/**
	 * @param v1 除數
	 * @param v2 被除數
	 * @param scale 小數點精度
	 * @return
	 */
	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(Double.toString(v1));  
        BigDecimal b2 = new BigDecimal(Double.toString(v2));  
        return b1.divide(b2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();  
    }