What is String in java
String is a collection of characters but in this language string is an object which represents a collection of characters. To create string object String class is used. An array of characters is known as String.
Create Strings
String name = “intellipaat”; OR
char[] name={'i','n','t','e','l','l','i','p','a','a',’t’};
The java.lang.String class implements Serializable, Comparable and CharSequence interfaces.
The java String is immutable i.e. it cannot be changed but a new instance is created. For mutable class, you can use StringBuffer and StringBuilder class.
There are two ways to create String object:
- By string literal
- By new keyword
1. By String Literal
It is created by using double quotes. The area in which string objects are stored is known as string constant pool.
e.g.
String name="intellipaat";
2. By new keyword
There is another way to create string object using new keyword like as follows:
String name=newString("intellipaat");
Java String class methods
The java.lang.String class contains number of methods which are used to perform various operations:
| Method |
Description |
| int length() |
Returns string length |
| char charAt(int index) |
Returns char value for the specified index |
| static String format(String format, Object… args) |
Returns formatted string |
| String substring(int StartingIndex) |
Returns substring for given start index |
| String substring(int StartingIndex, int EndingIndex) |
Returns substring for given start index and end index |
| boolean contains(CharSequence s) |
Returns true or false after matching the sequence of char value |
| boolean equals(Object another) |
Check the equality of string with object |
| String toLowerCase() |
Returns string in lowercase. |
| String toUpperCase() |
Returns string in uppercase. |
| boolean isEmpty() |
Check string is empty or not. If yes than return true otherwise false |
| String trim() |
Returns trimmed string omitting leading and trailing spaces |
| String replace(char old_character , char new_character) |
Replaces all occurrences of specified char value |
| String replace(CharSequence old, CharSequence new) |
Replaces all occurrences of specified CharSequence |
| String split(String regex) |
Returns splitted string matching regex |
| int indexOf(int ch) |
Returns specified char value index |
| int indexOf(int ch, int fromIndex) |
Returns specified char value index starting with given index |
| int indexOf(String substring) |
Returns specified substring index |
| int indexOf(String substring, int fromIndex) |
Returns specified substring index starting with given index |