java精确数目字计算

import java.math.BigDecimal;

public class MathExtend {

 // 默认除法运算精度
 private static final int DEFAULT_DIV_SCALE = 10;

 public static double add(double v1, double v2)
 {
  BigDecimal b1 = new BigDecimal(Double.toString(v1));
  BigDecimal b2 = new BigDecimal(Double.toString(v2));
  return b1.add(b2).doubleValue();
 }

 public static String add(String v1, String v2)
 {
  BigDecimal b1 = new BigDecimal(v1);
  BigDecimal b2 = new BigDecimal(v2);
  return b1.add(b2).toString();
 }

 public static double subtract(double v1, double v2)
 {
  BigDecimal b1 = new BigDecimal(Double.toString(v1));
  BigDecimal b2 = new BigDecimal(Double.toString(v2));
  return b1.subtract(b2).doubleValue();
 }

 public static String subtract(String v1, String v2)
 {
  BigDecimal b1 = new BigDecimal(v1);
  BigDecimal b2 = new BigDecimal(v2);
  return b1.subtract(b2).toString();
 }

 public static double multiply(double v1, double v2)
 {
  BigDecimal b1 = new BigDecimal(Double.toString(v1));
  BigDecimal b2 = new BigDecimal(Double.toString(v2));
  return b1.multiply(b2).doubleValue();
 }

 public static String multiply(String v1, String v2)
 {

  BigDecimal b1 = new BigDecimal(v1);
  BigDecimal b2 = new BigDecimal(v2);

  return b1.multiply(b2).toString();
 }

 public static double divide(double v1, double v2)
 {
  return divide(v1, v2, DEFAULT_DIV_SCALE);
 }

 public static double divide(double v1, double v2, int scale)
 {

  return divide(v1, v2, scale, BigDecimal.ROUND_HALF_UP);
 }

 public static double divide(double v1, double v2, int scale, int round_mode) {
  if (scale < 0)

  {
   throw new IllegalArgumentException(
     "The scale must be a positive integer or zero");
  }

  BigDecimal b1 = new BigDecimal(Double.toString(v1));
  BigDecimal b2 = new BigDecimal(Double.toString(v2));

  return b1.divide(b2, scale, round_mode).doubleValue();
 }

 public static String divide(String v1, String v2)
 {
  return divide(v1, v2, DEFAULT_DIV_SCALE);
 }

 public static String divide(String v1, String v2, int scale)
 {
  return divide(v1, v2, DEFAULT_DIV_SCALE, BigDecimal.ROUND_HALF_UP);
 }

 public static String divide(String v1, String v2, int scale, int round_mode)
 {
  if (scale < 0)

  {
   throw new IllegalArgumentException(
     "The scale must be a positive integer or zero");
  }

  BigDecimal b1 = new BigDecimal(v1);
  BigDecimal b2 = new BigDecimal(v2);

  return b1.divide(b2, scale, round_mode).toString();
 }

 public static double round(double v, int scale)
 {
  return round(v, scale, BigDecimal.ROUND_HALF_UP);
 }

 public static double round(double v, int scale, int round_mode)
 {
  if (scale < 0)

  {
   throw new IllegalArgumentException(
     "The scale must be a positive integer or zero");
  }

  BigDecimal b = new BigDecimal(Double.toString(v));
  return b.setScale(scale, round_mode).doubleValue();
 }

 public static String round(String v, int scale)
 {
  return round(v, scale, BigDecimal.ROUND_HALF_UP);
 }

 public static String round(String v, int scale, int round_mode)
 {
  if (scale < 0)
  {
   throw new IllegalArgumentException(
     "The scale must be a positive integer or zero");
  }
  BigDecimal b = new BigDecimal(v);
  return b.setScale(scale, round_mode).toString();
 }
 
 public static void main(String[] args)throws Exception{
  System.out.println(divide(10, 3, 3, BigDecimal.ROUND_HALF_UP));
 }
}