QuicksortJava.java

public class QuicksortJava {  

 public static void swap(int[] a, int i, int j) {
  int temp = a[i];
  a[i] = a[j];
  a[j] = temp;
 }

 public static void quicksort(int[] a, int L, int R) {
  int m = a[(L + R) / 2];
  int i = L;
  int j = R;
  while (i <= j) {
   while (a[i] < m)
    i++;
   while (a[j] > m)
    j--;
   if (i <= j) {
    swap(a, i, j);
    i++;
    j--;
   }
  }
  if (L < j)
   quicksort(a, L, j);
  if (R > i)
   quicksort(a, i, R);
 }

 public static void quicksort(int[] a) {
  quicksort(a, 0, a.length - 1);
 }

 public static void main(String[] args) {

  // Sample data
  int[] a = new int[10000000];
  for (int i = 0; i < a.length; i++) {
   a[i] = i * 3 / 2 + 1;
   if (i % 3 == 0)
    a[i] = -a[i];
  }

  long t1 = System.currentTimeMillis();
  quicksort(a);
  long t2 = System.currentTimeMillis();
  System.out.println(t2 - t1);

 }

}