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As per the name of the method goes, charAt() method of String class is used to determine a character at a particular index in a string.

Signature of charAt()

public char charAt(int index)

• Access modifier - charAt() method is a public method,
• Parameter passed - An int index is passed to this method
• Value returned - This method returns an char value, present at a particular index in the String object.

Note

When calling charAt() method, the first index in a String object is counted as 0.

Calling charAt() to extract a char at a particular index in a String.

Here in the upcoming code, we have initialized a Sring object with a value and we are calling charAt() method to determine the character present at a particular index in this String object.

// Program to find a character at a particular index of a String.


class StringCharAt
{
public static void main(String[] ar)
{
String str= new String("Keep Smiling");
System.out.println("Original String is "+ str);

//Searching for a character at index 0 in String
char c = str.charAt(0);

System.out.println("character at the index 2 of "+ str + " is " + c);

//Searching for a character at index 5 in String
c = str.charAt(4);

System.out.println("character at the index 4 of "+ str + " is " + c);

//Searching for a character at index 5 in String
c = str.charAt(7);

System.out.println("character at the index 7 of "+ str + " is " + c);
}
}

Output is :

Original String is Keep Smiling
character at the index 2 of Keep Smiling is K
character at the index 4 of Keep Smiling is 
character at the index 7 of Keep Smiling is i

Program Analysis

In the code, we have initialized a string str with a value Keep Smiling
• Character present at the index 2 is extracted by calling chatAt(2) on the String, returns - K
• Character present at the index 4 is extracted by calling chatAt(4) on the String, is an empty space.
• Character present at the index 7 is extracted by calling chatAt(7) on the String, returns - i

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Exception in calling chatAt() method.

Here in the next code, an Exception is raised when we are trying to determine a character at an out-of-range index in the String object..

// Program to find a character at a particular index of a String.


class StringCharAt
{
public static void main(String[] ar)
{
String str= new String("Mexico");

//Searching a character at index 9.
char c = str.charAt(9);

System.out.println("Original String is "+ str);
System.out.println("Character at the index 9 of "+ str + " is " + c);
}
}

Output is :

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 9
        at java.lang.String.charAt(Unknown Source)
        at StringCharAt.main(StringCharAt.java:11)

Program Analysis

• In this code above, an Exception of type StringIndexOutOfBoundsException is raised when trying to find a character at an out-of-range index, 9 in the String object which is initialized to the value Mexico.

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