java string replace character at position

String s = "new String";
String replaced = s.replace("new","Test");
							  ^		 ^
                             old    new char

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

String str = ".............................."; 

        int index = 5; 
  
        char ch = '|'; 
 
        StringBuilder string = new StringBuilder(str); 
        string.setCharAt(index, ch); 

        System.out.println(string);