Class String

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.

The Java language provides special support for the string concatentation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuffer class and its append method. String conversions are implemented through the method toString, defined by Object and inherited by all classes in Java.

String constructors
String()	Initializes a newly created String object so that it represents an empty character sequence.
Convert array of byte to String
String(byte[] bytes)	Construct a new String by converting the specified array of bytes using the platform's default character encoding.
String(byte[] bytes, int offset, int length)	Construct a new String by converting the specified subarray of bytes using the platform's default character encoding.
Convert array of char to String
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.
Convert existing String to new instance
String(String value)	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.
Convert StringBuffer to String
String(StringBuffer buffer)	Allocates a new string that contains the sequence of characters currently contained in the string buffer argument.

String methods
char charAt(int index)	Returns the character at the specified index.
String concat(String str)	Concatenates the specified string to the end of this string.
int length()	Returns the length of this string.
String replace(char oldChar, char newChar)	Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.
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.
Comparisons
int compareTo(Object o)	Compares this String to another Object.
int compareTo(String anotherString)	Compares two strings lexicographically.
int compareToIgnoreCase(String str)	Compares two strings lexicographically, ignoring case considerations.
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.
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.
boolean startsWith(String prefix)	Tests if this string starts with the specified prefix.
boolean startsWith(String prefix, int toffset)	Tests if this string starts with the specified prefix beginning a specified index.
Searching
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.
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 rightmost 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.
Conversions
static String copyValueOf(char[] data)	Returns a String that is equivalent to the specified character array.
static String copyValueOf(char[] data, int offset, int count)	Returns a String that is equivalent to the specified character array.
byte[] getBytes()	Convert this String into bytes according to the platform's default character encoding, storing the result into a new byte array.
void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)	Copies characters from this string into the destination character array.
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, which is returned by Locale.getDefault.
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, which is returned by Locale.getDefault.
String trim()	Removes white space from both ends of this string.
static String valueOf(X)	Returns the string representation of the argument X. type of X = boolean, char, char[], double, float, int, long, Object