大数字操作、BigInteger的使用 BigDecimal(很大的小数)

 1 public class Test4 {
 2 public static void main(String[] args) {
 3     BigInteger num1=new BigInteger("123456789123456789123456789");
 4     BigInteger num2=new BigInteger("2345678901234567890");
 5     System.out.println("加："+(num1.add(num2)));
 6     System.out.println("减："+(num1.subtract(num2)));
 7     System.out.println("乘："+(num1.multiply(num2)));
 8     System.out.println("除："+(num1.divide(num2)));
 9     System.out.println("模："+(num1.remainder(num2)));
10     BigInteger[] num3=(num1.divideAndRemainder(num2));
11     for (BigInteger big: num3) {
12         System.out.println("商和余数各为"+big);
13     }
14
15     BigDecimal num4=new BigDecimal("999999999999999999999999999999999999.999999999999999999");
16     BigDecimal num5=new BigDecimal("8999999999999999999999999999999999999999999.999999999999");
17
18     System.out.println("和："+(num4.add(num5)));
19     System.out.println("减："+(num4.subtract(num5)));
20     System.out.println("乘："+(num4.multiply(num5)));
21     System.out.println("除："+(num4.divide(num5,5,BigDecimal.ROUND_HALF_DOWN)));
22
23 }
24 }

在有些项目中需要操作很大的数字的计算，在java中提供了两个常用的类来对大数字进行操作