Java Programming

Hi,

I tried implementing the Heapsort algorithm. Here is my code:

(I'm sorry for the worse looking. In Eclipse I have indented the code.)

The problem is, that an ArrayIndexoutofBoundsException occurs, but I can't find a solution for this problem.

Thanks for help!

public class Heapsort {

 public static void reheap(int [] a, int m, int i) {
  if(2*i<=m) { // a[i] has left son
  int j = 2*i; // a[j] is left son of a[i]
  if(j<m) {
  if(a[j]<a[j+1]) {
  j=j+1;
  }
  }
  if(a[i]<a[j]) {
  int buffer = a[i];
  a[i] = a[j];
  a[j] = buffer;
  }
  else { // heap is correct
  j = m; // breaks
  }
  reheap(a,m,j);
  }
  }

  public static void buildheap(int [] a, int n) {
  for(int i = Math.floorDiv(n,2); i>=0; i--) {
      reheap(a,n,i);
  }
  }

  public static void Heapsort(int [] a, int n) {
  buildheap(a,n);
  for( i = 1; i<n; i++) {

  int buffer = a[1]
      a[1] = a[n+1-i];
  a[n+1-i] = buffer;
    
  reheap(a,n-1,1);
  }
  }

  public static void main(String[] args) {

  int [] a = new int[] {1,8,3,9,5,2,10,7,4};
  Heapsort(a, a.length);

  for(int i=0; i<a.length; i++) {
  System.out.print(a[i]);
  }
  }
}