[API] java.lang.String

java.lang

Class String

• 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.

  • 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)