bignum3 = bignum1.add(bignum2); //加
bignum3 = bignum1.subtract(bignum2); 减
bignum3 = bignum1.multiply(bignum2); //乘
bignum3 = bignum1.divide(bignum2);//除
操作Float的BigDecimal加减乘除
原文：https://www.cnblogs.com/brxHqs/p/9402542.html
