more control over the encoding process is required.
public byte[] getBytes(Charset charset)
This method always replaces malformed-input and unmappable-character sequences with this charset's default replacement byte array. The {@link java.nio.charset.CharsetEncoder} class should be used when more control over the encoding process is required.
charset
- The {@linkplain java.nio.charset.Charset} to be used to encode
the {@code String}public void getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)
The first character to be copied is at index {@code srcBegin}; the last character to be copied is at index {@code srcEnd-1}. The total number of characters to be copied is {@code srcEnd-srcBegin}. The characters, converted to bytes, are copied into the subarray of {@code dst} starting at index {@code dstBegin} and ending at index:
dstbegin + (srcEnd-srcBegin) - 1
srcBegin
- Index of the first character in the string to copysrcEnd
- Index after the last character in the string to copydst
- The destination arraydstBegin
- The start offset in the destination arraypublic byte[] getBytes(String charsetName) throws UnsupportedEncodingException
The behavior of this method when this string cannot be encoded in the given charset is unspecified. The {@link java.nio.charset.CharsetEncoder} class should be used when more control over the encoding process is required.
charsetName
- The name of a supported {@linkplain java.nio.charset.Charset
charset}UnsupportedEncodingException
- If the named charset is not supportedpublic 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.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.)
hashCode
in class Object
public int indexOf(int ch)
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 ofthis.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, thenthis.codePointAt(k) == ch
-1
is returned.
ch
- a character (Unicode code point).-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. 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).
ch
- a character (Unicode code point).fromIndex
- the index to start the search from.fromIndex
, or -1
if the character does not occur.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, this.length()) && this.startsWith(str, k)
str
- the substring for which to search.fromIndex
- the index from which to start the search.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 {@link #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
public boolean isEmpty()
public int lastIndexOf(int ch)
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 ofthis.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, thenthis.codePointAt(k) == ch
-1
is returned. The
String
is searched backwards starting at the last
character.
ch
- a character (Unicode code point).-1
if the character does not occur.public int lastIndexOf(int ch, int fromIndex)
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).
ch
- a character (Unicode code point).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 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, this.length()) && this.startsWith(str, k)
str
- the substring to search for.fromIndex
- the index to start the search from.public int length()
public boolean matches(String regex)
An invocation of this method of the form str.matches(regex) yields exactly the same result as the expression
{@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#matches(String,CharSequence) matches}(regex, str)
regex
- the regular expression to which this string is to be matchedpublic int offsetByCodePoints(int index, int codePointOffset)
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.
index
- the index to be offsetcodePointOffset
- the offset in code pointsString
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 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 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 String replace(CharSequence target, CharSequence replacement)
target
- The sequence of char values to be replacedreplacement
- The replacement sequence of char valuespublic 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
{@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile compile}(regex).{@link java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(str).{@link java.util.regex.Matcher#replaceAll 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 {@link java.util.regex.Matcher#replaceAll Matcher.replaceAll}. Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special meaning of these characters, if desired.
regex
- the regular expression to which this string is to be matchedreplacement
- the string to be substituted for each matchpublic 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
{@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile compile}(regex).{@link java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(str).{@link java.util.regex.Matcher#replaceFirst 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 {@link java.util.regex.Matcher#replaceFirst}. Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special meaning of these characters, if desired.
regex
- the regular expression to which this string is to be matchedreplacement
- the string to be substituted for the first matchpublic String[] split(String regex)
This method works as if by invoking the two-argument {@link #split(String, 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 expressionpublic 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
{@link java.util.regex.Pattern}.{@link java.util.regex.Pattern#compile compile}(regex).{@link java.util.regex.Pattern#split(java.lang.CharSequence,int) split}(str, n)
regex
- the delimiting regular expressionlimit
- the result threshold, as described abovepublic 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
{@link #equals(Object)} method.public boolean startsWith(String prefix, int toffset)
prefix
- the prefix.toffset
- where to begin looking in this 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 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 {@link CharSequence} interface.str.substring(begin, end)
beginIndex
- the begin index, inclusive.endIndex
- the end index, exclusive.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.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.public char[] toCharArray()
public String toLowerCase()
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?tle"
, where '?' is the LATIN SMALL
LETTER DOTLESS I character.
To obtain correct results for locale insensitive strings, use
toLowerCase(Locale.ENGLISH)
.
String
, converted to lowercase.public String toLowerCase(Locale locale)
String
to lower
case using the rules of the given Locale
. Case mapping is based
on the Unicode Standard version specified by the {@link java.lang.Character 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) | lowercased all chars in String |
locale
- use the case transformation rules for this localeString
, converted to lowercase.public String toString()
toString
in class Object
public String toUpperCase()
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?TLE"
, where '?' is the LATIN CAPITAL
LETTER I WITH DOT ABOVE character.
To obtain correct results for locale insensitive strings, use
toUpperCase(Locale.ENGLISH)
.
String
, converted to uppercase.public String toUpperCase(Locale locale)
String
to upper
case using the rules of the given Locale
. Case mapping is based
on the Unicode Standard version specified by the {@link java.lang.Character 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 |
locale
- use the case transformation rules for this localeString
, 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 (as defined above) from the beginning and end of a string.
public String truncate(int maxLength)
maxLength
characters.org.apache.commons.lang.StringUtils
which can apparently do this and a lot more.
maxLength
maxLength
characterspublic 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(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
.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 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(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(Object obj)
Object
argument.
obj
- an Object
.null
, then a string equal to
"null"
; otherwise, the value of
obj.toString()
is returned.
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