大数模板Java

import java.util.*;
import java.math.BigInteger;
public class Main{
    public static void  main(String args[]){
        Scanner cin=new Scanner(System.in);
            BigInteger a,b;
            a=cin.nextBigInteger();
            b=cin.nextBigInteger();
            System.out.println(a.add(b));//加法
            System.out.println(a.multiply(b));//乘法
    }
}