blic class Arith {  
  private static final int DEF_DIV_SCALE = 10;  
    
  /** 
   * 两个Double数相加 
   * @param v1 
   * @param v2 
   * @return Double 
   */  
  public static Double add(Double v1,Double v2){  
      BigDecimal b1 = new BigDecimal(v1.toString());  
      BigDecimal b2 = new BigDecimal(v2.toString());  
      return b1.add(b2).doubleValue();  
  }  
    
  /** 
   * 两个Double数相减 
   * @param v1 
   * @param v2 
   * @return Double 
   */  
  public static Double sub(Double v1,Double v2){  
      BigDecimal b1 = new BigDecimal(v1.toString());  
      BigDecimal b2 = new BigDecimal(v2.toString());  
      return b1.subtract(b2).doubleValue();  
  }  
    
  /** 
   * 两个Double数相乘 
   * @param v1 
   * @param v2 
   * @return Double 
   */  
  public static Double mul(Double v1,Double v2){  
      BigDecimal b1 = new BigDecimal(v1.toString());  
      BigDecimal b2 = new BigDecimal(v2.toString());  
      return b1.multiply(b2).doubleValue();  
  }  
    
  /** 
   * 两个Double数相除 
   * @param v1 
   * @param v2 
   * @return Double 
   */  
  public static Double div(Double v1,Double v2){  
      BigDecimal b1 = new BigDecimal(v1.toString());  
      BigDecimal b2 = new BigDecimal(v2.toString());  
      return b1.divide(b2,DEF_DIV_SCALE,BigDecimal.ROUND_HALF_UP).doubleValue();  
  }  
    
  /** 
   * 两个Double数相除，并保留scale位小数 
   * @param v1 
   * @param v2 
   * @param scale 
   * @return Double 
   */  
  public static Double div(Double v1,Double v2,int scale){  
      if(scale<0){  
          throw new IllegalArgumentException(  
          "The scale must be a positive integer or zero");  
      }  
      BigDecimal b1 = new BigDecimal(v1.toString());  
      BigDecimal b2 = new BigDecimal(v2.toString());  
      return b1.divide(b2,scale,BigDecimal.ROUND_HALF_UP).doubleValue();  
  }