How to Implement Heap Sort

package org.best.examples;

class HeapSort

{
public static void main(String arg[]){
 int a[]={3,30,4,12,1,2,34,22,4,3,5,8};
 System.out.println("\n\nInput values:");
 for(int i=0;i<a.length;i++){
  System.out.print(" "+a[i]);
  }
 int N = a.length;
 for (int k = N/2; k > 0; k--) {
     downheap(a, k, N);     
        }
 do {
            int T = a[0];
            a[0] = a[N - 1];
            a[N - 1] = T;
     N = N - 1;
    downheap(a, 1, N);
 } while (N > 1);
    System.out.println("\n\n\nSorted values:");
 for(int i=0;i<a.length;i++)
  {
 System.out.print(" "+a[i]);
     }
}
 static void downheap(int a[], int k, int N) {
 int T = a[k - 1];
 while (k <= N/2) {
            int j = k + k;
            if ((j < N) && (a[j - 1] < a[j])) {
         j++;
     }
     if (T >= a[j - 1]) {
  break;
     } else {
                a[k - 1] = a[j - 1];
                k = j;
            }
 }
        a[k - 1] = T;
 
    }
}