Java string.indexOf() to get position of a matching string or char inside the input string

string.indexOf() Returns the position of the matching string or char from left.
Syntax

string.indexOf(input,startPos)

input : Can be char or string.
startPos : (optional ) Int position from where the matching will start

Java String indexOf()

Note these points
Matching position is always returned from left, first position is 0 ( zero ).
First occurrence is returned ( from startPos index if given ) .
Search starts from 0 position if startPos is not given.

Using char input

String my_str="Welcome to plus2net.com";
System.out.println(my_str.indexOf("2"));// 15
System.out.println(my_str.indexOf("e"));// 1

Using char and startPos

String my_str="Welcome to plus2net.com";
System.out.println(my_str.indexOf("e",1));// 1 
System.out.println(my_str.indexOf("e",2));// 6

Using string input

String my_str="Welcome to plus2net.com";
System.out.println(my_str.indexOf("co"));// 3

Using string and startPos

String my_str="Welcome to plus2net.com";
System.out.println(my_str.indexOf("co",3));// 3
System.out.println(my_str.indexOf("co",4));// 20
System.out.println(my_str.indexOf("com",4));// 20

Getting position of @ and . inside a email address.

System.out.println("userid@example.com".indexOf("@"));// 6
System.out.println("userid@example.com".indexOf("."));// 14

Difference between indexOf() and lastIndexOf()

These pictures shows the difference between indexOf() and lastIndexOf()

Java String indexOf()

All String functions

lastIndexOf() codePointAt() codePointBefore() compareTo() Java - Tutorials

string.indexOf()

Difference between indexOf() and lastIndexOf()

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