String (Java Platform SE 7 )

java.lang.Object
- java.lang.String

All Implemented Interfaces:

Serializable, CharSequence, Comparable<String>
```
public final class String
extends Object
implements Serializable, Comparable<String>, 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).
Since:

JDK1.0

See Also:
Object.toString(), StringBuffer, StringBuilder, Charset, Serialized Form

Field Summary

Fields
Modifier and Type Field and Description

static Comparator<String> CASE_INSENSITIVE_ORDER
A Comparator that orders String objects as by compareToIgnoreCase.

Fields
Modifier and Type	Field and Description
`static Comparator<String>`	`CASE_INSENSITIVE_ORDER` A Comparator that orders `String` objects as by `compareToIgnoreCase`.

Constructor Summary

Constructors
Constructor and Description
`String()` Initializes a newly created `String` object so that it represents an empty character sequence.
`String(byte[] bytes)` Constructs a new `String` by decoding the specified array of bytes using the platform's default charset.
`String(byte[] bytes, Charset charset)` Constructs a new `String` by decoding the specified array of bytes using the specified charset.
`String(byte[] ascii, int hibyte)` Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the `String` constructors that take a `Charset`, charset name, or that use the platform's default charset.
`String(byte[] bytes, int offset, int length)` Constructs a new `String` by decoding the specified subarray of bytes using the platform's default charset.
`String(byte[] bytes, int offset, int length, Charset charset)` Constructs a new `String` by decoding the specified subarray of bytes using the specified charset.
`String(byte[] ascii, int hibyte, int offset, int count)` Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the `String` constructors that take a `Charset`, charset name, or that use the platform's default charset.
`String(byte[] bytes, int offset, int length, String charsetName)` Constructs a new `String` by decoding the specified subarray of bytes using the specified charset.
`String(byte[] bytes, String charsetName)` Constructs a new `String` by decoding the specified array of bytes using the specified charset.
`String(char[] value)` Allocates a new `String` so that it represents the sequence of characters currently contained in the character array argument.
`String(char[] value, int offset, int count)` Allocates a new `String` that contains characters from a subarray of the character array argument.
`String(int[] codePoints, int offset, int count)` Allocates a new `String` that contains characters from a subarray of the Unicode code point array argument.
`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.
`String(StringBuffer buffer)` Allocates a new string that contains the sequence of characters currently contained in the string buffer argument.
`String(StringBuilder builder)` Allocates a new string that contains the sequence of characters currently contained in the string builder argument.

Method Summary

Methods
Modifier and Type	Method and Description
`char`	`charAt(int index)` Returns the `char` value at the specified index.
`int`	`codePointAt(int index)` Returns the character (Unicode code point) at the specified index.
`int`	`codePointBefore(int index)` Returns the character (Unicode code point) before the specified index.
`int`	`codePointCount(int beginIndex, int endIndex)` Returns the number of Unicode code points in the specified text range of this `String`.
`int`	`compareTo(String anotherString)` Compares two strings lexicographically.
`int`	`compareToIgnoreCase(String str)` Compares two strings lexicographically, ignoring case differences.
`String`	`concat(String str)` Concatenates the specified string to the end of this string.
`boolean`	`contains(CharSequence s)` Returns true if and only if this string contains the specified sequence of char values.
`boolean`	`contentEquals(CharSequence cs)` Compares this string to the specified `CharSequence`.
`boolean`	`contentEquals(StringBuffer sb)` Compares this string to the specified `StringBuffer`.
`static String`	`copyValueOf(char[] data)` Returns a String that represents the character sequence in the array specified.
`static String`	`copyValueOf(char[] data, int offset, int count)` Returns a String that represents the character sequence in the array specified.
`boolean`	`endsWith(String suffix)` Tests if this string ends with the specified suffix.
`boolean`	`equals(Object anObject)` Compares this string to the specified object.
`boolean`	`equalsIgnoreCase(String anotherString)` Compares this `String` to another `String`, ignoring case considerations.
`static String`	`format(Locale l, String format, Object... args)` Returns a formatted string using the specified locale, format string, and arguments.
`static String`	`format(String format, Object... args)` Returns a formatted string using the specified format string and arguments.
`byte[]`	`getBytes()` Encodes this `String` into a sequence of bytes using the platform's default charset, storing the result into a new byte array.
`byte[]`	`getBytes(Charset charset)` Encodes this `String` into a sequence of bytes using the given charset, storing the result into a new byte array.
`void`	`getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)` 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.
`byte[]`	`getBytes(String charsetName)` Encodes this `String` into a sequence of bytes using the named charset, storing the result into a new byte array.
`void`	`getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)` Copies characters from this string into the destination character array.
`int`	`hashCode()` Returns a hash code for this string.
`int`	`indexOf(int ch)` Returns the index within this string of the first occurrence of the specified character.
`int`	`indexOf(int ch, int fromIndex)` Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index.
`int`	`indexOf(String str)` Returns the index within this string of the first occurrence of the specified substring.
`int`	`indexOf(String str, int fromIndex)` Returns the index within this string of the first occurrence of the specified substring, starting at the specified index.
`String`	`intern()` Returns a canonical representation for the string object.
`boolean`	`isEmpty()` Returns `true` if, and only if, `length()` is `0`.
`int`	`lastIndexOf(int ch)` Returns the index within this string of the last occurrence of the specified character.
`int`	`lastIndexOf(int ch, int fromIndex)` Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index.
`int`	`lastIndexOf(String str)` Returns the index within this string of the last occurrence of the specified substring.
`int`	`lastIndexOf(String str, int fromIndex)` Returns the index within this string of the last occurrence of the specified substring, searching backward starting at the specified index.
`int`	`length()` Returns the length of this string.
`boolean`	`matches(String regex)` Tells whether or not this string matches the given regular expression.
`int`	`offsetByCodePoints(int index, int codePointOffset)` Returns the index within this `String` that is offset from the given `index` by `codePointOffset` code points.
`boolean`	`regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)` Tests if two string regions are equal.
`boolean`	`regionMatches(int toffset, String other, int ooffset, int len)` Tests if two string regions are equal.
`String`	`replace(char oldChar, char newChar)` Returns a new string resulting from replacing all occurrences of `oldChar` in this string with `newChar`.
`String`	`replace(CharSequence target, CharSequence replacement)` Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence.
`String`	`replaceAll(String regex, String replacement)` Replaces each substring of this string that matches the given regular expression with the given replacement.
`String`	`replaceFirst(String regex, String replacement)` Replaces the first substring of this string that matches the given regular expression with the given replacement.
`String[]`	`split(String regex)` Splits this string around matches of the given regular expression.
`String[]`	`split(String regex, int limit)` Splits this string around matches of the given regular expression.
`boolean`	`startsWith(String prefix)` Tests if this string starts with the specified prefix.
`boolean`	`startsWith(String prefix, int toffset)` Tests if the substring of this string beginning at the specified index starts with the specified prefix.
`CharSequence`	`subSequence(int beginIndex, int endIndex)` Returns a new character sequence that is a subsequence of this sequence.
`String`	`substring(int beginIndex)` Returns a new string that is a substring of this string.
`String`	`substring(int beginIndex, int endIndex)` Returns a new string that is a substring of this string.
`char[]`	`toCharArray()` Converts this string to a new character array.
`String`	`toLowerCase()` Converts all of the characters in this `String` to lower case using the rules of the default locale.
`String`	`toLowerCase(Locale locale)` Converts all of the characters in this `String` to lower case using the rules of the given `Locale`.
`String`	`toString()` This object (which is already a string!) is itself returned.
`String`	`toUpperCase()` Converts all of the characters in this `String` to upper case using the rules of the default locale.
`String`	`toUpperCase(Locale locale)` Converts all of the characters in this `String` to upper case using the rules of the given `Locale`.
`String`	`trim()` Returns a copy of the string, with leading and trailing whitespace omitted.
`static String`	`valueOf(boolean b)` Returns the string representation of the `boolean` argument.
`static String`	`valueOf(char c)` Returns the string representation of the `char` argument.
`static String`	`valueOf(char[] data)` Returns the string representation of the `char` array argument.
`static String`	`valueOf(char[] data, int offset, int count)` Returns the string representation of a specific subarray of the `char` array argument.
`static String`	`valueOf(double d)` Returns the string representation of the `double` argument.
`static String`	`valueOf(float f)` Returns the string representation of the `float` argument.
`static String`	`valueOf(int i)` Returns the string representation of the `int` argument.
`static String`	`valueOf(long l)` Returns the string representation of the `long` argument.
`static String`	`valueOf(Object obj)` Returns the string representation of the `Object` argument.

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - CASE_INSENSITIVE_ORDER
```
public static final Comparator<String> CASE_INSENSITIVE_ORDER
```
    A Comparator that orders String objects as by compareToIgnoreCase. This comparator is serializable.
    Note that this Comparator does not take locale into account, and will result in an unsatisfactory ordering for certain locales. The java.text package provides Collators to allow locale-sensitive ordering.
    
    Since:
    
    1.2
    
    See Also:
    Collator.compare(String, String)
- Constructor Detail
  - String
```
public String()
```
    Initializes a newly created String object so that it represents an empty character sequence. Note that use of this constructor is unnecessary since Strings are immutable.
  - String
```
public String(String original)
```
    Initializes a newly created String object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string. Unless an explicit copy of original is needed, use of this constructor is unnecessary since Strings are immutable.
    
    Parameters:
    original - A String
  - String
```
public String(char[] value)
```
    Allocates a new String so that it represents the sequence of characters currently contained in the character array argument. The contents of the character array are copied; subsequent modification of the character array does not affect the newly created string.
    
    Parameters:
    value - The initial value of the string
  - String
```
public String(char[] value,
      int offset,
      int count)
```
    Allocates a new String that contains characters from a subarray of the character array argument. The offset argument is the index of the first character of the subarray and the count argument specifies the length of the subarray. The contents of the subarray are copied; subsequent modification of the character array does not affect the newly created string.
    
    Parameters:
    value - 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
  - String
```
public String(int[] codePoints,
      int offset,
      int count)
```
    Allocates a new String that contains characters from a subarray of the Unicode code point array argument. The offset argument is the index of the first code point of the subarray and the count argument specifies the length of the subarray. The contents of the subarray are converted to chars; subsequent modification of the int array does not affect the newly created string.
    
    Parameters:
    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
    
    IndexOutOfBoundsException - If the offset and count arguments index characters outside the bounds of the codePoints array
    Since:
    
    1.5
  - String
```
@Deprecated
public String(byte[] ascii,
                 int hibyte,
                 int offset,
                 int count)
```
    Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the String constructors that take a Charset, charset name, or that use the platform's default charset.
    
    Allocates a new String constructed from a subarray of an array of 8-bit integer values.
    The offset argument is the index of the first byte of the subarray, and the count argument specifies the length of the subarray.
    Each byte in the subarray is converted to a char as specified in the method above.
    
    Parameters:
    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[])
  - String
```
@Deprecated
public String(byte[] ascii,
                 int hibyte)
```
    Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the String constructors that take a Charset, charset name, or that use the platform's default charset.
    Allocates a new String containing characters constructed from an array of 8-bit integer values. Each character cin the resulting string is constructed from the corresponding component b in the byte array such that:
    c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
    Parameters:
    ascii - 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),

Class String

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

CASE_INSENSITIVE_ORDER

Constructor Detail

String

String

String

String

String

String

String