/*Given a non-empty string and an int n, return a new string where the char 
at index n has been removed. The value of n will be a valid index of a char 
in the original string i.e. n will be in the range 0..str.length()-1 inclusive).*/

public String missingChar(String str, int n) {
    return (str.substring(0,n) + str.substring(n+1, str.length()));
}