精确数

package test;

public class ChangeType {

 /**
  * @param args
  */
 public static double change(double db,int n){
  //double dbt = db;
  int a = (int) Math.pow(10,n);
  double dbt = Math.floor(db*a)/a;
  //int a = 2^3;
  
//  System.out.println(a);
  return dbt;
 }
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  double aa = ChangeType.change(56.263882212121, 4);
  System.out.println(aa);
 }

}