In Java, string is basically an object that represents sequence of char values. In java, objects of String are immutable which means a constant and cannot be changed once created.
The java.lang.String class is used to create a
string object.
There are two ways to create String object:
- By string literal
Java
String literal is created by using double quotes.
String s="welcome";
To make
Java more memory efficient String literals are used (because no new objects are
created if it exists already in the string constant pool).
- By new keyword
String s=new String("welcome");
In this
case, JVM will create a new string object in normal (non-pool) heap
memory, and the literal "Welcome" will be placed in the string
constant pool. The variable s will refer to the object in a heap (non-pool).
Example:
public class StringEx{
public static void main(String args[]){
String s1="java";
char ch[]={'s','t','r','i','n','g','s'};
String s2=new String(ch); //converting char array to
string
String s3=new String("example"); //creating
Java string by new keyword
System.out.println(s1);
System.out.println(s2);
System.out.println(s3);
}}
The java.lang.String class provides many useful
methods to perform operations on sequence of char values.
Method |
Description |
Return
Type |
Returns the character at the specified index
(position) |
char |
|
Returns the Unicode of the character at the
specified index |
int |
|
Returns the Unicode of the character before the
specified index |
int |
|
Returns the Unicode in the specified text range of
this String |
int |
|
Compares two strings lexicographically |
int |
|
Compares two strings lexicographically, ignoring
case differences |
int |
|
Appends a string to the end of another string |
String |
|
Checks whether a string contains a sequence of
characters |
boolean |
|
Checks whether a string contains the exact same
sequence of characters of the specified CharSequence or StringBuffer |
boolean |
|
Returns a String that represents the characters of
the character array |
String |
|
Checks whether a string ends with the specified
character(s) |
boolean |
|
Compares two strings. Returns true if the strings
are equal, and false if not |
boolean |
|
Compares two strings, ignoring case considerations |
boolean |
|
format() |
Returns a formatted string using the specified
locale, format string, and arguments |
String |
getBytes() |
Encodes this String into a sequence of bytes using
the named charset, storing the result into a new byte array |
byte[] |
getChars() |
Copies characters from a string to an array of
chars |
void |
Returns the hash code of a string |
int |
|
Returns the position of the first found occurrence
of specified characters in a string |
int |
|
intern() |
Returns the canonical representation for the
string object |
String |
Checks whether a string is empty or not |
boolean |
|
Returns the position of the last found occurrence
of specified characters in a string |
int |
|
Returns the length of a specified string |
int |
|
matches() |
Searches a string for a match against a regular
expression, and returns the matches |
boolean |
offsetByCodePoints() |
Returns the index within this String that is
offset from the given index by codePointOffset code points |
int |
regionMatches() |
Tests if two string regions are equal |
boolean |
replace() |
Searches a string for a specified value, and
returns a new string where the specified values are replaced |
String |
replaceFirst() |
Replaces the first occurrence of a substring that
matches the given regular expression with the given replacement |
String |
replaceAll() |
Replaces each substring of this string that
matches the given regular expression with the given replacement |
String |
split() |
Splits a string into an array of substrings |
String[] |
Checks whether a string starts with specified
characters |
boolean |
|
subSequence() |
Returns a new character sequence that is a
subsequence of this sequence |
CharSequence |
substring() |
Returns a new string which is the substring of a
specified string |
String |
toCharArray() |
Converts this string to a new character array |
char[] |
Converts a string to lower case letters |
String |
|
toString() |
Returns the value of a String object |
String |
Converts a string to upper case letters |
String |
|
Removes whitespace from both ends of a string |
String |
|
valueOf() |
Returns the string representation of the specified
value |
String |
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