What you need to do: Write and test the following 2 overloaded methods: //precondition: ch.length() == 1 public static String setChar(String str, int index, String ch) public static String setChar (String str, int index, char ch) This overloaded method should return a new String containing the result when the character at position index in str has been replaced by ch. For example, the code: String word "touch"; System.out.println(word); word setChar (word, 3, "g"); System.out.println(word); word setChar (word, 0, 'r'); System.out.println(word); //calls String version //calls char version word setChar (word, 4, (char) (word.charAt (4)-3));//calls char version System.out.println(word); would output touch tough rough rouge If you know how the substring method works, you can use that. Otherwise, I would suggest calling the toCharArray() method on str to convert it to an array of char, changing the appropriate character, and then using the String constructor to convert the array back to a new String before returning it. Don't forget, it is quite legal to do one of your two methods by calling the other one.