近似求PI的值

package lyt;

import javax.swing.JOptionPane;

public class Lyt4 {

 
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  double sum=0,s=-1;
  for(long i=1;i<99999999;i++)
  {
   s=-s;
   sum=sum+1.0/(2*i-1)*s;
  }
  JOptionPane.showMessageDialog(null, "PI = " + 4*sum,"ÁºÑàæÃ",JOptionPane.INFORMATION_MESSAGE);
  }

 }