Beginner, looking for example for a SortString function

I have started learning Java and the lesson was about strings. I don't understand them well so I tried finding other algorithms to try and learn from them. I found this one but I don't understand it how it works. I know it's something similar to QuickSort method but don't actually understand it.

Here is the code:

1  package junit.runner;
2  
3  import java.util.*;
4  
5  import junit.runner.*;
6  
7  /**
8   * A custom quick sort with support to customize the swap behaviour.
9   * NOTICE: We can't use the the sorting support from the JDK 1.2 collection
10  * classes because of the JDK 1.1.7 compatibility.
11  */
12 public class Sorter {
13     public static interface Swapper {
14         public void swap(Vector values, int left, int right);
15     }
16         
17     public static void sortStrings(Vector values , int left, int right, Swapper swapper) { 
18         int oleft= left;
19         int oright= right;
20         String mid= (String)values.elementAt((left + right) / 2); 
21         do { 
22             while (((String)(values.elementAt(left))).compareTo(mid) < 0)  
23                 left++; 
24             while (mid.compareTo((String)(values.elementAt(right))) < 0)  
25                 right--; 
26             if (left <= right) {
27                 swapper.swap(values, left, right); 
28                 left++; 
29                 right--; 
30             } 
31         } while (left <= right);
32         
33         if (oleft < right) 
34             sortStrings(values, oleft, right, swapper); 
35         if (left < oright) 
36              sortStrings(values, left, oright, swapper); 
37     }
38 }

Here is the link to the function: http://ift.tt/1zWgGaY

If somebody could use an example and describe it I would be really thankful. Thanks in advance.