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Problem of the Day

Wednesday, January 21, 2026

Problem:

Consider the following code, which is intended to print out the average of the integers in an array.

// PRECONDITION:  array length is > 0
int sum = 0;    # sums the values in the integer array
for (int el : arr)
{
    sum += el;
}
double average = sum / arr.length;
System.out.println(average);

Why won't this code work correctly?

  1. it calculates incorrectly for an odd number of values
  2. it calculates incorrectly for an even number of values
  3. it calculates incorrectly if the average is an integer
  4. it calculates incorrectly if the average is not an integer

Show solution:

The correct answer is d. As written, the code uses a division of two integer values, which produces an integer result. For any collection of values where the average is not an integer—the average of 2 and 3 is 2.5, for example—the integer division will not produce the correct result.

Note that storing the result from the integer division in a variable of the type double doesn't help. The integer division has already been performed, so average simply stores that result in double form.