Problems defining the array for quicksort

Question

import java.io.*;
import java.util.*;
import chn.util.*;
public class Store
          private Item [] myStore;
          public Store (String fileName) {
               fileName = "file50.txt";
/*          public void displayStore ()       
          public String toString () { }
          public void doSort () { }
*/          private void quickSort (Item[] lit, int lo, int hi)   // I don't exactly know what Item[ ] lit will do. please explain it for me.
          int h, l, p, t;
        if (lo < hi) { 
            l = lo;
            h = hi;
      /*      p = a[hi];     //my problem starts with the array 'a' (suppose to be item, but don't know how to modify that.
            do {
                while ((l < h) && (a[l] <= p)) l++;
                while ((h > l) && (a[h] >= p)) h--;
                if (l < h) {
                    t = a[l];
                    a[l] = a[h];
                    a[h] = t;
            } while (l < h);
            t = a[l];
            a[l] = a[hi];
            a[hi] = t;
          private void loadFile (String inFileName)
               FileInput inFile = new FileInput (inFileName = "file50.txt");
}The array 'a' should be replaced with the array 'Item' but some how I'm getting the errors that Item's not a valid type.
for more information, please see http://forum.java.sun.com/thread.jspa?threadID=699397&tstart=60 for more information (the original problem)

Answer 1

Here is what I suggest.
Use collections. I suggest an ArrayList. Using one array involves all sort of messy swapping around which really will make things difficult for you to grasp the basic concept of.
So let us assume a method like this
public void quicksort(List items)
items is a List of Items.
So here is how to write a quicksort
1) If the size of the list is 1 then return the list because it is down to it's final piece and doesn't need to be sorted further
2) Choose a pivot element of your list. The mid point is often chosen for this.
3) Create two new Lists. One for lower elements and one for higher and equal to elements.
4) Go through the list and use compareTo to compare the elements of the list with your pivot element. Take care to skip the pivot element. If elements are less than the pivot put them in the first list. If they are more than or equal to put them in the second list.
5) Recursively call quicksort(list) on the sublists we made.
6) Merge the sublists and pivot values back into one list
7) return the merged list