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java.lang.Object | +----java.lang.String
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.
The Java language provides special support for the string
concatentation operator ( + ), and for conversion of
other objects to strings. String concatenation is implemented
through the StringBuffer
class and its
append
method.
String conversions are implemented through the method
toString
, defined by Object
and
inherited by all classes in Java. For additional information on
string concatenation and conversion, see Gosling, Joy, and Steele,
The Java Language Specification.
Constructor Summary | |
String()
String containing no characters.
|
|
String(String value)
|
|
String(char[] value)
String so that it represents the
sequence of characters currently contained in the character array
argument.
|
|
String(char[] value,
int offset,
int count)
String that contains characters from
a subarray of the character array argument.
|
|
String(byte[] ascii,
int hibyte,
int offset,
int count)
String constructed from a subarray
of an array of 8-bit integer values.
Deprecated |
|
String(byte[] ascii,
int hibyte)
String containing characters
constructed from an array of 8-bit integer values.
Deprecated |
|
String(byte[] bytes,
int offset,
int length,
String enc)
String by converting the specified
subarray of bytes using the specified character encoding.
|
|
String(byte[] bytes,
String enc)
String by converting the specified array
of bytes using the specified character encoding.
|
|
String(byte[] bytes,
int offset,
int length)
String by converting the specified
subarray of bytes using the platform's default character encoding.
|
|
String(byte[] bytes)
String by converting the specified array
of bytes using the platform's default character encoding.
|
|
String(StringBuffer buffer)
|
Method Summary | |
char | charAt(int index)
|
int | compareTo(String anotherString)
|
int | compareTo(Object o)
|
String | concat(String str)
|
static String | copyValueOf(char[] data,
int offset,
int count)
|
static String | copyValueOf(char[] data)
|
boolean | endsWith(String suffix)
|
boolean | equals(Object anObject)
|
boolean | equalsIgnoreCase(String anotherString)
|
void | getBytes(int srcBegin,
int srcEnd,
byte[] dst,
int dstBegin)
|
byte[] | getBytes(String enc)
String into bytes according to the specified
character encoding, storing the result into a new byte array.
|
byte[] | getBytes()
String into bytes according to the platform's
default character encoding, storing the result into a new byte array.
|
void | getChars(int srcBegin,
int srcEnd,
char[] dst,
int dstBegin)
|
int | hashCode()
|
int | indexOf(int ch)
|
int | indexOf(int ch,
int fromIndex)
|
int | indexOf(String str)
|
int | indexOf(String str,
int fromIndex)
|
String | intern()
|
int | lastIndexOf(int ch)
|
int | lastIndexOf(int ch,
int fromIndex)
|
int | lastIndexOf(String str)
|
int | lastIndexOf(String str,
int fromIndex)
|
int | length()
|
boolean | regionMatches(int toffset,
String other,
int ooffset,
int len)
|
boolean | regionMatches(boolean ignoreCase,
int toffset,
String other,
int ooffset,
int len)
|
String | replace(char oldChar,
char newChar)
oldChar in this string with newChar .
|
boolean | startsWith(String prefix,
int toffset)
|
boolean | startsWith(String prefix)
|
String | substring(int beginIndex)
|
String | substring(int beginIndex,
int endIndex)
|
char[] | toCharArray()
|
String | toLowerCase(Locale locale)
String to lower
case using the rules of the given locale.
|
String | toLowerCase()
String to lowercase.
|
String | toString()
|
String | toUpperCase(Locale locale)
String to upper
case using the rules of the given locale.
|
String | toUpperCase()
|
String | trim()
|
static String | valueOf(Object obj)
Object argument.
|
static String | valueOf(char[] data)
char array
argument.
|
static String | valueOf(char[] data,
int offset,
int count)
char array argument.
|
static String | valueOf(boolean b)
boolean argument.
|
static String | valueOf(char c)
char * argument.
|
static String | valueOf(int i)
int argument.
|
static String | valueOf(long l)
long argument.
|
static String | valueOf(float f)
float argument.
|
static String | valueOf(double d)
double argument.
|
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public String()
String
containing no characters.public String(String value)
value
- a String
.
public String(char[] value)
String
so that it represents the
sequence of characters currently contained in the character array
argument.
value
- the initial value of the string.
public String(char[] value, int offset, int count)
String
that contains characters from
a subarray of the character array argument. The offset
argument is the index of the first character of the subarray and
the count
argument specifies the length of the
subarray.
value
- array that is the source of characters.
offset
- the initial offset.
count
- the length.
offset
and count
arguments index characters outside
the bounds of the value
array.public String(byte[] ascii, int hibyte, int offset, int count)
String
constructors that take a character-encoding name or
that use the platform's default encoding.
String
constructed from a subarray
of an array of 8-bit integer values.
The offset
argument is the index of the first byte
of the subarray, and the count
argument specifies the
length of the subarray.
Each byte
in the subarray is converted to a
char
as specified in the method above.
ascii
- the bytes to be converted to characters.
hibyte
- the top 8 bits of each 16-bit Unicode character.
offset
- the initial offset.
count
- the length.
offset
or count
argument is invalid.public String(byte[] ascii, int hibyte)
String
constructors that take a character-encoding name or
that use the platform's default encoding.
String
containing characters
constructed from an array of 8-bit integer values. Each character
cin the resulting string is constructed from the
corresponding component b in the byte array such that:
c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
ascii
- the bytes to be converted to characters.
hibyte
- the top 8 bits of each 16-bit Unicode character.
public String(byte[] bytes, int offset, int length, String enc) throws UnsupportedEncodingException
String
by converting the specified
subarray of bytes using the specified character encoding. The length of
the new String
is a function of the encoding, and hence may
not be equal to the length of the subarray.
bytes
- The bytes to be converted into characters
offset
- Index of the first byte to convert
length
- Number of bytes to convert
enc
- The name of a character encoding
public String(byte[] bytes, String enc) throws UnsupportedEncodingException
String
by converting the specified array
of bytes using the specified character encoding. The length of the new
String
is a function of the encoding, and hence may not be
equal to the length of the byte array.
bytes
- The bytes to be converted into characters
enc
- A character-encoding name
public String(byte[] bytes, int offset, int length)
String
by converting the specified
subarray of bytes using the platform's default character encoding. The
length of the new String
is a function of the encoding, and
hence may not be equal to the length of the subarray.
bytes
- The bytes to be converted into characters
offset
- Index of the first byte to convert
length
- Number of bytes to convert
public String(byte[] bytes)
String
by converting the specified array
of bytes using the platform's default character encoding. The length of
the new String
is a function of the encoding, and hence may
not be equal to the length of the byte array.
bytes
- The bytes to be converted into characters
public String(StringBuffer buffer)
buffer
- a StringBuffer
.
Method Detail |
public int length()
public char charAt(int index)
0
to length() - 1
.
index
- the index of the character.
0
.public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
The first character to be copied is at index srcBegin
;
the last character to be copied is at index srcEnd-1
(thus the total number of characters to be copied is
srcEnd-srcBegin
). The characters are copied into the
subarray of dst
starting at index dstBegin
and ending at index:
dstbegin + (srcEnd-srcBegin) - 1
srcBegin
- index of the first character in the string
to copy.
srcEnd
- index after the last character in the string
to copy.
dst
- the destination array.
dstBegin
- the start offset in the destination array.
public void getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)
getBytes(String enc)
method, which takes a
character-encoding name, or the getBytes()
method, which
uses the platform's default encoding.
The first character to be copied is at index srcBegin
;
the last character to be copied is at index srcEnd-1
.
The total number of characters to be copied is
srcEnd-srcBegin
. The characters, converted to bytes,
are copied into the subarray of dst
starting at index
dstBegin
and ending at index:
dstbegin + (srcEnd-srcBegin) - 1
srcBegin
- index of the first character in the string
to copy.
srcEnd
- index after the last character in the string
to copy.
dst
- the destination array.
dstBegin
- the start offset in the destination array.
public byte[] getBytes(String enc) throws UnsupportedEncodingException
String
into bytes according to the specified
character encoding, storing the result into a new byte array.
enc
- A character-encoding name
public byte[] getBytes()
String
into bytes according to the platform's
default character encoding, storing the result into a new byte array.public boolean equals(Object anObject)
true
if and only if the argument is not
null
and is a String
object that represents
the same sequence of characters as this object.
anObject
- the object to compare this String
against.
true
if the String
are equal;
false
otherwise.public boolean equalsIgnoreCase(String anotherString)
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, where case is ignored.
Two characters are considered the same, ignoring case, if at least one of the following is true:
==
operator).
Character.toUppercase
to each
character produces the same result.
Character.toLowercase
to each
character produces the same result.
Two sequences of characters are the same, ignoring case, if the sequences have the same length and corresponding characters are the same, ignoring case.
anotherString
- the String
to compare this
String
against.
true
if the String
s are equal,
ignoring case; false
otherwise.public int compareTo(String anotherString)
anotherString
- the String
to be compared.
0
if the argument string is equal to
this string; a value less than 0
if this string
is lexicographically less than the string argument; and a
value greater than 0
if this string is
lexicographically greater than the string argument.public int compareTo(Object o)
compareTo(String)
. Otherwise,
it throws a ClassCastException
(as Strings are comparable
only to other Strings).
o
- the Object
to be compared.
0
if the argument is a string
lexicographically equal to this string; a value less than
0
if the argument is a string lexicographically
greater than this string; and a value greater than
0
if the argument is a string lexicographically
less than this string.ClassCastException
- if the argument is not a
String
.public boolean regionMatches(int toffset, String other, int ooffset, int len)
If toffset
or ooffset
is negative, or
if toffset
+length
is greater than the
length of this string, or if
ooffset
+length
is greater than the
length of the string argument, then this method returns
false
.
toffset
- the starting offset of the subregion in this string.
other
- the string argument.
ooffset
- the starting offset of the subregion in the string
argument.
len
- the number of characters to compare.
true
if the specified subregion of this string
exactly matches the specified subregion of the string argument;
false
otherwise.public boolean regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)
If toffset
or ooffset
is negative, or
if toffset
+length
is greater than the
length of this string, or if
ooffset
+length
is greater than the
length of the string argument, then this method returns
false
.
ignoreCase
- if true
, ignore case when comparing
characters.
toffset
- the starting offset of the subregion in this
string.
other
- the string argument.
ooffset
- the starting offset of the subregion in the string
argument.
len
- the number of characters to compare.
true
if the specified subregion of this string
matches the specified subregion of the string argument;
false
otherwise. Whether the matching is exact
or case insensitive depends on the ignoreCase
argument.public boolean startsWith(String prefix, int toffset)
prefix
- the prefix.
toffset
- where to begin looking in the string.
true
if the character sequence represented by the
argument is a prefix of the substring of this object starting
at index toffset
; false
otherwise.public boolean startsWith(String prefix)
prefix
- the prefix.
true
if the character sequence represented by the
argument is a prefix of the character sequence represented by
this string; false
otherwise.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.public int hashCode()
public int indexOf(int ch)
ch
- a character.
-1
if the character does not occur.public int indexOf(int ch, int fromIndex)
ch
- a character.
fromIndex
- the index to start the search from.
fromIndex
, or -1
if the character does not occur.public int lastIndexOf(int ch)
ch
- a character.
-1
if the character does not occur.public int lastIndexOf(int ch, int fromIndex)
ch
- a character.
fromIndex
- the index to start the search from.
fromIndex
, or -1
if the character does not occur before that point.public int indexOf(String str)
str
- any string.
-1
is returned.public int indexOf(String str, int fromIndex)
str
- the substring to search for.
fromIndex
- the index to start the search from.
fromIndex
, then the index of the first character
of the first such substring is returned. If it does not occur
as a substring starting at fromIndex
or beyond,
-1
is returned.public int lastIndexOf(String str)
this.length()
.
str
- the substring to search for.
-1
is returned.public int lastIndexOf(String str, int fromIndex)
fromIndex
.
str
- the substring to search for.
fromIndex
- the index to start the search from.
fromIndex
, then the index of the first character of
the last such substring is returned. If it does not occur as a
substring starting at fromIndex
or earlier,
-1
is returned.public String substring(int beginIndex)
beginIndex
- the beginning index, inclusive.
beginIndex
is out of range.public String substring(int beginIndex, int endIndex)
beginIndex
and
extends to the character at index endIndex - 1
.
beginIndex
- the beginning index, inclusive.
endIndex
- the ending index, exclusive.
beginIndex
or the endIndex
is
out of range.public String concat(String str)
If the length of the argument string is 0
, then this
object is returned.
str
- the String
that is concatenated to the end
of this String
.
public String replace(char oldChar, char newChar)
oldChar
in this string with newChar
.
If the character oldChar
does not occur in the
character sequence represented by this object, then this string is
returned.
oldChar
- the old character.
newChar
- the new character.
oldChar
with newChar
.public String toLowerCase(Locale locale)
String
to lower
case using the rules of the given locale.
locale
- use the case transformation rules for this locale
public String toLowerCase()
String
to lowercase.
If no character in the string has a different lowercase version,
based on calling the toLowerCase
method defined by
Character
, then the original string is returned.
Otherwise, a new string is allocated, whose length is identical to this string, and such that each character that has a different lowercase version is mapped to this lowercase equivalent.
public String toUpperCase(Locale locale)
String
to upper
case using the rules of the given locale.
locale
- use the case transformation rules for this locale
public String toUpperCase()
If no character in this string has a different uppercase version,
based on calling the toUpperCase
method defined by
Character
, then the original string is returned.
Otherwise, a new string is allocated, whose length is identical to this string, and such that each character that has a different uppercase version is mapped to this uppercase equivalent.
public String trim()
All characters that have codes less than or equal to
'\u0020'
(the space character) are considered to be
white space.
public String toString()
public char[] toCharArray()
public static String valueOf(Object obj)
Object
argument.
obj
- an Object
.
null
, then a string equal to
"null"
; otherwise, the value of
obj.toString()
is returned.public static String valueOf(char[] data)
char
array
argument.
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.
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 copyValueOf(char[] data, int offset, int count)
data
- the character array.
offset
- initial offset of the subarray.
count
- length of the subarray.
String
that contains the characters of the
specified subarray of the character array.public static String copyValueOf(char[] data)
data
- the character array.
String
that contains the characters of the
character array.public static String valueOf(boolean b)
boolean
argument.
b
- a boolean
.
true
, a string equal to
"true"
is returned; otherwise, a string equal to
"false"
is returned.public static String valueOf(char c)
char
* argument.
c
- a char
.
1
containing
as its single character the argument c
.public static String valueOf(int i)
int
argument.
The representation is exactly the one returned by the
Integer.toString
method of one argument.
i
- an int
.
int
argument.public static String valueOf(long l)
long
argument.
The representation is exactly the one returned by the
Long.toString
method of one argument.
l
- a long
.
long
argument.public static String valueOf(float f)
float
argument.
The representation is exactly the one returned by the
Float.toString
method of one argument.
f
- a float
.
float
argument.public static String valueOf(double d)
double
argument.
The representation is exactly the one returned by the
Double.toString
method of one argument.
d
- a double
.
double
argument.public String intern()
If s
and t
are strings such that
s.equals(t)
, it is guaranteed that
s.intern() == t.intern().
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