[Eranga]

Here is a the solution in the first way that Fubarable explain,

Code:

        Scanner scn = new Scanner(System.in);
        String result = null;
        
        System.out.println("Enter the value: ");
        String str = scn.nextLine();
        
        if(str.length() == 1)
            result = str + "0";
        else 
            result = str.substring(0, (str.length() - 2)) + 
                    str.charAt(str.length() - 1) + str.charAt(str.length() - 2);