Sorting Runners Into Time Order Shortest First

i need to sort these runners into time order shortest first, the classes both work i just cant get the method sortRunnerList() to work

Java Code:

public class Runner implements Comparable <Runner>
{
/* static variables */
private static int nextNumber;
// To be added by students in Question 3, part (i)(a) and part(iv)(a)
/* instance variables */

private int number; // runner's number
private String name; // runner's name

[Code] .....