StringBuffer setCharAt() method in Java with Examples

The setCharAt() method of StringBuffer class sets the character at the position index to character which is the value passed as parameter to method. This method returns a new sequence which is identical to old sequence only difference is a new character ch is present at position index in new sequence. The index argument must be greater than or equal to 0, and less than the length of the String contained by StringBuffer object. Syntax:

public void setCharAt(int index, char ch)

Parameters: This method takes two parameters:

• index: Integer type value which refers to the index of character to be set.
• ch: Character type value which refers to the new char.

Returns: This method returns nothing. Exception: This method throws IndexOutOfBoundException if the index is negative or greater than length(). Below programs demonstrate the setCharAt() method of StringBuffer Class Example 1: Java

// Java program to demonstrate
// the setCharAt() Method.
class GFG {
    public static void main(String[] args)
    {
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer str
            = new StringBuffer("Geeks For Geeks");
        // print string
        System.out.println("String = "
                           + str.toString());
        // set char at index 4 to '0'
        str.setCharAt(7, '0');
        // print string
        System.out.println("After setCharAt() String = "
                           + str.toString());
    }
}

Example 2: To demonstrate IndexOutOfBoundsException. Java

// Java program to demonstrate
// Exception thrown by the setCharAt() Method.
class GFG {
    public static void main(String[] args)
    {
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer str
            = new StringBuffer("Geeks for Geeks");
        try {
            // pass index -1
            str.setCharAt(-1, 'T');
        }
        catch (Exception e) {
            System.out.println("Exception:" + e);
        }
    }
}

References: https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuffer.html#setCharAt(int, char)