In order to understand the error in this code, you must understand what the loop is doing. It is assigning variable types to the array of Object objects based upon the remainder of dividing the loop control variable i by 4. You thus get a repeating pattern:

Integer, String, Double, String, Integer, String, Double, String, . . .

Now, index 8 will be an Integer (for it has a remainder of 0). This means that when you do the type cast to a String, you will receive a TypeCastException for the line reading:

String s = (String)objects[8];

At this point of the code, it is not possible for a or b to be null. Furthermore, these arrays cannot contain null values, for they are made up of primitive types (int types). These cannot be set to null, as they are not objects. The potential error here is a little bit abstruse, but it is important to note. There is one possible error, namely that the 2D arrays are "ragged"; however we don't need to worry about this for the exam. Still, it is also possible that the array b (presuming that it is not null) is not the same size as the array a. Since we are using a to set our loop counts, this could potentially mean that we overrun the array b by using index values that are too large. (Note, it is also possible that b could be null, causing an error; however, there are no answer choices for that possibility.)

The problematic line in the code above is the one that reads:

ret[i] = a[i];

This is going to work well until the end of the array.  The variable i is going to go for the length of the array a.  However, the array ret is one less in length.  This means that you will overrun your array, getting an ArrayIndexOutOfBoundsException at the very end of the looping.  You would need to implement two indices—one of which will not be incremented on that one time when you skip the element that is removed from the array.

The loop is infinite because i never gets incremented to become greater than count. 

The loop in this case is,

while (i < count) {

  if (i > 0) {

    arr[i] = count;

  }

and the error occurs because there is no terminating factor in the while loop. A terminating factor would be,

while(i<count){

   if(i>0, i<10, i++){

    arr[i] = count;

  }

This loop will indeed run 10 times.  However, notice that it begins on 0 and ends on 10.  Thus, it will begin by executing:

num *= 0

Which is the same as:

num = num * 0 = 0

Thus, you need to start on 1 for i.  However, notice also that you need to go from 1 to 10 inclusive.  Therefore, you need to change i < 10 to i <= 10.

Recall that a "mutator" is a method that allows you to change the value of fields in a class. Now, for the setTime, setMinutes, and setSeconds methods, you do not check several cases of errors. For instance, you could give negative values to all of these methods without causing any errors to be noted. Likewise, you could assign a minute or second value that is greater than 60, which could cause errors as well. Finally, you could even make the clock have a value that is greater than "23:59:59", which does not make much sense at all!

If you notice, in our for loop, the integer j is used as the iteration variable. However, no where in the code is that variable defined. To fix this issue this could have been done.

for (int j=0;j<3,j++)

Note the bold here is inserted. We need to define j here. We could have also defined j as a double.

Type ifstream objects are used to read from files, NOT to write to a file. To write to a file you can use ofstream. You can also you fstream to both read and write to and from a file.

line d's error is that system.out.println (i); is not capitalized.

line e's error is that there is a missing semicolon.