bignum3 = bignum1.add(bignum2); //加
bignum3 = bignum1.subtract(bignum2); 减
bignum3 = bignum1.multiply(bignum2); //乘
bignum3 = bignum1.divide(bignum2);//除
String类型的0.01和float的0.1不能用equals比较，要转换成BigDecimal
totalFee.compareTo((new BigDecimal(wxOrderDto.getTotalPrice()) ==0 //等于0表示相等 1为不相等