indexOf() & lastIndexOf()

indexOf()

The Java String class indexOf() method returns the position of the first occurrence of the specified character or string in a specified string. If it is not found, it returns -1. The index counter starts from zero.

Usage and examples :

 String s = "Hello World. Hello Java.";
 //find index of H from the beginning of the String
 int a = s.indexOf('H'); //  0
 //find indexOf('H') from index 1 of the string
 int b = s.indexOf('H' , 1); // 13
 //find index of the given substring
 int c = s.indexOf("Hello"); // 0
 //find index of the given substring starting from index 1
 int d = s.indexOf("Hello" , 1); // 13
 //find index of h outside the length of string/character not present
 int e = s.indexOf('H' , s.length()); // -1

lastIndexOf()

The Java String class lastIndexOf() method returns the last index of the given character value or substring. If it is not found, it returns -1. The index counter starts from zero.

Usage and examples :

 String s = "Hello World. Hello Java.";
 
 int a = s.lastIndexOf('H'); //  13
 int b = s.lastIndexOf('H' , 1); // 13
 int c = s.lastIndexOf("Hello"); // 13
 int d = s.lastIndexOf("Hello" , 1); // 13
 int e = s.lastIndexOf('H' , s.length()); // -1

`.indexOf()` vs `.lastIndexOf()`

Similarities

• Both the indexOf() method and the lastIndexOf() method returns int values.
  
• Both return -1 when required charcter is not present within the specified string or within the specified search space of the specified string.

Difference

• The Java string indexOf() method returns a int value corresponding to the first occurance of the given character or substring in a specified string whereas lastIndexOf() method returns a int value corresponding to the last occurance of the given character or substring in a specified string.