Java中大整数乘法

import java.math.*;

public class BigInt {
    public static void main(String[] args) {
        String s1 = new String("1234567898765432100000");
        String s2 = new String("1234567899999999999999");

        BigInteger bigX = new BigInteger(s1);
        BigInteger bigY = new BigInteger(s2);

        BigInteger bigXY = bigX.multiply(bigY);
        System.out.println(s1+" x "+s2+" = "+bigXY);

    }
}

更详细信息应该查看java api中，java.math.BigInteger;