private void makeTree(int nstep){
  for (Enumeration<Body> e=bodiesRev(); e.hasMoreElements(); ) {
    Body q=e.nextElement();
    if (q.mass != 0.0) {
      q.expandBox(this,nstep);
      MathVector xqic=intcoord(q.pos);
      if (root == null) {
        root=q;
      }
 else {
        root=root.loadTree(q,xqic,Node.IMAX >> 1,this);
      }
    }
  }
  root.hackcofm();
}

private void makeTree ( int nstep ) { for ( Enumeration < Body > e = bodiesRev ( ) ; e . hasMoreElements ( ) ; ) { Body q = e . nextElement ( ) ; if ( q . mass != 0.0 ) { q . expandBox ( this , nstep ) ; MathVector xqic = intcoord ( q . pos ) ; if ( root == null ) { root = q ; } else { root = root . loadTree ( q , xqic , Node . IMAX > > 1 , this ) ; } } } root . hackcofm ( ) ; }
initialize the tree structure for hack force calculation .
