java.lang.String

public final class java.lang

String

Java SE 6

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 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 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).

version 1.204, 06/09/06

since JDK1.0

See also toString(), java.lang.StringBuffer, java.lang.StringBuilder, java.nio.charset.Charset

Fields

final public static Comparator

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 java.text package provides Collators to allow locale-sensitive ordering.

since 1.2

See also compare(String, String)

Constructors

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.

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.

original A 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.

value

The initial value of the 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.

value	Array that is the source of characters
offset	The initial offset
count	The length
Throws	IndexOutOfBoundsException: If the `offset` and `count` arguments index characters outside the bounds of the `value` array

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 chars; subsequent modification of the int array does not affect the newly created string.

codePoints	Array that is the source of Unicode code points
offset	The initial offset
count	The length
Throws	IllegalArgumentException: If any invalid Unicode code point is found in `codePoints`
Throws	IndexOutOfBoundsException: If the `offset` and `count` arguments index characters outside the bounds of the `codePoints` array
since	1.5

public

String(byte[] ascii, int hibyte, int offset, int count)

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 method above.

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 java.nio.charset.Charset, charset name, or that use the platform's default charset.

ascii The bytes to be converted to characters

hibyte The top 8 bits of each 16-bit Unicode code unit

offset The initial offset

count The length

Throws IndexOutOfBoundsException: If the offset or count argument is invalid

See also String(byte[], int), String(byte[], int, int, java.lang.String), String(byte[], int, int, java.nio.charset.Charset), String(byte[], int, int), String(byte[], java.lang.String), String(byte[], java.nio.charset.Charset), String(byte[])

public

String(byte[] ascii, int hibyte)

Allocates a new 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))

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 `java.nio.charset.Charset`, charset name, or that use the platform's default charset.
ascii	The bytes to be converted to characters
hibyte	The top 8 bits of each 16-bit Unicode code unit
See also	String(byte[], int, int, java.lang.String), String(byte[], int, int, java.nio.charset.Charset), String(byte[], int, int), String(byte[], java.lang.String), String(byte[], java.nio.charset.Charset), String(byte[])

public

String(byte[] bytes, int offset, int length, String charsetName) throws UnsupportedEncodingException
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.

The behavior of this constructor when the given bytes are not valid in the given charset is unspecified. The java.nio.charset.CharsetDecoder class should be used when more control over the decoding process is required.

bytes The bytes to be decoded into characters

offset The index of the first byte to decode

length The number of bytes to decode

charsetName The name of a supported charset

Throws UnsupportedEncodingException: If the named charset is not supported

Throws IndexOutOfBoundsException: If the offset and length arguments index characters outside the bounds of the bytes array

since JDK1.1

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 java.nio.charset.CharsetDecoder class should be used when more control over the decoding process is required.

bytes The bytes to be decoded into characters

offset The index of the first byte to decode

length The number of bytes to decode

charset The charset to be used to decode the bytes

Throws IndexOutOfBoundsException: If the offset and length arguments index characters outside the bounds of the bytes array

since 1.6

public

String(byte[] bytes, String charsetName) throws UnsupportedEncodingException
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.

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.

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 java.nio.charset.CharsetDecoder class should be used when more control over the decoding process is required.

bytes The bytes to be decoded into characters

offset The index of the first byte to decode

length The number of bytes to decode

Throws IndexOutOfBoundsException: If the offset and the length arguments index characters outside the bounds of the bytes array

since JDK1.1

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.

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.

buffer A StringBuffer

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.

builder A StringBuilder

since 1.5

Methods

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.

index the index of the char value.

return 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.

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.

index the index to the char values

return 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.

since 1.5

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.

index the index following the code point that should be returned

return 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.

since 1.5

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 chars) 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.
return	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`.
since	1.5

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(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:

 this.charAt(k)-anotherString.charAt(k)

If there is no index position at which they differ, then the shorter string lexicographically precedes the longer string. In this case, compareTo returns the difference of the lengths of the strings -- that is, the value:

 this.length()-anotherString.length()

anotherString	the `String` to be compared.
return	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.

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 java.text package provides collators to allow locale-sensitive ordering.

str the String to be compared.

return a negative integer, zero, or a positive integer as the specified String is greater than, equal to, or less than this String, ignoring case considerations.

since 1.2

See also compare(String, String)

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 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`.
return	a string that represents the concatenation of this object's characters followed by the string argument's characters.

public boolean

contains(CharSequence s)
Returns true if and only if this string contains the specified sequence of char values.

s	the sequence to search for
return	true if this string contains `s`, false otherwise
Throws	NullPointerException: if `s` is `null`
since	1.5

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.

sb	The `StringBuffer` to compare this `String` against
return	`true` if this `String` represents the same sequence of characters as the specified `StringBuffer`, `false` otherwise
since	1.4

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.

cs	The sequence to compare this `String` against
return	`true` if this `String` represents the same sequence of char values as the specified sequence, `false` otherwise
since	1.5

public static String

copyValueOf(char[] data, int offset, int count)
Returns a String that represents the character sequence in the array specified.

data	the character array.
offset	initial offset of the subarray.
count	length of the subarray.
return	a `String` that contains the characters of the specified subarray of the character array.

public static String

copyValueOf(char[] data)
Returns a String that represents the character sequence in the array specified.

data	the character array.
return	a `String` that contains the characters of the character array.

public boolean

endsWith(String suffix)
Tests if this string ends with the specified suffix.

suffix	the suffix.
return	`true` if the character sequence represented by the argument is a suffix of the character sequence represented by this object; `false` otherwise. Note that the result will be `true` if the argument is the empty string or is equal to this `String` object as determined by the `#equals(Object)` method.

public 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.

anObject	The object to compare this `String` against
return	`true` if the given object represents a `String` equivalent to this string, `false` otherwise
See also	compareTo(String), equalsIgnoreCase(String)

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)
Applying the method java.lang.Character#toUpperCase(char) to each character produces the same result
Applying the method java.lang.Character#toLowerCase(char) to each character produces the same result

anotherString	The `String` to compare this `String` against
return	`true` if the argument is not `null` and it represents an equivalent `String` ignoring case; `false` otherwise
See also	equals(Object)

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().

format A format string

args Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by the Java Virtual Machine Specification. The behaviour on a null argument depends on the conversion.

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.

Throws NullPointerException: If the format is null

return A formatted string

since 1.5

See also java.util.Formatter

public static String

format(Locale l, String format, Object[] args)
Returns a formatted string using the specified locale, format string, and arguments.

l	The locale to apply during formatting. If `l` is `null` then no localization is applied.
format	A format string
args	Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by the Java Virtual Machine Specification. The behaviour on a `null` argument depends on the conversion.
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
Throws	NullPointerException: If the `format` is `null`
return	A formatted string
since	1.5
See also	java.util.Formatter

public int

hashCode()
Returns a hash code for this string. The hash code for a String object is computed as

 s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]

using 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.)

return

a hash code value for this object.

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:

 this.charAt(k) == ch

is true. For other values of ch, it is the smallest value k such that:

 this.codePointAt(k) == ch

is true. In either case, if no such character occurs in this string, then -1 is returned.

ch	a character (Unicode code point).
return	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.

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:

 (this.charAt(k) == ch) && (k >= fromIndex)

is true. For other values of ch, it is the smallest value k such that:

 (this.codePointAt(k) == ch) && (k >= fromIndex)

is true. In either case, if no such character occurs in this string at or after position 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.

return 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.

public int

indexOf(String str)
Returns the index within this string of the first occurrence of the specified substring. The integer returned is the smallest value k such that:

 this.startsWith(str, k)

is true.

str	any string.
return	if the string argument occurs as a substring within this object, then the index of the first character of the first such substring is returned; if it does not occur as a substring, `-1` is returned.

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 integer returned is the smallest value k for which:

     k >= Math.min(fromIndex, this.length()) && this.startsWith(str, k)

If no such value of k exists, then -1 is returned.

str	the substring for which to search.
fromIndex	the index from which to start the search.
return	the index within this string of the first occurrence of the specified substring, starting at the specified index.

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(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

return a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings.

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:

 this.charAt(k) == ch

is true. For other values of ch, it is the largest value k such that:

 this.codePointAt(k) == ch

is true. In either case, if no such character occurs in this string, then -1 is returned. The String is searched backwards starting at the last character.

ch	a character (Unicode code point).
return	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.

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:

 (this.charAt(k) == ch) && (k <= fromIndex)

is true. For other values of ch, it is the largest value k such that:

 (this.codePointAt(k) == ch) && (k <= fromIndex)

is true. In either case, if no such character occurs in this string at or before position 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.

return 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.

public int

lastIndexOf(String str)
Returns the index within this string of the rightmost occurrence of the specified substring. The rightmost empty string "" is considered to occur at the index value this.length(). The returned index is the largest value k such that

 this.startsWith(str, k)

is true.

str	the substring to search for.
return	if the string argument occurs one or more times as a substring within this object, then the index of the first character of the last such substring is returned. If it does not occur as a substring, `-1` is returned.

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 integer returned is the largest value k such that:

     k <= Math.min(fromIndex, this.length()) && this.startsWith(str, k)

If no such value of k exists, then -1 is returned.

str	the substring to search for.
fromIndex	the index to start the search from.
return	the index within this string of the last occurrence of the specified substring.

public int

length()
Returns the length of this string. The length is equal to the number of Unicode code units in the string.

return

the length of the sequence of characters represented by this object.

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

java.util.regex.Pattern.matches(regex, str)

regex	the regular expression to which this string is to be matched
return	`true` if, and only if, this string matches the given regular expression
Throws	PatternSyntaxException: if the regular expression's syntax is invalid
since	1.4
spec	JSR-51
See also	java.util.regex.Pattern

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.

index	the index to be offset
codePointOffset	the offset in code points
return	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.
since	1.5

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 this String 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)

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.
return	`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)
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 this String object.
ooffset+len is greater than the length of the other argument.
ignoreCase is false and there is some nonnegative integer k less than len such that:
```
 this.charAt(toffset+k) != other.charAt(ooffset+k)
 
```

ignoreCase is true and there is some nonnegative integer k less than len such that:

 Character.toLowerCase(this.charAt(toffset+k)) !=
               Character.toLowerCase(other.charAt(ooffset+k))

and:

 Character.toUpperCase(this.charAt(toffset+k)) !=
         Character.toUpperCase(other.charAt(ooffset+k))

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.
return	`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 String

replace(char oldChar, char newChar)
Returns a new 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 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.
return	a string derived from this string by replacing every occurrence of `oldChar` with `newChar`.

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".

target	The sequence of char values to be replaced
replacement	The replacement sequence of char values
return	The resulting string
Throws	NullPointerException: if `target` or `replacement` is `null`.
since	1.5

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

java.util.regex.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 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 matched

replacement the string to be substituted for each match

return The resulting String

Throws PatternSyntaxException: if the regular expression's syntax is invalid

since 1.4

spec JSR-51

See also java.util.regex.Pattern

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

java.util.regex.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 java.util.regex.Matcher#replaceFirst. Use 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 matched

replacement the string to be substituted for the first match

return The resulting String

Throws PatternSyntaxException: if the regular expression's syntax is invalid

since 1.4

spec JSR-51

See also java.util.regex.Pattern

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.

The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n - 1 times, the array's length will be no greater than n, and the array's last entry will contain all input beyond the last matched delimiter. If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.

The string "boo:and:foo", for example, yields the following results with these parameters:

Regex Limit Result

: 2 { "boo", "and:foo" }

: 5 { "boo", "and", "foo" }

: -2 { "boo", "and", "foo" }

o 5 { "b", "", ":and:f", "", "" }

o -2 { "b", "", ":and:f", "", "" }

o 0 { "b", "", ":and:f" }

An invocation of this method of the form str.split(regex, n) yields the same result as the expression

java.util.regex.Pattern.compile(regex).split(str, n)

regex	the delimiting regular expression
limit	the result threshold, as described above
return	the array of strings computed by splitting this string around matches of the given regular expression
Throws	PatternSyntaxException: if the regular expression's syntax is invalid
since	1.4
spec	JSR-51
See also	java.util.regex.Pattern

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" }

regex	the delimiting regular expression
return	the array of strings computed by splitting this string around matches of the given regular expression
Throws	PatternSyntaxException: if the regular expression's syntax is invalid
since	1.4
spec	JSR-51
See also	java.util.regex.Pattern

public boolean

startsWith(String prefix, int toffset)
Tests if the substring of this string beginning at the specified index starts with the specified prefix.

prefix	the prefix.
toffset	where to begin looking in this string.
return	`true` if the character sequence represented by the argument is a prefix of the substring of this object starting at index `toffset`; `false` otherwise. The result is `false` if `toffset` is negative or greater than the length of this `String` object; otherwise the result is the same as the result of the expression this.substring(toffset).startsWith(prefix)

public boolean

startsWith(String prefix)
Tests if this string starts with the specified prefix.

prefix	the prefix.
return	`true` if the character sequence represented by the argument is a prefix of the character sequence represented by this string; `false` otherwise. Note also that `true` will be returned if the argument is an empty string or is equal to this `String` object as determined by the `#equals(Object)` method.
since	1. 0

public CharSequence

subSequence(int beginIndex, int endIndex)
Returns a new character sequence that is a subsequence of this sequence.

An invocation of this method of the form

 str.subSequence(begin, end)

behaves in exactly the same way as the invocation

 str.substring(begin, end)

This method is defined so that the String class can implement the CharSequence interface.

beginIndex	the begin index, inclusive.
endIndex	the end index, exclusive.
return	the specified subsequence.
Throws	IndexOutOfBoundsException: if `beginIndex` or `endIndex` are negative, if `endIndex` is greater than `length()`, or if `beginIndex` is greater than `startIndex`
since	1.4
spec	JSR-51

public String

substring(int beginIndex)
Returns a new 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)

beginIndex	the beginning index, inclusive.
return	the specified substring.
Throws	IndexOutOfBoundsException: if `beginIndex` is negative or larger than the length of this `String` object.

public String

substring(int beginIndex, int endIndex)
Returns a new 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"

beginIndex	the beginning index, inclusive.
endIndex	the ending index, exclusive.
return	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`.

public char[]

toCharArray()
Converts this string to a new character array.

return

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.

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) capiota capchi captheta capupsil capsigma iota chi theta upsilon sigma lowercased all chars in String

locale use the case transformation rules for this locale

return the String, converted to lowercase.

since 1.1

See also toLowerCase(), toUpperCase(), toUpperCase(Locale)

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 "tıtle", where 'ı' is the LATIN SMALL LETTER DOTLESS I character. To obtain correct results for locale insensitive strings, use toLowerCase(Locale.ENGLISH).

return the String, converted to lowercase.

See also toLowerCase(Locale)

public String

toString()
This object (which is already a string!) is itself returned.

return

the string itself.

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

locale use the case transformation rules for this locale

return the String, converted to uppercase.

since 1.1

See also toUpperCase(), toLowerCase(), toLowerCase(Locale)

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 "TİTLE", where 'İ' is the LATIN CAPITAL LETTER I WITH DOT ABOVE character. To obtain correct results for locale insensitive strings, use toUpperCase(Locale.ENGLISH).

return the String, converted to uppercase.

See also toUpperCase(Locale)

public String

trim()
Returns a copy of the string, with leading and trailing whitespace omitted.

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.

return A copy of this string with leading and trailing white space removed, or this string if it has no leading or trailing white space.

public static String

valueOf(Object obj)
Returns the string representation of the Object argument.

obj	an `Object`.
return	if the argument is `null`, then a string equal to `"null"`; otherwise, the value of `obj.toString()` is returned.
See also	toString()

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 newly created string.

data	a `char` array.
return	a newly allocated string representing the same sequence of characters contained in the character array argument.

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 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.

return a string representing the sequence of characters contained in the subarray of the character array argument.

Throws IndexOutOfBoundsException: if offset is negative, or count is negative, or offset+count is larger than data.length.

public static String

valueOf(boolean b)
Returns the string representation of the boolean argument.

b	a `boolean`.
return	if the argument is `true`, a string equal to `"true"` is returned; otherwise, a string equal to `"false"` is returned.

public static String

valueOf(char c)
Returns the string representation of the char argument.

c	a `char`.
return	a string of length `1` containing as its single character the argument `c`.

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.

i an int.

return a string representation of the int argument.

See also toString(int, int)

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.

l a long.

return a string representation of the long argument.

See also toString(long)

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.

f a float.

return a string representation of the float argument.

See also toString(float)

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.

d a double.

return a string representation of the double argument.

See also toString(double)

Properties

public void

getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)

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

deprecated	This method does not properly convert characters into bytes. As of JDK 1.1, the preferred way to do this is via the `#getBytes()` method, which uses the platform's default charset.
srcBegin	Index of the first character in the string to copy
srcEnd	Index after the last character in the string to copy
dst	The destination array
dstBegin	The start offset in the destination array
Throws	IndexOutOfBoundsException: If any of the following is true: `srcBegin` is negative `srcBegin` is greater than `srcEnd` `srcEnd` is greater than the length of this String `dstBegin` is negative `dstBegin+(srcEnd-srcBegin)` is larger than `dst.length`

public byte[]

getBytes(String charsetName) throws UnsupportedEncodingException
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 java.nio.charset.CharsetEncoder class should be used when more control over the encoding process is required.

charsetName The name of a supported charset

return The resultant byte array

Throws UnsupportedEncodingException: If the named charset is not supported

since JDK1.1

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 java.nio.charset.CharsetEncoder class should be used when more control over the encoding process is required.

charset The java.nio.charset.Charset to be used to encode the String

return The resultant byte array

since 1.6

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 java.nio.charset.CharsetEncoder class should be used when more control over the encoding process is required.

return The resultant byte array

since JDK1.1

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

srcBegin	index of the first character in the string to copy.
srcEnd	index after the last character in the string to copy.
dst	the destination array.
dstBegin	the start offset in the destination array.
Throws	IndexOutOfBoundsException: If any of the following is true: `srcBegin` is negative. `srcBegin` is greater than `srcEnd` `srcEnd` is greater than the length of this string `dstBegin` is negative `dstBegin+(srcEnd-srcBegin)` is larger than `dst.length`

public boolean

isEmpty()
Returns true if, and only if, #length() is 0.

return	`true` if `#length()` is `0`, otherwise `false`
since	1.6

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Java SE 6

version	1.204, 06/09/06
since	JDK1.0
See also	toString(), java.lang.StringBuffer, java.lang.StringBuilder, java.nio.charset.Charset