What is Java charAt method?

The charAt(int) method returns the character in the specified string for given index number. The index of string starts at zero.

For example, consider this string:

“Hello World Java”

You want to know the character at 6th index position in that string by using charAt method.

Syntax of using charAt Java method

public char charAt(int index)

A few points about the string charAt method:

  • The charAt takes an argument which is an int type.
  • The method returns the character as char for the given int argument. The int value specifies the index that starts at 0.
  • The index range must be between 0 to the length of string -1.
  • If the index value is greater than string length or a negative number, an error IndexOutOfBoundsException occurs.
  • The charAt method is specified by CharSequence.

The example of using charAt method

In the following example, Java charAt method is used to return the character in a string. I will use the same string as in introductory section. Let us see which characters occur at the index 6 and 12:

See online demo and code

The output:

Java charAt string

A program to tell if certain characters exist in a string?

By using charAt method, this program will output if a vowel character occurs at the start of the specified string. For that, a string is entered by the user and program will check for these characters. For taking the user input, the Scanner class is used:

See the output of the tried strings:

What if given index is greater than the length of string?

As mentioned earlier, if you provide a negative number or greater than the string length then an error occurs:

See online demo and code

charAt string error

You saw, for the index 15, program generated StringIndexOutOfBoundsException error with the description: String index out of range: 15.

The indexOf method

The indexOf method returns the index number of the given character in specified string. For example, if we have a string:

“indexOf method in Java”

This is how you may use the indexOf method for getting ‘J’ index number:

x = str.indexOf(‘J’);

The example program:

The output:

The indexOf ‘J’ is: 18

Learn more about indexOf method with details – Java indexOf method