Quick Sort Object Ascending

QuickAscendingSort
Kelas Larik
package LarikSortObject;

/**
 *
 * @author theo
 */
public class QuickAscendingObject {

    public static void quickSort(Object a[]) {
        quickSortHelper(a, 0, a.length - 1);
    }
   
    private static void quickSortHelper( Object x[], int awal, int akhir) {
        if (awal < akhir) {
            //langkah 1
            int i = awal + 1;
            int j = akhir;
            //langkah 2
            while (i <= akhir && (((Comparable) x[i]).compareTo(x[awal]) <= 0)){
                i = i + 1;
            }
            //langkah 3
            while (j > awal && (((Comparable) x[j]).compareTo(x[awal]) >= 0)) {
                j = j - 1;
            }
            //langkah 4
            while (i < j) {
                // langkah 5
                Object temp = x[i];
                x[i] = x[j];
                x[j] = temp;

                // langkah 6
                while (i <= akhir && (((Comparable)x[i]).compareTo(x[awal]) <= 0 )) {
                    i = i + 1;
                }
                // langkah 7
                while (j > awal && (((Comparable)x[j]).compareTo( x[awal]) > 0)) {
                    j = j - 1;
                }
            }
            // langkah 8
            Object temp = x[awal];
            x[awal] = x[j];
            x[j] = temp;

            // langkah 9
            quickSortHelper(x, awal, j - 1);

            // langkah 10
            quickSortHelper(x, j + 1, akhir);
        }
    }
}


Kelas Mahasiswa

package LarikSortObject;

/**
 *
 * @author Theo
 */
public class Mahasiswa implements Comparable{
private int nim;
    private String nama;

    public int getNim() {
        return nim;
    }

    public void setNim(int nim) {
        this.nim = nim;
    }

    public String getNama() {
        return nama;
    }

    public void setNama(String nama) {
        this.nama = nama;
    }

    public int compareTo(Object o) {
       if (nim == ((Mahasiswa) o).nim) {
            return 0;
        } else if (nim < ((Mahasiswa) o).nim) {
            return -1;
        } else {
            return 1;
        }
    }   
}

Kelas Main
package LarikSortObject;

/**
 *
 * @author Theo
 */
public class Mahasiswa implements Comparable{
private int nim;
    private String nama;

    public int getNim() {
        return nim;
    }

    public void setNim(int nim) {
        this.nim = nim;
    }

    public String getNama() {
        return nama;
    }

    public void setNama(String nama) {
        this.nama = nama;
    }

    public int compareTo(Object o) {
       if (nim == ((Mahasiswa) o).nim) {
            return 0;
        } else if (nim < ((Mahasiswa) o).nim) {
            return -1;
        } else {
            return 1;
        }
    }   
}