how to replace a character at a particular index java code example

Example 1: java string replace character at position

String str = in.nextLine();	//Original String
char cr = in.next().charAt(0); // character to replace
int index = in.nextInt();	// Index where replaced
str = str.substring(0, index) + cr + str.substring(index + 1);// modified string

Example 2: how to replace a character with another character in a string in java

public class JavaExample{
   public static void main(String args[]){
	String str = new String("Site is BeginnersBook.com");

	System.out.print("String after replacing com with net :" );
	System.out.println(str.replaceFirst("com", "net"));

	System.out.print("String after replacing Site name:" );
	System.out.println(str.replaceFirst("Beginners(.*)", "XYZ.com"));
   }
}