public int multiply(int a,int b){
        int res = 0;
        while(b > 0){
            if(b % 2 != 0){
                res += a;
            }
            a = a<<1;
            b = b>>1;
        }
        return res;
    }
http://www.geeksforgeeks.org/fast-multiplication-method-without-using-multiplication-operator-russian-peasants-algorithm/
Test cases
Division by 0
Negative numbers
src/com/interview/number/RussianPeasantMultiplication.java