use sum and multiplication of a BigInteger

Question

I've come across a situation where I have to perform sum and multiplication of the elements of an ArrayList and for this normally I use:

sum+=a.get(i)*b.get(i);

which gives me the exact output I want, but here in my case I've got to do the same with ArrayList of BigInteger type, I've tried it with the below statement, but it is not working as expected.

sum=(a.get(i).multiply(b.get(i))).add(sum);

please let me know how I can do it.

Thanks.

Looks OK for me, but maybe you get your object-references mixed up - but we'll need more context to judge this. — piet.t, Feb 25 '14 at 09:03
a and b both are ArrayList right..? and what abt sum variable.? — Shekhar Khairnar, Feb 25 '14 at 09:08
"it is not working as expected" This tells us nothing. What did you expect and what is it doing? — Peter Lawrey, Feb 25 '14 at 09:10

score 1 · Accepted Answer · edited May 23 '17 at 12:10

Your question is extremely unclear, and as such shouldn't warrant an answer. However, see if the following might help you.

public static void main(String[] args) {
    BigInteger b1 = new BigInteger("1000"), b2 = new BigInteger("1000");
    System.out.println("b1:      " + b1);
    System.out.println("b1 * b2: "+ b1.multiply(b2));
}

Also ensure that you are not falling into the following pit. BigInteger is immutable.

score 0 · Answer 2 · answered Feb 25 '14 at 09:11

0

BigInteger sum = new BigInteger("10");
List<BigInteger> list = new ArrayList<BigInteger>();
list.add(new BigInteger("2"));
list.add(new BigInteger("3"));
sum=(list.get(0).multiply(list.get(1))).add(sum);
System.out.println(sum);

answered Feb 25 '14 at 09:11

Rasool

67
2
5

use sum and multiplication of a BigInteger

2 Answers2