Arrays reconsidered

For testing and other purposes it is convenient to provide an additional method returning the array of values being added so far:

/**
 * @return The array of values entered so far
 */
public int[] getValues() {
  ...
  return ...;
}

Provide some tests to assure your sorting implementation works well. You'll implement the actual sorting in the next step. Right now testing for correct sorting will fail (unless a given set of values had already been added in ascending order). A test might look like:

final int[]
  unsortedValues = {0, -1, 5, 2, 7, 6},
    sortedValues = {-1, 0, 2, 5, 6, 7};

IntegerStore store = new IntegerStore();

for (final int i: unsortedValues) {
  store.addValue(i);
}

// Now check your store for correctly sorted order of elements
...

Do not forget to consider value sets which include duplicates and write tests accordingly!

Hint: The Junit Framework provides a (convenience) method assertArrayEquals(...).

Modify your addValue(...) method's implementation. Though there are more elaborate sorting methods available in Java we'll do it the hard way ourselves here. We intend to insert new values at the »right« position to always keep the array sorted. Consider the following sequence:

store.addValue(1);
store.addValue(3);
store.addValue(9);
store.addValue(7);
store.addValue(2);

{1}
{1, 3}
{1, 3, 9}
{1, 3, 7, 9}
{1, 2, 3, 7, 9}

The addValue(...) method now provides a sorting compatible position for inserting. When adding the last value 2 the internal array already contains the sorted values (1, 3, 7, 9). Traversing this array shows that the new value of 2 should be inserted between 1 and 3 and thus at array index 1. The remaining three values 3,7 and 9 each have to be shifted one position to the right.

This way our sequence of values always remains sorted.

Provide a constructor public IntegerStore(final int[] values) in a meaningful way with respect to median calculations.

Add a dummy implementation double getMedian(){return 0;} to your class IntegerStore from exercise Adding support to retrieve statistical data. .

Provide some tests both for even and uneven sample sizes. All of these will probably fail till you complete your implementation.

Finally complete the desired double getMedian() method's implementation and actually test it. Returning a meaningful result requires at least one element:

/**
 * <dl>
 *  <dt><b>Precondition:</b></dt>
 *  <dd>There must be at least one element.</dd>
 * </dl>
 *
 * @return The sample's median.
 */
public double getMedian() {
      ...
  return ... ;
}

Implement a main method as in Reading console input asking the user for an arbitrary number of values. Then compute both their average and median like:

How big is your sample? 5

Enter value #1 of 5: 1
Enter value #2 of 5: -2
Enter value #3 of 5: 1
Enter value #4 of 5: 5
Enter value #5 of 5: 2

Your sample's average is: 1.4
Your sample's median is: 1.0