1. indexOf():

                                                                   indexOf():
This method is used to search a character or a string within the string.

There are two forms of this function:

                        indexOf(int ch)

                        indexOf(String s)

Where:

            ch specify the ASCII  value of the character which we want to search

            s will be the substring which you want to search

The function returns the index number of the first match and if no match occurs then the method will return -1

 Example:       

String s="this is the very fine day";

System.out.println(s.indexOf('t'));

System.out.println(s.indexOf("that"));

System.out.println(s.indexOf("the"));

 Output :

0

-1

8

There is another form also which can be used for searching the multiple occurrences of a single character or a string.            

indexOf(int ch,int sindex)

indexOf(String s,int sindex)

Where:

                        sindex specify the index position from where we want to start the searching

Example:

String s="this is a matrix . this is cool";

System.out.println(s.indexOf("this"));

System.out.println(s.indexOf("this",0));

System.out.println(s.indexOf("this",2));

Output:

0

0

18