CS3401 Quiz 1

1) How many times is the following factorial method invoked for complicatedSum(6)?

public int complicatedSum(int n) {
    if (n <= 3)
        return n;
    else if (n % 3 == 0) 
        return n * 3 + complicatedSum(n-1); 
    else if (n % 3 == 2) 
        return n * 2 + complicatedSum(n-1);
    else
        return n + complicatedSum(n-1); 
}

Answer: 4

2) What does recursiveString("abcd") return if that method is defined by the following?

 public String recursiveString(String str) {
      if (str.length() < 2)
          return str;
      return recursiveString(str.substring(1)) +
                          str.substring(str.length()-1);
  }

Answer: dddd

3) What does the following method compute? Assume the method is called initially with i = 0.

public int recursiveEx2(String a, char b, int i) {
    if (i = = a.length( ))
        return 0;
    if (b = = a.charAt(i))
        return recursiveEx2(a, b, i+1) + 1;
    return recursiveEx2(a, b, i+1);
}

Answer: the number of times char b appears in String a

4) What type of argument can the following generic method be passed?

public static <E extends Number> void displayArray(E[] array) {
     for (E element : array)
         System.out.println(element);
}

Answer: an array whose element type is Integer

5) True or False: ArrayList<Comparable> is a subclass of ArrayList<E extends Date>

Answer: False