System.out.println("加法:"+a.add(b));
System.out.println("减法:"+a.subtract(b));
System.out.println("乘法:"+a.multiply(b));
//10:小数点后的位数 RoundingMode.HALF_DOWN:取舍模式
System.out.println("除法:"+a.divide(b,10, RoundingMode.HALF_DOWN));
参考:https://blog.csdn.net/qq_42661906/article/details/110137863