It’s all a matter of adequate storage and algorithms to treat numbers as smaller parts. Let’s assume you have a compiler in which an int can only be 0 through 99 and you want to handle numbers up to 999999 (we’ll only worry about positive numbers here to keep it simple). You do that by … Read more
The method you want is BigInteger#valueOf(long val). E.g., BigInteger bi = BigInteger.valueOf(myInteger.intValue()); Making a String first is unnecessary and undesired.
BigInteger is immutable. The javadocs states that add() “[r]eturns a BigInteger whose value is (this + val).” Therefore, you can’t change sum, you need to reassign the result of the add method to sum variable. sum = sum.add(BigInteger.valueOf(i));