Android java object to string

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:

is equivalent to:

Here are some more examples of how strings can be used:

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).

Field Summary

Fields

Modifier and Type	Field and Description
static Comparator	CASE_INSENSITIVE_ORDER

Constructor Summary

Constructors

Constructor and Description
String()

String(byte[] bytes, Charset charset) String(byte[] ascii, int hibyte) String(byte[] bytes, int offset, int length) String(byte[] bytes, int offset, int length, Charset charset) String(byte[] ascii, int hibyte, int offset, int count) String(byte[] bytes, int offset, int length, String charsetName) String(byte[] bytes, String charsetName) String(char[] value, int offset, int count) String(int[] codePoints, int offset, int count)

Method Summary

Methods

Modifier and Type	Method and Description
char	charAt(int index)

int codePointCount(int beginIndex, int endIndex) int compareTo(String anotherString) static String copyValueOf(char[] data) static String copyValueOf(char[] data, int offset, int count) boolean endsWith(String suffix) boolean equals(Object anObject) boolean equalsIgnoreCase(String anotherString) static String format(Locale l, String format, Object. args) static String format(String format, Object. args) void getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin) byte[] getBytes(String charsetName) void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) int indexOf(int ch, int fromIndex) int indexOf(String str, int fromIndex) int lastIndexOf(int ch, int fromIndex) int lastIndexOf(String str, int fromIndex) boolean matches(String regex) int offsetByCodePoints(int index, int codePointOffset) boolean regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len) boolean regionMatches(int toffset, String other, int ooffset, int len) String replace(char oldChar, char newChar) String replace(CharSequence target, CharSequence replacement) String replaceAll(String regex, String replacement) String replaceFirst(String regex, String replacement) String[] split(String regex, int limit) boolean startsWith(String prefix) boolean startsWith(String prefix, int toffset) CharSequence subSequence(int beginIndex, int endIndex) String substring(int beginIndex, int endIndex) static String valueOf(boolean b) static String valueOf(char c) static String valueOf(char[] data) static String valueOf(char[] data, int offset, int count) static String valueOf(double d) static String valueOf(float f) static String valueOf(int i) static String valueOf(long l)

Methods inherited from class java.lang.Object

Field Detail

CASE_INSENSITIVE_ORDER

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

String

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.

String

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

String

This method always replaces malformed-input and unmappable-character sequences with this charset’s default replacement string. The CharsetDecoder class should be used when more control over the decoding process is required.

String

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

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.

Method Detail

length

isEmpty

charAt

If the char value specified by the index is a surrogate, the surrogate value is returned.

codePointAt

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.

codePointBefore

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.

codePointCount

offsetByCodePoints

getChars

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:

getBytes

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:

getBytes

The behavior of this method when this string cannot be encoded in the given charset is unspecified. The CharsetEncoder class should be used when more control over the encoding process is required.

getBytes

This method always replaces malformed-input and unmappable-character sequences with this charset’s default replacement byte array. The CharsetEncoder class should be used when more control over the encoding process is required.

getBytes

The behavior of this method when this string cannot be encoded in the default charset is unspecified. The CharsetEncoder class should be used when more control over the encoding process is required.

equals

contentEquals

equalsIgnoreCase

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

compareTo

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 compareTo returns the difference of the two character values at position k in the two string — that is, the value:

compareToIgnoreCase

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.

regionMatches

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)

regionMatches

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:

startsWith

endsWith

hashCode

indexOf

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:

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).

lastIndexOf

All indices are specified in char values (Unicode code units).

indexOf

The returned index is the smallest value k for which:

indexOf

The returned index is the smallest value k for which:

lastIndexOf

The returned index is the largest value k for which:

lastIndexOf

The returned index is the largest value k for which:

substring

subSequence

An invocation of this method of the form

concat

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.

replace

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 .

matches

An invocation of this method of the form str.matches(regex) yields exactly the same result as the expression

contains

replaceFirst

An invocation of this method of the form str.replaceFirst(regex, repl) yields exactly the same result as the expression

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceFirst(java.lang.String) . Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

replaceAll

An invocation of this method of the form str.replaceAll(regex, repl) yields exactly the same result as the expression

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll . Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

replace

split

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
: 5
: -2
o 5
o -2
o 0

Regex	Limit	Result
:	2
:	5
:	-2
o	5
o	-2
o	0

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

split

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

:
o

Regex	Result
:
o

toLowerCase

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

toLowerCase

Note: This method is locale sensitive, and may produce unexpected results if used for strings that are intended to be interpreted locale independently. Examples are programming language identifiers, protocol keys, and HTML tags. For instance, «TITLE».toLowerCase() in a Turkish locale returns «t\u0131tle» , where ‘\u0131’ is the LATIN SMALL LETTER DOTLESS I character. To obtain correct results for locale insensitive strings, use toLowerCase(Locale.ENGLISH) .

toUpperCase

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

toUpperCase

Note: This method is locale sensitive, and may produce unexpected results if used for strings that are intended to be interpreted locale independently. Examples are programming language identifiers, protocol keys, and HTML tags. For instance, «title».toUpperCase() in a Turkish locale returns «T\u0130TLE» , where ‘\u0130’ is the LATIN CAPITAL LETTER I WITH DOT ABOVE character. To obtain correct results for locale insensitive strings, use toUpperCase(Locale.ENGLISH) .

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.

toString

toCharArray

format

The locale always used is the one returned by Locale.getDefault() .

format

valueOf

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.

copyValueOf

valueOf

The representation is exactly the one returned by the Integer.toString method of one argument.

valueOf

The representation is exactly the one returned by the Long.toString method of one argument.

valueOf

The representation is exactly the one returned by the Float.toString method of one argument.

valueOf

The representation is exactly the one returned by the Double.toString method of one argument.

intern

A pool of strings, initially empty, is maintained privately by the class String .

When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned.

It follows that for any two strings s and t , s.intern() == t.intern() is true if and only if s.equals(t) is true .

All literal strings and string-valued constant expressions are interned. String literals are defined in section 3.10.5 of the The Java™ Language Specification .

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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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Источник

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