@return 两个参数的商
*/
public static String divide(String v1, String v2, int scale) {
if (scale < 0) {
throw new IllegalArgumentException("The scale must be a positive integer or zero");
}
BigDecimal b1 = new BigDecimal(v1);
BigDecimal b2 = new BigDecimal(v1); //都写成v1了
return b1.divide(b2, scale, BigDecimal.ROUND_HALF_UP).toString();
}
/**